From: Paul Mundt <lethal@linux-sh.org>
Date: Tue, 16 Nov 2010 05:00:24 +0000 (+0900)
Subject: fbdev: move udlfb out of staging.
X-Git-Tag: firefly_0821_release~7613^2~3120^2~1^2~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=96f8d864afd646e4a52ea55462b7d83e3b94fd5c;p=firefly-linux-kernel-4.4.55.git

fbdev: move udlfb out of staging.

udlfb has undergone a fair bit of cleanup recently and is effectively at
the point where it can be liberated from staging purgatory and promoted
to a real driver.

The outstanding cleanups are all minor, with some of them dependent on
drivers/video headers, so these will be done incrementally from udlfb's
new home.

Requested-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
---

diff --git a/Documentation/fb/udlfb.txt b/Documentation/fb/udlfb.txt
new file mode 100644
index 000000000000..7fdde2a02a27
--- /dev/null
+++ b/Documentation/fb/udlfb.txt
@@ -0,0 +1,144 @@
+
+What is udlfb?
+===============
+
+This is a driver for DisplayLink USB 2.0 era graphics chips.
+
+DisplayLink chips provide simple hline/blit operations with some compression,
+pairing that with a hardware framebuffer (16MB) on the other end of the
+USB wire.  That hardware framebuffer is able to drive the VGA, DVI, or HDMI
+monitor with no CPU involvement until a pixel has to change.
+
+The CPU or other local resource does all the rendering; optinally compares the
+result with a local shadow of the remote hardware framebuffer to identify
+the minimal set of pixels that have changed; and compresses and sends those
+pixels line-by-line via USB bulk transfers.
+
+Because of the efficiency of bulk transfers and a protocol on top that
+does not require any acks - the effect is very low latency that
+can support surprisingly high resolutions with good performance for
+non-gaming and non-video applications.
+
+Mode setting, EDID read, etc are other bulk or control transfers. Mode
+setting is very flexible - able to set nearly arbitrary modes from any timing.
+
+Advantages of USB graphics in general:
+
+ * Ability to add a nearly arbitrary number of displays to any USB 2.0
+   capable system. On Linux, number of displays is limited by fbdev interface
+   (FB_MAX is currently 32). Of course, all USB devices on the same
+   host controller share the same 480Mbs USB 2.0 interface.
+
+Advantages of supporting DisplayLink chips with kernel framebuffer interface:
+
+ * The actual hardware functionality of DisplayLink chips matches nearly
+   one-to-one with the fbdev interface, making the driver quite small and
+   tight relative to the functionality it provides.
+ * X servers and other applications can use the standard fbdev interface
+   from user mode to talk to the device, without needing to know anything
+   about USB or DisplayLink's protocol at all. A "displaylink" X driver
+   and a slightly modified "fbdev" X driver are among those that already do.
+
+Disadvantages:
+
+ * Fbdev's mmap interface assumes a real hardware framebuffer is mapped.
+   In the case of USB graphics, it is just an allocated (virtual) buffer.
+   Writes need to be detected and encoded into USB bulk transfers by the CPU.
+   Accurate damage/changed area notifications work around this problem.
+   In the future, hopefully fbdev will be enhanced with an small standard
+   interface to allow mmap clients to report damage, for the benefit
+   of virtual or remote framebuffers.
+ * Fbdev does not arbitrate client ownership of the framebuffer well.
+ * Fbcon assumes the first framebuffer it finds should be consumed for console.
+ * It's not clear what the future of fbdev is, given the rise of KMS/DRM.
+
+How to use it?
+==============
+
+Udlfb, when loaded as a module, will match against all USB 2.0 generation
+DisplayLink chips (Alex and Ollie family). It will then attempt to read the EDID
+of the monitor, and set the best common mode between the DisplayLink device
+and the monitor's capabilities.
+
+If the DisplayLink device is successful, it will paint a "green screen" which
+means that from a hardware and fbdev software perspective, everything is good.
+
+At that point, a /dev/fb? interface will be present for user-mode applications
+to open and begin writing to the framebuffer of the DisplayLink device using
+standard fbdev calls.  Note that if mmap() is used, by default the user mode
+application must send down damage notifcations to trigger repaints of the
+changed regions.  Alternatively, udlfb can be recompiled with experimental
+defio support enabled, to support a page-fault based detection mechanism
+that can work without explicit notifcation.
+
+The most common client of udlfb is xf86-video-displaylink or a modified
+xf86-video-fbdev X server. These servers have no real DisplayLink specific
+code. They write to the standard framebuffer interface and rely on udlfb
+to do its thing.  The one extra feature they have is the ability to report
+rectangles from the X DAMAGE protocol extension down to udlfb via udlfb's
+damage interface (which will hopefully be standardized for all virtual
+framebuffers that need damage info). These damage notifications allow
+udlfb to efficiently process the changed pixels.
+
+Module Options
+==============
+
+Special configuration for udlfb is usually unnecessary. There are a few
+options, however.
+
+From the command line, pass options to modprobe
+modprobe udlfb defio=1 console=1
+
+Or for permanent option, create file like /etc/modprobe.d/options with text
+options udlfb defio=1 console=1
+
+Accepted options:
+
+fb_defio	Make use of the fb_defio (CONFIG_FB_DEFERRED_IO) kernel
+		module to track changed areas of the framebuffer by page faults.
+        	Standard fbdev applications that use mmap but that do not
+		report damage, may be able to work with this enabled.
+		Disabled by default because of overhead and other issues.
+
+console		Allow fbcon to attach to udlfb provided framebuffers. This
+		is disabled by default because fbcon will aggressively consume
+		the first framebuffer it finds, which isn't usually what the
+		user wants in the case of USB displays.
+
+Sysfs Attributes
+================
+
+Udlfb creates several files in /sys/class/graphics/fb?
+Where ? is the sequential framebuffer id of the particular DisplayLink device
+
+edid	       		If a valid EDID blob is written to this file (typically
+			by a udev rule), then udlfb will use this EDID as a
+			backup in case reading the actual EDID of the monitor
+			attached to the DisplayLink device fails. This is
+			especially useful for fixed panels, etc. that cannot
+			communicate their capabilities via EDID. Reading
+			this file returns the current EDID of the attached
+			monitor (or last backup value written). This is
+			useful to get the EDID of the attached monitor,
+			which can be passed to utilities like parse-edid.
+
+metrics_bytes_rendered	32-bit count of pixel bytes rendered
+
+metrics_bytes_identical 32-bit count of how many of those bytes were found to be
+			unchanged, based on a shadow framebuffer check
+
+metrics_bytes_sent	32-bit count of how many bytes were transferred over
+			USB to communicate the resulting changed pixels to the
+			hardware. Includes compression and protocol overhead
+
+metrics_cpu_kcycles_used 32-bit count of CPU cycles used in processing the
+			above pixels (in thousands of cycles).
+
+metrics_reset		Write-only. Any write to this file resets all metrics
+			above to zero.  Note that the 32-bit counters above
+			roll over very quickly. To get reliable results, design
+			performance tests to start and finish in a very short
+			period of time (one minute or less is safe).
+
+--
+Bernie Thompson <bernie@plugable.com>
diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index 5eafdf435550..df31a7228079 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -111,8 +111,6 @@ source "drivers/staging/vt6655/Kconfig"
 
 source "drivers/staging/vt6656/Kconfig"
 
-source "drivers/staging/udlfb/Kconfig"
-
 source "drivers/staging/hv/Kconfig"
 
 source "drivers/staging/vme/Kconfig"
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index a97a955c094b..7a15c0c82b69 100644
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -38,7 +38,6 @@ obj-$(CONFIG_USB_SERIAL_QUATECH_USB2)	+= quatech_usb2/
 obj-$(CONFIG_OCTEON_ETHERNET)	+= octeon/
 obj-$(CONFIG_VT6655)		+= vt6655/
 obj-$(CONFIG_VT6656)		+= vt6656/
-obj-$(CONFIG_FB_UDL)		+= udlfb/
 obj-$(CONFIG_HYPERV)		+= hv/
 obj-$(CONFIG_VME_BUS)		+= vme/
 obj-$(CONFIG_MRST_RAR_HANDLER)	+= memrar/
diff --git a/drivers/staging/udlfb/Kconfig b/drivers/staging/udlfb/Kconfig
deleted file mode 100644
index 65bd5db4ca56..000000000000
--- a/drivers/staging/udlfb/Kconfig
+++ /dev/null
@@ -1,14 +0,0 @@
-config FB_UDL
-	tristate "Displaylink USB Framebuffer support"
-	depends on FB && USB
-	select FB_MODE_HELPERS
-	select FB_SYS_FILLRECT
-	select FB_SYS_COPYAREA
-	select FB_SYS_IMAGEBLIT
-	select FB_SYS_FOPS
-	select FB_DEFERRED_IO
-	---help---
-	  This is a kernel framebuffer driver for DisplayLink USB devices.
-	  Supports fbdev clients like xf86-video-fbdev, kdrive, fbi, and
-	  mplayer -vo fbdev. Supports all USB 2.0 era DisplayLink devices.
-	  To compile as a module, choose M here: the module name is udlfb.
diff --git a/drivers/staging/udlfb/Makefile b/drivers/staging/udlfb/Makefile
deleted file mode 100644
index 30d9e675b10f..000000000000
--- a/drivers/staging/udlfb/Makefile
+++ /dev/null
@@ -1 +0,0 @@
-obj-$(CONFIG_FB_UDL)		+= udlfb.o
diff --git a/drivers/staging/udlfb/udlfb.c b/drivers/staging/udlfb/udlfb.c
deleted file mode 100644
index fed25105970a..000000000000
--- a/drivers/staging/udlfb/udlfb.c
+++ /dev/null
@@ -1,1916 +0,0 @@
-/*
- * udlfb.c -- Framebuffer driver for DisplayLink USB controller
- *
- * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
- * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
- * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License v2. See the file COPYING in the main directory of this archive for
- * more details.
- *
- * Layout is based on skeletonfb by James Simmons and Geert Uytterhoeven,
- * usb-skeleton by GregKH.
- *
- * Device-specific portions based on information from Displaylink, with work
- * from Florian Echtler, Henrik Bjerregaard Pedersen, and others.
- */
-
-#include <linux/module.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/usb.h>
-#include <linux/uaccess.h>
-#include <linux/mm.h>
-#include <linux/fb.h>
-#include <linux/vmalloc.h>
-#include <linux/slab.h>
-#include <linux/delay.h>
-
-#include "udlfb.h"
-
-static struct fb_fix_screeninfo dlfb_fix = {
-	.id =           "udlfb",
-	.type =         FB_TYPE_PACKED_PIXELS,
-	.visual =       FB_VISUAL_TRUECOLOR,
-	.xpanstep =     0,
-	.ypanstep =     0,
-	.ywrapstep =    0,
-	.accel =        FB_ACCEL_NONE,
-};
-
-static const u32 udlfb_info_flags = FBINFO_DEFAULT | FBINFO_READS_FAST |
-#ifdef FBINFO_VIRTFB
-		FBINFO_VIRTFB |
-#endif
-		FBINFO_HWACCEL_IMAGEBLIT | FBINFO_HWACCEL_FILLRECT |
-		FBINFO_HWACCEL_COPYAREA | FBINFO_MISC_ALWAYS_SETPAR;
-
-/*
- * There are many DisplayLink-based products, all with unique PIDs. We are able
- * to support all volume ones (circa 2009) with a single driver, so we match
- * globally on VID. TODO: Probe() needs to detect when we might be running
- * "future" chips, and bail on those, so a compatible driver can match.
- */
-static struct usb_device_id id_table[] = {
-	{.idVendor = 0x17e9, .match_flags = USB_DEVICE_ID_MATCH_VENDOR,},
-	{},
-};
-MODULE_DEVICE_TABLE(usb, id_table);
-
-/* module options */
-static int console;   /* Optionally allow fbcon to consume first framebuffer */
-static int fb_defio;  /* Optionally enable experimental fb_defio mmap support */
-
-/* dlfb keeps a list of urbs for efficient bulk transfers */
-static void dlfb_urb_completion(struct urb *urb);
-static struct urb *dlfb_get_urb(struct dlfb_data *dev);
-static int dlfb_submit_urb(struct dlfb_data *dev, struct urb * urb, size_t len);
-static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size);
-static void dlfb_free_urb_list(struct dlfb_data *dev);
-
-/*
- * All DisplayLink bulk operations start with 0xAF, followed by specific code
- * All operations are written to buffers which then later get sent to device
- */
-static char *dlfb_set_register(char *buf, u8 reg, u8 val)
-{
-	*buf++ = 0xAF;
-	*buf++ = 0x20;
-	*buf++ = reg;
-	*buf++ = val;
-	return buf;
-}
-
-static char *dlfb_vidreg_lock(char *buf)
-{
-	return dlfb_set_register(buf, 0xFF, 0x00);
-}
-
-static char *dlfb_vidreg_unlock(char *buf)
-{
-	return dlfb_set_register(buf, 0xFF, 0xFF);
-}
-
-/*
- * On/Off for driving the DisplayLink framebuffer to the display
- *  0x00 H and V sync on
- *  0x01 H and V sync off (screen blank but powered)
- *  0x07 DPMS powerdown (requires modeset to come back)
- */
-static char *dlfb_enable_hvsync(char *buf, bool enable)
-{
-	if (enable)
-		return dlfb_set_register(buf, 0x1F, 0x00);
-	else
-		return dlfb_set_register(buf, 0x1F, 0x07);
-}
-
-static char *dlfb_set_color_depth(char *buf, u8 selection)
-{
-	return dlfb_set_register(buf, 0x00, selection);
-}
-
-static char *dlfb_set_base16bpp(char *wrptr, u32 base)
-{
-	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
-	wrptr = dlfb_set_register(wrptr, 0x20, base >> 16);
-	wrptr = dlfb_set_register(wrptr, 0x21, base >> 8);
-	return dlfb_set_register(wrptr, 0x22, base);
-}
-
-/*
- * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
- * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
- */
-static char *dlfb_set_base8bpp(char *wrptr, u32 base)
-{
-	wrptr = dlfb_set_register(wrptr, 0x26, base >> 16);
-	wrptr = dlfb_set_register(wrptr, 0x27, base >> 8);
-	return dlfb_set_register(wrptr, 0x28, base);
-}
-
-static char *dlfb_set_register_16(char *wrptr, u8 reg, u16 value)
-{
-	wrptr = dlfb_set_register(wrptr, reg, value >> 8);
-	return dlfb_set_register(wrptr, reg+1, value);
-}
-
-/*
- * This is kind of weird because the controller takes some
- * register values in a different byte order than other registers.
- */
-static char *dlfb_set_register_16be(char *wrptr, u8 reg, u16 value)
-{
-	wrptr = dlfb_set_register(wrptr, reg, value);
-	return dlfb_set_register(wrptr, reg+1, value >> 8);
-}
-
-/*
- * LFSR is linear feedback shift register. The reason we have this is
- * because the display controller needs to minimize the clock depth of
- * various counters used in the display path. So this code reverses the
- * provided value into the lfsr16 value by counting backwards to get
- * the value that needs to be set in the hardware comparator to get the
- * same actual count. This makes sense once you read above a couple of
- * times and think about it from a hardware perspective.
- */
-static u16 dlfb_lfsr16(u16 actual_count)
-{
-	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */
-
-	while (actual_count--) {
-		lv =	 ((lv << 1) |
-			(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
-			& 0xFFFF;
-	}
-
-	return (u16) lv;
-}
-
-/*
- * This does LFSR conversion on the value that is to be written.
- * See LFSR explanation above for more detail.
- */
-static char *dlfb_set_register_lfsr16(char *wrptr, u8 reg, u16 value)
-{
-	return dlfb_set_register_16(wrptr, reg, dlfb_lfsr16(value));
-}
-
-/*
- * This takes a standard fbdev screeninfo struct and all of its monitor mode
- * details and converts them into the DisplayLink equivalent register commands.
- */
-static char *dlfb_set_vid_cmds(char *wrptr, struct fb_var_screeninfo *var)
-{
-	u16 xds, yds;
-	u16 xde, yde;
-	u16 yec;
-
-	/* x display start */
-	xds = var->left_margin + var->hsync_len;
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x01, xds);
-	/* x display end */
-	xde = xds + var->xres;
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x03, xde);
-
-	/* y display start */
-	yds = var->upper_margin + var->vsync_len;
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x05, yds);
-	/* y display end */
-	yde = yds + var->yres;
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x07, yde);
-
-	/* x end count is active + blanking - 1 */
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x09,
-			xde + var->right_margin - 1);
-
-	/* libdlo hardcodes hsync start to 1 */
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0B, 1);
-
-	/* hsync end is width of sync pulse + 1 */
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0D, var->hsync_len + 1);
-
-	/* hpixels is active pixels */
-	wrptr = dlfb_set_register_16(wrptr, 0x0F, var->xres);
-
-	/* yendcount is vertical active + vertical blanking */
-	yec = var->yres + var->upper_margin + var->lower_margin +
-			var->vsync_len;
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x11, yec);
-
-	/* libdlo hardcodes vsync start to 0 */
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x13, 0);
-
-	/* vsync end is width of vsync pulse */
-	wrptr = dlfb_set_register_lfsr16(wrptr, 0x15, var->vsync_len);
-
-	/* vpixels is active pixels */
-	wrptr = dlfb_set_register_16(wrptr, 0x17, var->yres);
-
-	/* convert picoseconds to 5kHz multiple for pclk5k = x * 1E12/5k */
-	wrptr = dlfb_set_register_16be(wrptr, 0x1B,
-			200*1000*1000/var->pixclock);
-
-	return wrptr;
-}
-
-/*
- * This takes a standard fbdev screeninfo struct that was fetched or prepared
- * and then generates the appropriate command sequence that then drives the
- * display controller.
- */
-static int dlfb_set_video_mode(struct dlfb_data *dev,
-				struct fb_var_screeninfo *var)
-{
-	char *buf;
-	char *wrptr;
-	int retval = 0;
-	int writesize;
-	struct urb *urb;
-
-	if (!atomic_read(&dev->usb_active))
-		return -EPERM;
-
-	urb = dlfb_get_urb(dev);
-	if (!urb)
-		return -ENOMEM;
-
-	buf = (char *) urb->transfer_buffer;
-
-	/*
-	* This first section has to do with setting the base address on the
-	* controller * associated with the display. There are 2 base
-	* pointers, currently, we only * use the 16 bpp segment.
-	*/
-	wrptr = dlfb_vidreg_lock(buf);
-	wrptr = dlfb_set_color_depth(wrptr, 0x00);
-	/* set base for 16bpp segment to 0 */
-	wrptr = dlfb_set_base16bpp(wrptr, 0);
-	/* set base for 8bpp segment to end of fb */
-	wrptr = dlfb_set_base8bpp(wrptr, dev->info->fix.smem_len);
-
-	wrptr = dlfb_set_vid_cmds(wrptr, var);
-	wrptr = dlfb_enable_hvsync(wrptr, true);
-	wrptr = dlfb_vidreg_unlock(wrptr);
-
-	writesize = wrptr - buf;
-
-	retval = dlfb_submit_urb(dev, urb, writesize);
-
-	return retval;
-}
-
-static int dlfb_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)
-{
-	unsigned long start = vma->vm_start;
-	unsigned long size = vma->vm_end - vma->vm_start;
-	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
-	unsigned long page, pos;
-
-	if (offset + size > info->fix.smem_len)
-		return -EINVAL;
-
-	pos = (unsigned long)info->fix.smem_start + offset;
-
-	dl_notice("mmap() framebuffer addr:%lu size:%lu\n",
-		  pos, size);
-
-	while (size > 0) {
-		page = vmalloc_to_pfn((void *)pos);
-		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
-			return -EAGAIN;
-
-		start += PAGE_SIZE;
-		pos += PAGE_SIZE;
-		if (size > PAGE_SIZE)
-			size -= PAGE_SIZE;
-		else
-			size = 0;
-	}
-
-	vma->vm_flags |= VM_RESERVED;	/* avoid to swap out this VMA */
-	return 0;
-}
-
-/*
- * Trims identical data from front and back of line
- * Sets new front buffer address and width
- * And returns byte count of identical pixels
- * Assumes CPU natural alignment (unsigned long)
- * for back and front buffer ptrs and width
- */
-static int dlfb_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
-{
-	int j, k;
-	const unsigned long *back = (const unsigned long *) bback;
-	const unsigned long *front = (const unsigned long *) *bfront;
-	const int width = *width_bytes / sizeof(unsigned long);
-	int identical = width;
-	int start = width;
-	int end = width;
-
-	prefetch((void *) front);
-	prefetch((void *) back);
-
-	for (j = 0; j < width; j++) {
-		if (back[j] != front[j]) {
-			start = j;
-			break;
-		}
-	}
-
-	for (k = width - 1; k > j; k--) {
-		if (back[k] != front[k]) {
-			end = k+1;
-			break;
-		}
-	}
-
-	identical = start + (width - end);
-	*bfront = (u8 *) &front[start];
-	*width_bytes = (end - start) * sizeof(unsigned long);
-
-	return identical * sizeof(unsigned long);
-}
-
-/*
- * Render a command stream for an encoded horizontal line segment of pixels.
- *
- * A command buffer holds several commands.
- * It always begins with a fresh command header
- * (the protocol doesn't require this, but we enforce it to allow
- * multiple buffers to be potentially encoded and sent in parallel).
- * A single command encodes one contiguous horizontal line of pixels
- *
- * The function relies on the client to do all allocation, so that
- * rendering can be done directly to output buffers (e.g. USB URBs).
- * The function fills the supplied command buffer, providing information
- * on where it left off, so the client may call in again with additional
- * buffers if the line will take several buffers to complete.
- *
- * A single command can transmit a maximum of 256 pixels,
- * regardless of the compression ratio (protocol design limit).
- * To the hardware, 0 for a size byte means 256
- *
- * Rather than 256 pixel commands which are either rl or raw encoded,
- * the rlx command simply assumes alternating raw and rl spans within one cmd.
- * This has a slightly larger header overhead, but produces more even results.
- * It also processes all data (read and write) in a single pass.
- * Performance benchmarks of common cases show it having just slightly better
- * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
- * But for very rl friendly data, will compress not quite as well.
- */
-static void dlfb_compress_hline(
-	const uint16_t **pixel_start_ptr,
-	const uint16_t *const pixel_end,
-	uint32_t *device_address_ptr,
-	uint8_t **command_buffer_ptr,
-	const uint8_t *const cmd_buffer_end)
-{
-	const uint16_t *pixel = *pixel_start_ptr;
-	uint32_t dev_addr  = *device_address_ptr;
-	uint8_t *cmd = *command_buffer_ptr;
-	const int bpp = 2;
-
-	while ((pixel_end > pixel) &&
-	       (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
-		uint8_t *raw_pixels_count_byte = 0;
-		uint8_t *cmd_pixels_count_byte = 0;
-		const uint16_t *raw_pixel_start = 0;
-		const uint16_t *cmd_pixel_start, *cmd_pixel_end = 0;
-
-		prefetchw((void *) cmd); /* pull in one cache line at least */
-
-		*cmd++ = 0xAF;
-		*cmd++ = 0x6B;
-		*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
-		*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
-		*cmd++ = (uint8_t) ((dev_addr) & 0xFF);
-
-		cmd_pixels_count_byte = cmd++; /*  we'll know this later */
-		cmd_pixel_start = pixel;
-
-		raw_pixels_count_byte = cmd++; /*  we'll know this later */
-		raw_pixel_start = pixel;
-
-		cmd_pixel_end = pixel + min(MAX_CMD_PIXELS + 1,
-			min((int)(pixel_end - pixel),
-			    (int)(cmd_buffer_end - cmd) / bpp));
-
-		prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
-
-		while (pixel < cmd_pixel_end) {
-			const uint16_t * const repeating_pixel = pixel;
-
-			*(uint16_t *)cmd = cpu_to_be16p(pixel);
-			cmd += 2;
-			pixel++;
-
-			if (unlikely((pixel < cmd_pixel_end) &&
-				     (*pixel == *repeating_pixel))) {
-				/* go back and fill in raw pixel count */
-				*raw_pixels_count_byte = ((repeating_pixel -
-						raw_pixel_start) + 1) & 0xFF;
-
-				while ((pixel < cmd_pixel_end)
-				       && (*pixel == *repeating_pixel)) {
-					pixel++;
-				}
-
-				/* immediately after raw data is repeat byte */
-				*cmd++ = ((pixel - repeating_pixel) - 1) & 0xFF;
-
-				/* Then start another raw pixel span */
-				raw_pixel_start = pixel;
-				raw_pixels_count_byte = cmd++;
-			}
-		}
-
-		if (pixel > raw_pixel_start) {
-			/* finalize last RAW span */
-			*raw_pixels_count_byte = (pixel-raw_pixel_start) & 0xFF;
-		}
-
-		*cmd_pixels_count_byte = (pixel - cmd_pixel_start) & 0xFF;
-		dev_addr += (pixel - cmd_pixel_start) * bpp;
-	}
-
-	if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
-		/* Fill leftover bytes with no-ops */
-		if (cmd_buffer_end > cmd)
-			memset(cmd, 0xAF, cmd_buffer_end - cmd);
-		cmd = (uint8_t *) cmd_buffer_end;
-	}
-
-	*command_buffer_ptr = cmd;
-	*pixel_start_ptr = pixel;
-	*device_address_ptr = dev_addr;
-
-	return;
-}
-
-/*
- * There are 3 copies of every pixel: The front buffer that the fbdev
- * client renders to, the actual framebuffer across the USB bus in hardware
- * (that we can only write to, slowly, and can never read), and (optionally)
- * our shadow copy that tracks what's been sent to that hardware buffer.
- */
-static int dlfb_render_hline(struct dlfb_data *dev, struct urb **urb_ptr,
-			      const char *front, char **urb_buf_ptr,
-			      u32 byte_offset, u32 byte_width,
-			      int *ident_ptr, int *sent_ptr)
-{
-	const u8 *line_start, *line_end, *next_pixel;
-	u32 dev_addr = dev->base16 + byte_offset;
-	struct urb *urb = *urb_ptr;
-	u8 *cmd = *urb_buf_ptr;
-	u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
-
-	line_start = (u8 *) (front + byte_offset);
-	next_pixel = line_start;
-	line_end = next_pixel + byte_width;
-
-	if (dev->backing_buffer) {
-		int offset;
-		const u8 *back_start = (u8 *) (dev->backing_buffer
-						+ byte_offset);
-
-		*ident_ptr += dlfb_trim_hline(back_start, &next_pixel,
-			&byte_width);
-
-		offset = next_pixel - line_start;
-		line_end = next_pixel + byte_width;
-		dev_addr += offset;
-		back_start += offset;
-		line_start += offset;
-
-		memcpy((char *)back_start, (char *) line_start,
-		       byte_width);
-	}
-
-	while (next_pixel < line_end) {
-
-		dlfb_compress_hline((const uint16_t **) &next_pixel,
-			     (const uint16_t *) line_end, &dev_addr,
-			(u8 **) &cmd, (u8 *) cmd_end);
-
-		if (cmd >= cmd_end) {
-			int len = cmd - (u8 *) urb->transfer_buffer;
-			if (dlfb_submit_urb(dev, urb, len))
-				return 1; /* lost pixels is set */
-			*sent_ptr += len;
-			urb = dlfb_get_urb(dev);
-			if (!urb)
-				return 1; /* lost_pixels is set */
-			*urb_ptr = urb;
-			cmd = urb->transfer_buffer;
-			cmd_end = &cmd[urb->transfer_buffer_length];
-		}
-	}
-
-	*urb_buf_ptr = cmd;
-
-	return 0;
-}
-
-int dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
-	       int width, int height, char *data)
-{
-	int i, ret;
-	char *cmd;
-	cycles_t start_cycles, end_cycles;
-	int bytes_sent = 0;
-	int bytes_identical = 0;
-	struct urb *urb;
-	int aligned_x;
-
-	start_cycles = get_cycles();
-
-	aligned_x = DL_ALIGN_DOWN(x, sizeof(unsigned long));
-	width = DL_ALIGN_UP(width + (x-aligned_x), sizeof(unsigned long));
-	x = aligned_x;
-
-	if ((width <= 0) ||
-	    (x + width > dev->info->var.xres) ||
-	    (y + height > dev->info->var.yres))
-		return -EINVAL;
-
-	if (!atomic_read(&dev->usb_active))
-		return 0;
-
-	urb = dlfb_get_urb(dev);
-	if (!urb)
-		return 0;
-	cmd = urb->transfer_buffer;
-
-	for (i = y; i < y + height ; i++) {
-		const int line_offset = dev->info->fix.line_length * i;
-		const int byte_offset = line_offset + (x * BPP);
-
-		if (dlfb_render_hline(dev, &urb,
-				      (char *) dev->info->fix.smem_start,
-				      &cmd, byte_offset, width * BPP,
-				      &bytes_identical, &bytes_sent))
-			goto error;
-	}
-
-	if (cmd > (char *) urb->transfer_buffer) {
-		/* Send partial buffer remaining before exiting */
-		int len = cmd - (char *) urb->transfer_buffer;
-		ret = dlfb_submit_urb(dev, urb, len);
-		bytes_sent += len;
-	} else
-		dlfb_urb_completion(urb);
-
-error:
-	atomic_add(bytes_sent, &dev->bytes_sent);
-	atomic_add(bytes_identical, &dev->bytes_identical);
-	atomic_add(width*height*2, &dev->bytes_rendered);
-	end_cycles = get_cycles();
-	atomic_add(((unsigned int) ((end_cycles - start_cycles)
-		    >> 10)), /* Kcycles */
-		   &dev->cpu_kcycles_used);
-
-	return 0;
-}
-
-static ssize_t dlfb_ops_read(struct fb_info *info, char __user *buf,
-			 size_t count, loff_t *ppos)
-{
-	ssize_t result = -ENOSYS;
-
-#if defined CONFIG_FB_SYS_FOPS || defined CONFIG_FB_SYS_FOPS_MODULE
-	result = fb_sys_read(info, buf, count, ppos);
-#endif
-
-	return result;
-}
-
-/*
- * Path triggered by usermode clients who write to filesystem
- * e.g. cat filename > /dev/fb1
- * Not used by X Windows or text-mode console. But useful for testing.
- * Slow because of extra copy and we must assume all pixels dirty.
- */
-static ssize_t dlfb_ops_write(struct fb_info *info, const char __user *buf,
-			  size_t count, loff_t *ppos)
-{
-	ssize_t result = -ENOSYS;
-	struct dlfb_data *dev = info->par;
-	u32 offset = (u32) *ppos;
-
-#if defined CONFIG_FB_SYS_FOPS || defined CONFIG_FB_SYS_FOPS_MODULE
-
-	result = fb_sys_write(info, buf, count, ppos);
-
-	if (result > 0) {
-		int start = max((int)(offset / info->fix.line_length) - 1, 0);
-		int lines = min((u32)((result / info->fix.line_length) + 1),
-				(u32)info->var.yres);
-
-		dlfb_handle_damage(dev, 0, start, info->var.xres,
-			lines, info->screen_base);
-	}
-#endif
-
-	return result;
-}
-
-/* hardware has native COPY command (see libdlo), but not worth it for fbcon */
-static void dlfb_ops_copyarea(struct fb_info *info,
-				const struct fb_copyarea *area)
-{
-
-	struct dlfb_data *dev = info->par;
-
-#if defined CONFIG_FB_SYS_COPYAREA || defined CONFIG_FB_SYS_COPYAREA_MODULE
-
-	sys_copyarea(info, area);
-
-	dlfb_handle_damage(dev, area->dx, area->dy,
-			area->width, area->height, info->screen_base);
-#endif
-
-}
-
-static void dlfb_ops_imageblit(struct fb_info *info,
-				const struct fb_image *image)
-{
-	struct dlfb_data *dev = info->par;
-
-#if defined CONFIG_FB_SYS_IMAGEBLIT || defined CONFIG_FB_SYS_IMAGEBLIT_MODULE
-
-	sys_imageblit(info, image);
-
-	dlfb_handle_damage(dev, image->dx, image->dy,
-			image->width, image->height, info->screen_base);
-
-#endif
-
-}
-
-static void dlfb_ops_fillrect(struct fb_info *info,
-			  const struct fb_fillrect *rect)
-{
-	struct dlfb_data *dev = info->par;
-
-#if defined CONFIG_FB_SYS_FILLRECT || defined CONFIG_FB_SYS_FILLRECT_MODULE
-
-	sys_fillrect(info, rect);
-
-	dlfb_handle_damage(dev, rect->dx, rect->dy, rect->width,
-			      rect->height, info->screen_base);
-#endif
-
-}
-
-#ifdef CONFIG_FB_DEFERRED_IO
-/*
- * NOTE: fb_defio.c is holding info->fbdefio.mutex
- *   Touching ANY framebuffer memory that triggers a page fault
- *   in fb_defio will cause a deadlock, when it also tries to
- *   grab the same mutex.
- */
-static void dlfb_dpy_deferred_io(struct fb_info *info,
-				struct list_head *pagelist)
-{
-	struct page *cur;
-	struct fb_deferred_io *fbdefio = info->fbdefio;
-	struct dlfb_data *dev = info->par;
-	struct urb *urb;
-	char *cmd;
-	cycles_t start_cycles, end_cycles;
-	int bytes_sent = 0;
-	int bytes_identical = 0;
-	int bytes_rendered = 0;
-
-	if (!fb_defio)
-		return;
-
-	if (!atomic_read(&dev->usb_active))
-		return;
-
-	start_cycles = get_cycles();
-
-	urb = dlfb_get_urb(dev);
-	if (!urb)
-		return;
-
-	cmd = urb->transfer_buffer;
-
-	/* walk the written page list and render each to device */
-	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
-
-		if (dlfb_render_hline(dev, &urb, (char *) info->fix.smem_start,
-				  &cmd, cur->index << PAGE_SHIFT,
-				  PAGE_SIZE, &bytes_identical, &bytes_sent))
-			goto error;
-		bytes_rendered += PAGE_SIZE;
-	}
-
-	if (cmd > (char *) urb->transfer_buffer) {
-		/* Send partial buffer remaining before exiting */
-		int len = cmd - (char *) urb->transfer_buffer;
-		dlfb_submit_urb(dev, urb, len);
-		bytes_sent += len;
-	} else
-		dlfb_urb_completion(urb);
-
-error:
-	atomic_add(bytes_sent, &dev->bytes_sent);
-	atomic_add(bytes_identical, &dev->bytes_identical);
-	atomic_add(bytes_rendered, &dev->bytes_rendered);
-	end_cycles = get_cycles();
-	atomic_add(((unsigned int) ((end_cycles - start_cycles)
-		    >> 10)), /* Kcycles */
-		   &dev->cpu_kcycles_used);
-}
-
-#endif
-
-static int dlfb_get_edid(struct dlfb_data *dev, char *edid, int len)
-{
-	int i;
-	int ret;
-	char *rbuf;
-
-	rbuf = kmalloc(2, GFP_KERNEL);
-	if (!rbuf)
-		return 0;
-
-	for (i = 0; i < len; i++) {
-		ret = usb_control_msg(dev->udev,
-				    usb_rcvctrlpipe(dev->udev, 0), (0x02),
-				    (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
-				    HZ);
-		if (ret < 1) {
-			dl_err("Read EDID byte %d failed err %x\n", i, ret);
-			i--;
-			break;
-		}
-		edid[i] = rbuf[1];
-	}
-
-	kfree(rbuf);
-
-	return i;
-}
-
-static int dlfb_ops_ioctl(struct fb_info *info, unsigned int cmd,
-				unsigned long arg)
-{
-
-	struct dlfb_data *dev = info->par;
-	struct dloarea *area = NULL;
-
-	if (!atomic_read(&dev->usb_active))
-		return 0;
-
-	/* TODO: Update X server to get this from sysfs instead */
-	if (cmd == DLFB_IOCTL_RETURN_EDID) {
-		char *edid = (char *)arg;
-		if (copy_to_user(edid, dev->edid, dev->edid_size))
-			return -EFAULT;
-		return 0;
-	}
-
-	/* TODO: Help propose a standard fb.h ioctl to report mmap damage */
-	if (cmd == DLFB_IOCTL_REPORT_DAMAGE) {
-
-		/*
-		 * If we have a damage-aware client, turn fb_defio "off"
-		 * To avoid perf imact of unecessary page fault handling.
-		 * Done by resetting the delay for this fb_info to a very
-		 * long period. Pages will become writable and stay that way.
-		 * Reset to normal value when all clients have closed this fb.
-		 */
-		if (info->fbdefio)
-			info->fbdefio->delay = DL_DEFIO_WRITE_DISABLE;
-
-		area = (struct dloarea *)arg;
-
-		if (area->x < 0)
-			area->x = 0;
-
-		if (area->x > info->var.xres)
-			area->x = info->var.xres;
-
-		if (area->y < 0)
-			area->y = 0;
-
-		if (area->y > info->var.yres)
-			area->y = info->var.yres;
-
-		dlfb_handle_damage(dev, area->x, area->y, area->w, area->h,
-			   info->screen_base);
-	}
-
-	return 0;
-}
-
-/* taken from vesafb */
-static int
-dlfb_ops_setcolreg(unsigned regno, unsigned red, unsigned green,
-	       unsigned blue, unsigned transp, struct fb_info *info)
-{
-	int err = 0;
-
-	if (regno >= info->cmap.len)
-		return 1;
-
-	if (regno < 16) {
-		if (info->var.red.offset == 10) {
-			/* 1:5:5:5 */
-			((u32 *) (info->pseudo_palette))[regno] =
-			    ((red & 0xf800) >> 1) |
-			    ((green & 0xf800) >> 6) | ((blue & 0xf800) >> 11);
-		} else {
-			/* 0:5:6:5 */
-			((u32 *) (info->pseudo_palette))[regno] =
-			    ((red & 0xf800)) |
-			    ((green & 0xfc00) >> 5) | ((blue & 0xf800) >> 11);
-		}
-	}
-
-	return err;
-}
-
-/*
- * It's common for several clients to have framebuffer open simultaneously.
- * e.g. both fbcon and X. Makes things interesting.
- * Assumes caller is holding info->lock (for open and release at least)
- */
-static int dlfb_ops_open(struct fb_info *info, int user)
-{
-	struct dlfb_data *dev = info->par;
-
-	/*
-	 * fbcon aggressively connects to first framebuffer it finds,
-	 * preventing other clients (X) from working properly. Usually
-	 * not what the user wants. Fail by default with option to enable.
-	 */
-	if ((user == 0) & (!console))
-		return -EBUSY;
-
-	/* If the USB device is gone, we don't accept new opens */
-	if (dev->virtualized)
-		return -ENODEV;
-
-	dev->fb_count++;
-
-	kref_get(&dev->kref);
-
-#ifdef CONFIG_FB_DEFERRED_IO
-	if (fb_defio && (info->fbdefio == NULL)) {
-		/* enable defio at last moment if not disabled by client */
-
-		struct fb_deferred_io *fbdefio;
-
-		fbdefio = kmalloc(sizeof(struct fb_deferred_io), GFP_KERNEL);
-
-		if (fbdefio) {
-			fbdefio->delay = DL_DEFIO_WRITE_DELAY;
-			fbdefio->deferred_io = dlfb_dpy_deferred_io;
-		}
-
-		info->fbdefio = fbdefio;
-		fb_deferred_io_init(info);
-	}
-#endif
-
-	dl_notice("open /dev/fb%d user=%d fb_info=%p count=%d\n",
-	    info->node, user, info, dev->fb_count);
-
-	return 0;
-}
-
-/*
- * Called when all client interfaces to start transactions have been disabled,
- * and all references to our device instance (dlfb_data) are released.
- * Every transaction must have a reference, so we know are fully spun down
- */
-static void dlfb_free(struct kref *kref)
-{
-	struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);
-
-	/* this function will wait for all in-flight urbs to complete */
-	if (dev->urbs.count > 0)
-		dlfb_free_urb_list(dev);
-
-	if (dev->backing_buffer)
-		vfree(dev->backing_buffer);
-
-	kfree(dev->edid);
-
-	dl_warn("freeing dlfb_data %p\n", dev);
-
-	kfree(dev);
-}
-
-static void dlfb_release_urb_work(struct work_struct *work)
-{
-	struct urb_node *unode = container_of(work, struct urb_node,
-					      release_urb_work.work);
-
-	up(&unode->dev->urbs.limit_sem);
-}
-
-static void dlfb_free_framebuffer_work(struct work_struct *work)
-{
-	struct dlfb_data *dev = container_of(work, struct dlfb_data,
-					     free_framebuffer_work.work);
-	struct fb_info *info = dev->info;
-	int node = info->node;
-
-	unregister_framebuffer(info);
-
-	if (info->cmap.len != 0)
-		fb_dealloc_cmap(&info->cmap);
-	if (info->monspecs.modedb)
-		fb_destroy_modedb(info->monspecs.modedb);
-	if (info->screen_base)
-		vfree(info->screen_base);
-
-	fb_destroy_modelist(&info->modelist);
-
-	dev->info = 0;
-
-	/* Assume info structure is freed after this point */
-	framebuffer_release(info);
-
-	dl_warn("fb_info for /dev/fb%d has been freed\n", node);
-
-	/* ref taken in probe() as part of registering framebfufer */
-	kref_put(&dev->kref, dlfb_free);
-}
-
-/*
- * Assumes caller is holding info->lock mutex (for open and release at least)
- */
-static int dlfb_ops_release(struct fb_info *info, int user)
-{
-	struct dlfb_data *dev = info->par;
-
-	dev->fb_count--;
-
-	/* We can't free fb_info here - fbmem will touch it when we return */
-	if (dev->virtualized && (dev->fb_count == 0))
-		schedule_delayed_work(&dev->free_framebuffer_work, HZ);
-
-#ifdef CONFIG_FB_DEFERRED_IO
-	if ((dev->fb_count == 0) && (info->fbdefio)) {
-		fb_deferred_io_cleanup(info);
-		kfree(info->fbdefio);
-		info->fbdefio = NULL;
-		info->fbops->fb_mmap = dlfb_ops_mmap;
-	}
-#endif
-
-	dl_warn("released /dev/fb%d user=%d count=%d\n",
-		  info->node, user, dev->fb_count);
-
-	kref_put(&dev->kref, dlfb_free);
-
-	return 0;
-}
-
-/*
- * Check whether a video mode is supported by the DisplayLink chip
- * We start from monitor's modes, so don't need to filter that here
- */
-static int dlfb_is_valid_mode(struct fb_videomode *mode,
-		struct fb_info *info)
-{
-	struct dlfb_data *dev = info->par;
-
-	if (mode->xres * mode->yres > dev->sku_pixel_limit) {
-		dl_warn("%dx%d beyond chip capabilities\n",
-		       mode->xres, mode->yres);
-		return 0;
-	}
-
-	dl_info("%dx%d valid mode\n", mode->xres, mode->yres);
-
-	return 1;
-}
-
-static void dlfb_var_color_format(struct fb_var_screeninfo *var)
-{
-	const struct fb_bitfield red = { 11, 5, 0 };
-	const struct fb_bitfield green = { 5, 6, 0 };
-	const struct fb_bitfield blue = { 0, 5, 0 };
-
-	var->bits_per_pixel = 16;
-	var->red = red;
-	var->green = green;
-	var->blue = blue;
-}
-
-static int dlfb_ops_check_var(struct fb_var_screeninfo *var,
-				struct fb_info *info)
-{
-	struct fb_videomode mode;
-
-	/* TODO: support dynamically changing framebuffer size */
-	if ((var->xres * var->yres * 2) > info->fix.smem_len)
-		return -EINVAL;
-
-	/* set device-specific elements of var unrelated to mode */
-	dlfb_var_color_format(var);
-
-	fb_var_to_videomode(&mode, var);
-
-	if (!dlfb_is_valid_mode(&mode, info))
-		return -EINVAL;
-
-	return 0;
-}
-
-static int dlfb_ops_set_par(struct fb_info *info)
-{
-	struct dlfb_data *dev = info->par;
-	int result;
-	u16 *pix_framebuffer;
-	int i;
-
-	dl_notice("set_par mode %dx%d\n", info->var.xres, info->var.yres);
-
-	result = dlfb_set_video_mode(dev, &info->var);
-
-	if ((result == 0) && (dev->fb_count == 0)) {
-
-		/* paint greenscreen */
-
-		pix_framebuffer = (u16 *) info->screen_base;
-		for (i = 0; i < info->fix.smem_len / 2; i++)
-			pix_framebuffer[i] = 0x37e6;
-
-		dlfb_handle_damage(dev, 0, 0, info->var.xres, info->var.yres,
-				   info->screen_base);
-	}
-
-	return result;
-}
-
-/*
- * In order to come back from full DPMS off, we need to set the mode again
- */
-static int dlfb_ops_blank(int blank_mode, struct fb_info *info)
-{
-	struct dlfb_data *dev = info->par;
-
-	if (blank_mode != FB_BLANK_UNBLANK) {
-		char *bufptr;
-		struct urb *urb;
-
-		urb = dlfb_get_urb(dev);
-		if (!urb)
-			return 0;
-
-		bufptr = (char *) urb->transfer_buffer;
-		bufptr = dlfb_vidreg_lock(bufptr);
-		bufptr = dlfb_enable_hvsync(bufptr, false);
-		bufptr = dlfb_vidreg_unlock(bufptr);
-
-		dlfb_submit_urb(dev, urb, bufptr -
-				(char *) urb->transfer_buffer);
-	} else {
-		dlfb_set_video_mode(dev, &info->var);
-	}
-
-	return 0;
-}
-
-static struct fb_ops dlfb_ops = {
-	.owner = THIS_MODULE,
-	.fb_read = dlfb_ops_read,
-	.fb_write = dlfb_ops_write,
-	.fb_setcolreg = dlfb_ops_setcolreg,
-	.fb_fillrect = dlfb_ops_fillrect,
-	.fb_copyarea = dlfb_ops_copyarea,
-	.fb_imageblit = dlfb_ops_imageblit,
-	.fb_mmap = dlfb_ops_mmap,
-	.fb_ioctl = dlfb_ops_ioctl,
-	.fb_open = dlfb_ops_open,
-	.fb_release = dlfb_ops_release,
-	.fb_blank = dlfb_ops_blank,
-	.fb_check_var = dlfb_ops_check_var,
-	.fb_set_par = dlfb_ops_set_par,
-};
-
-
-/*
- * Assumes &info->lock held by caller
- * Assumes no active clients have framebuffer open
- */
-static int dlfb_realloc_framebuffer(struct dlfb_data *dev, struct fb_info *info)
-{
-	int retval = -ENOMEM;
-	int old_len = info->fix.smem_len;
-	int new_len;
-	unsigned char *old_fb = info->screen_base;
-	unsigned char *new_fb;
-	unsigned char *new_back;
-
-	dl_warn("Reallocating framebuffer. Addresses will change!\n");
-
-	new_len = info->fix.line_length * info->var.yres;
-
-	if (PAGE_ALIGN(new_len) > old_len) {
-		/*
-		 * Alloc system memory for virtual framebuffer
-		 */
-		new_fb = vmalloc(new_len);
-		if (!new_fb) {
-			dl_err("Virtual framebuffer alloc failed\n");
-			goto error;
-		}
-
-		if (info->screen_base) {
-			memcpy(new_fb, old_fb, old_len);
-			vfree(info->screen_base);
-		}
-
-		info->screen_base = new_fb;
-		info->fix.smem_len = PAGE_ALIGN(new_len);
-		info->fix.smem_start = (unsigned long) new_fb;
-		info->flags = udlfb_info_flags;
-
-		/*
-		 * Second framebuffer copy to mirror the framebuffer state
-		 * on the physical USB device. We can function without this.
-		 * But with imperfect damage info we may send pixels over USB
-		 * that were, in fact, unchanged - wasting limited USB bandwidth
-		 */
-		new_back = vmalloc(new_len);
-		if (!new_back)
-			dl_info("No shadow/backing buffer allcoated\n");
-		else {
-			if (dev->backing_buffer)
-				vfree(dev->backing_buffer);
-			dev->backing_buffer = new_back;
-			memset(dev->backing_buffer, 0, new_len);
-		}
-	}
-
-	retval = 0;
-
-error:
-	return retval;
-}
-
-/*
- * 1) Get EDID from hw, or use sw default
- * 2) Parse into various fb_info structs
- * 3) Allocate virtual framebuffer memory to back highest res mode
- *
- * Parses EDID into three places used by various parts of fbdev:
- * fb_var_screeninfo contains the timing of the monitor's preferred mode
- * fb_info.monspecs is full parsed EDID info, including monspecs.modedb
- * fb_info.modelist is a linked list of all monitor & VESA modes which work
- *
- * If EDID is not readable/valid, then modelist is all VESA modes,
- * monspecs is NULL, and fb_var_screeninfo is set to safe VESA mode
- * Returns 0 if successful
- */
-static int dlfb_setup_modes(struct dlfb_data *dev,
-			   struct fb_info *info,
-			   char *default_edid, size_t default_edid_size)
-{
-	int i;
-	const struct fb_videomode *default_vmode = NULL;
-	int result = 0;
-	char *edid;
-	int tries = 3;
-
-	if (info->dev) /* only use mutex if info has been registered */
-		mutex_lock(&info->lock);
-
-	edid = kmalloc(MAX_EDID_SIZE, GFP_KERNEL);
-	if (!edid) {
-		result = -ENOMEM;
-		goto error;
-	}
-
-	fb_destroy_modelist(&info->modelist);
-	memset(&info->monspecs, 0, sizeof(info->monspecs));
-
-	/*
-	 * Try to (re)read EDID from hardware first
-	 * EDID data may return, but not parse as valid
-	 * Try again a few times, in case of e.g. analog cable noise
-	 */
-	while (tries--) {
-
-		i = dlfb_get_edid(dev, edid, MAX_EDID_SIZE);
-
-		if (i >= MIN_EDID_SIZE)
-			fb_edid_to_monspecs(edid, &info->monspecs);
-
-		if (info->monspecs.modedb_len > 0) {
-			dev->edid = edid;
-			dev->edid_size = i;
-			break;
-		}
-	}
-
-	/* If that fails, use a previously returned EDID if available */
-	if (info->monspecs.modedb_len == 0) {
-
-		dl_err("Unable to get valid EDID from device/display\n");
-
-		if (dev->edid) {
-			fb_edid_to_monspecs(dev->edid, &info->monspecs);
-			if (info->monspecs.modedb_len > 0)
-				dl_err("Using previously queried EDID\n");
-		}
-	}
-
-	/* If that fails, use the default EDID we were handed */
-	if (info->monspecs.modedb_len == 0) {
-		if (default_edid_size >= MIN_EDID_SIZE) {
-			fb_edid_to_monspecs(default_edid, &info->monspecs);
-			if (info->monspecs.modedb_len > 0) {
-				memcpy(edid, default_edid, default_edid_size);
-				dev->edid = edid;
-				dev->edid_size = default_edid_size;
-				dl_err("Using default/backup EDID\n");
-			}
-		}
-	}
-
-	/* If we've got modes, let's pick a best default mode */
-	if (info->monspecs.modedb_len > 0) {
-
-		for (i = 0; i < info->monspecs.modedb_len; i++) {
-			if (dlfb_is_valid_mode(&info->monspecs.modedb[i], info))
-				fb_add_videomode(&info->monspecs.modedb[i],
-					&info->modelist);
-			else /* if we've removed top/best mode */
-				info->monspecs.misc &= ~FB_MISC_1ST_DETAIL;
-		}
-
-		default_vmode = fb_find_best_display(&info->monspecs,
-						     &info->modelist);
-	}
-
-	/* If everything else has failed, fall back to safe default mode */
-	if (default_vmode == NULL) {
-
-		struct fb_videomode fb_vmode = {0};
-
-		/*
-		 * Add the standard VESA modes to our modelist
-		 * Since we don't have EDID, there may be modes that
-		 * overspec monitor and/or are incorrect aspect ratio, etc.
-		 * But at least the user has a chance to choose
-		 */
-		for (i = 0; i < VESA_MODEDB_SIZE; i++) {
-			if (dlfb_is_valid_mode((struct fb_videomode *)
-						&vesa_modes[i], info))
-				fb_add_videomode(&vesa_modes[i],
-						 &info->modelist);
-		}
-
-		/*
-		 * default to resolution safe for projectors
-		 * (since they are most common case without EDID)
-		 */
-		fb_vmode.xres = 800;
-		fb_vmode.yres = 600;
-		fb_vmode.refresh = 60;
-		default_vmode = fb_find_nearest_mode(&fb_vmode,
-						     &info->modelist);
-	}
-
-	/* If we have good mode and no active clients*/
-	if ((default_vmode != NULL) && (dev->fb_count == 0)) {
-
-		fb_videomode_to_var(&info->var, default_vmode);
-		dlfb_var_color_format(&info->var);
-
-		/*
-		 * with mode size info, we can now alloc our framebuffer.
-		 */
-		memcpy(&info->fix, &dlfb_fix, sizeof(dlfb_fix));
-		info->fix.line_length = info->var.xres *
-			(info->var.bits_per_pixel / 8);
-
-		result = dlfb_realloc_framebuffer(dev, info);
-
-	} else
-		result = -EINVAL;
-
-error:
-	if (edid && (dev->edid != edid))
-		kfree(edid);
-
-	if (info->dev)
-		mutex_unlock(&info->lock);
-
-	return result;
-}
-
-static ssize_t metrics_bytes_rendered_show(struct device *fbdev,
-				   struct device_attribute *a, char *buf) {
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			atomic_read(&dev->bytes_rendered));
-}
-
-static ssize_t metrics_bytes_identical_show(struct device *fbdev,
-				   struct device_attribute *a, char *buf) {
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			atomic_read(&dev->bytes_identical));
-}
-
-static ssize_t metrics_bytes_sent_show(struct device *fbdev,
-				   struct device_attribute *a, char *buf) {
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			atomic_read(&dev->bytes_sent));
-}
-
-static ssize_t metrics_cpu_kcycles_used_show(struct device *fbdev,
-				   struct device_attribute *a, char *buf) {
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			atomic_read(&dev->cpu_kcycles_used));
-}
-
-static ssize_t edid_show(
-			struct file *filp,
-			struct kobject *kobj, struct bin_attribute *a,
-			 char *buf, loff_t off, size_t count) {
-	struct device *fbdev = container_of(kobj, struct device, kobj);
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-
-	if (dev->edid == NULL)
-		return 0;
-
-	if ((off >= dev->edid_size) || (count > dev->edid_size))
-		return 0;
-
-	if (off + count > dev->edid_size)
-		count = dev->edid_size - off;
-
-	dl_info("sysfs edid copy %p to %p, %d bytes\n",
-		dev->edid, buf, (int) count);
-
-	memcpy(buf, dev->edid, count);
-
-	return count;
-}
-
-static ssize_t edid_store(
-			struct file *filp,
-			struct kobject *kobj, struct bin_attribute *a,
-			char *src, loff_t src_off, size_t src_size) {
-	struct device *fbdev = container_of(kobj, struct device, kobj);
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-
-	/* We only support write of entire EDID at once, no offset*/
-	if ((src_size < MIN_EDID_SIZE) ||
-	    (src_size > MAX_EDID_SIZE) ||
-	    (src_off != 0))
-		return 0;
-
-	dlfb_setup_modes(dev, fb_info, src, src_size);
-
-	if (dev->edid && (memcmp(src, dev->edid, src_size) == 0)) {
-		dl_info("sysfs written EDID is new default\n");
-		dlfb_ops_set_par(fb_info);
-		return src_size;
-	} else
-		return 0;
-}
-
-static ssize_t metrics_reset_store(struct device *fbdev,
-			   struct device_attribute *attr,
-			   const char *buf, size_t count)
-{
-	struct fb_info *fb_info = dev_get_drvdata(fbdev);
-	struct dlfb_data *dev = fb_info->par;
-
-	atomic_set(&dev->bytes_rendered, 0);
-	atomic_set(&dev->bytes_identical, 0);
-	atomic_set(&dev->bytes_sent, 0);
-	atomic_set(&dev->cpu_kcycles_used, 0);
-
-	return count;
-}
-
-static struct bin_attribute edid_attr = {
-	.attr.name = "edid",
-	.attr.mode = 0666,
-	.size = MAX_EDID_SIZE,
-	.read = edid_show,
-	.write = edid_store
-};
-
-static struct device_attribute fb_device_attrs[] = {
-	__ATTR_RO(metrics_bytes_rendered),
-	__ATTR_RO(metrics_bytes_identical),
-	__ATTR_RO(metrics_bytes_sent),
-	__ATTR_RO(metrics_cpu_kcycles_used),
-	__ATTR(metrics_reset, S_IWUGO, NULL, metrics_reset_store),
-};
-
-/*
- * This is necessary before we can communicate with the display controller.
- */
-static int dlfb_select_std_channel(struct dlfb_data *dev)
-{
-	int ret;
-	u8 set_def_chn[] = {	   0x57, 0xCD, 0xDC, 0xA7,
-				0x1C, 0x88, 0x5E, 0x15,
-				0x60, 0xFE, 0xC6, 0x97,
-				0x16, 0x3D, 0x47, 0xF2  };
-
-	ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
-			NR_USB_REQUEST_CHANNEL,
-			(USB_DIR_OUT | USB_TYPE_VENDOR), 0, 0,
-			set_def_chn, sizeof(set_def_chn), USB_CTRL_SET_TIMEOUT);
-	return ret;
-}
-
-static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
-					struct usb_device *usbdev)
-{
-	char *desc;
-	char *buf;
-	char *desc_end;
-
-	u8 total_len = 0;
-
-	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
-	if (!buf)
-		return false;
-	desc = buf;
-
-	total_len = usb_get_descriptor(usbdev, 0x5f, /* vendor specific */
-				    0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
-	if (total_len > 5) {
-		dl_info("vendor descriptor length:%x data:%02x %02x %02x %02x" \
-			"%02x %02x %02x %02x %02x %02x %02x\n",
-			total_len, desc[0],
-			desc[1], desc[2], desc[3], desc[4], desc[5], desc[6],
-			desc[7], desc[8], desc[9], desc[10]);
-
-		if ((desc[0] != total_len) || /* descriptor length */
-		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
-		    (desc[2] != 0x01) ||   /* version (2 bytes) */
-		    (desc[3] != 0x00) ||
-		    (desc[4] != total_len - 2)) /* length after type */
-			goto unrecognized;
-
-		desc_end = desc + total_len;
-		desc += 5; /* the fixed header we've already parsed */
-
-		while (desc < desc_end) {
-			u8 length;
-			u16 key;
-
-			key = *((u16 *) desc);
-			desc += sizeof(u16);
-			length = *desc;
-			desc++;
-
-			switch (key) {
-			case 0x0200: { /* max_area */
-				u32 max_area;
-				max_area = le32_to_cpu(*((u32 *)desc));
-				dl_warn("DL chip limited to %d pixel modes\n",
-					max_area);
-				dev->sku_pixel_limit = max_area;
-				break;
-			}
-			default:
-				break;
-			}
-			desc += length;
-		}
-	}
-
-	goto success;
-
-unrecognized:
-	/* allow udlfb to load for now even if firmware unrecognized */
-	dl_err("Unrecognized vendor firmware descriptor\n");
-
-success:
-	kfree(buf);
-	return true;
-}
-static int dlfb_usb_probe(struct usb_interface *interface,
-			const struct usb_device_id *id)
-{
-	struct usb_device *usbdev;
-	struct dlfb_data *dev = 0;
-	struct fb_info *info = 0;
-	int retval = -ENOMEM;
-	int i;
-
-	/* usb initialization */
-
-	usbdev = interface_to_usbdev(interface);
-
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-	if (dev == NULL) {
-		err("dlfb_usb_probe: failed alloc of dev struct\n");
-		goto error;
-	}
-
-	/* we need to wait for both usb and fbdev to spin down on disconnect */
-	kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */
-	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */
-
-	dev->udev = usbdev;
-	dev->gdev = &usbdev->dev; /* our generic struct device * */
-	usb_set_intfdata(interface, dev);
-
-	dl_info("%s %s - serial #%s\n",
-		usbdev->manufacturer, usbdev->product, usbdev->serial);
-	dl_info("vid_%04x&pid_%04x&rev_%04x driver's dlfb_data struct at %p\n",
-		usbdev->descriptor.idVendor, usbdev->descriptor.idProduct,
-		usbdev->descriptor.bcdDevice, dev);
-	dl_info("console enable=%d\n", console);
-	dl_info("fb_defio enable=%d\n", fb_defio);
-
-	dev->sku_pixel_limit = 2048 * 1152; /* default to maximum */
-
-	if (!dlfb_parse_vendor_descriptor(dev, usbdev)) {
-		dl_err("firmware not recognized. Assume incompatible device\n");
-		goto error;
-	}
-
-	if (!dlfb_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
-		retval = -ENOMEM;
-		dl_err("dlfb_alloc_urb_list failed\n");
-		goto error;
-	}
-
-	/* We don't register a new USB class. Our client interface is fbdev */
-
-	/* allocates framebuffer driver structure, not framebuffer memory */
-	info = framebuffer_alloc(0, &usbdev->dev);
-	if (!info) {
-		retval = -ENOMEM;
-		dl_err("framebuffer_alloc failed\n");
-		goto error;
-	}
-
-	dev->info = info;
-	info->par = dev;
-	info->pseudo_palette = dev->pseudo_palette;
-	info->fbops = &dlfb_ops;
-
-	retval = fb_alloc_cmap(&info->cmap, 256, 0);
-	if (retval < 0) {
-		dl_err("fb_alloc_cmap failed %x\n", retval);
-		goto error;
-	}
-
-	INIT_DELAYED_WORK(&dev->free_framebuffer_work,
-			  dlfb_free_framebuffer_work);
-
-	INIT_LIST_HEAD(&info->modelist);
-
-	retval = dlfb_setup_modes(dev, info, NULL, 0);
-	if (retval != 0) {
-		dl_err("unable to find common mode for display and adapter\n");
-		goto error;
-	}
-
-	/* ready to begin using device */
-
-	atomic_set(&dev->usb_active, 1);
-	dlfb_select_std_channel(dev);
-
-	dlfb_ops_check_var(&info->var, info);
-	dlfb_ops_set_par(info);
-
-	retval = register_framebuffer(info);
-	if (retval < 0) {
-		dl_err("register_framebuffer failed %d\n", retval);
-		goto error;
-	}
-
-	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
-		device_create_file(info->dev, &fb_device_attrs[i]);
-
-	device_create_bin_file(info->dev, &edid_attr);
-
-	dl_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."
-			" Using %dK framebuffer memory\n", info->node,
-			info->var.xres, info->var.yres,
-			((dev->backing_buffer) ?
-			info->fix.smem_len * 2 : info->fix.smem_len) >> 10);
-	return 0;
-
-error:
-	if (dev) {
-
-		if (info) {
-			if (info->cmap.len != 0)
-				fb_dealloc_cmap(&info->cmap);
-			if (info->monspecs.modedb)
-				fb_destroy_modedb(info->monspecs.modedb);
-			if (info->screen_base)
-				vfree(info->screen_base);
-
-			fb_destroy_modelist(&info->modelist);
-
-			framebuffer_release(info);
-		}
-
-		if (dev->backing_buffer)
-			vfree(dev->backing_buffer);
-
-		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
-		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */
-
-		/* dev has been deallocated. Do not dereference */
-	}
-
-	return retval;
-}
-
-static void dlfb_usb_disconnect(struct usb_interface *interface)
-{
-	struct dlfb_data *dev;
-	struct fb_info *info;
-	int i;
-
-	dev = usb_get_intfdata(interface);
-	info = dev->info;
-
-	dl_info("USB disconnect starting\n");
-
-	/* we virtualize until all fb clients release. Then we free */
-	dev->virtualized = true;
-
-	/* When non-active we'll update virtual framebuffer, but no new urbs */
-	atomic_set(&dev->usb_active, 0);
-
-	/* remove udlfb's sysfs interfaces */
-	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
-		device_remove_file(info->dev, &fb_device_attrs[i]);
-	device_remove_bin_file(info->dev, &edid_attr);
-
-	usb_set_intfdata(interface, NULL);
-
-	/* if clients still have us open, will be freed on last close */
-	if (dev->fb_count == 0)
-		schedule_delayed_work(&dev->free_framebuffer_work, 0);
-
-	/* release reference taken by kref_init in probe() */
-	kref_put(&dev->kref, dlfb_free);
-
-	/* consider dlfb_data freed */
-
-	return;
-}
-
-static struct usb_driver dlfb_driver = {
-	.name = "udlfb",
-	.probe = dlfb_usb_probe,
-	.disconnect = dlfb_usb_disconnect,
-	.id_table = id_table,
-};
-
-static int __init dlfb_module_init(void)
-{
-	int res;
-
-	res = usb_register(&dlfb_driver);
-	if (res)
-		err("usb_register failed. Error number %d", res);
-
-	return res;
-}
-
-static void __exit dlfb_module_exit(void)
-{
-	usb_deregister(&dlfb_driver);
-}
-
-module_init(dlfb_module_init);
-module_exit(dlfb_module_exit);
-
-static void dlfb_urb_completion(struct urb *urb)
-{
-	struct urb_node *unode = urb->context;
-	struct dlfb_data *dev = unode->dev;
-	unsigned long flags;
-
-	/* sync/async unlink faults aren't errors */
-	if (urb->status) {
-		if (!(urb->status == -ENOENT ||
-		    urb->status == -ECONNRESET ||
-		    urb->status == -ESHUTDOWN)) {
-			dl_err("%s - nonzero write bulk status received: %d\n",
-				__func__, urb->status);
-			atomic_set(&dev->lost_pixels, 1);
-		}
-	}
-
-	urb->transfer_buffer_length = dev->urbs.size; /* reset to actual */
-
-	spin_lock_irqsave(&dev->urbs.lock, flags);
-	list_add_tail(&unode->entry, &dev->urbs.list);
-	dev->urbs.available++;
-	spin_unlock_irqrestore(&dev->urbs.lock, flags);
-
-	/*
-	 * When using fb_defio, we deadlock if up() is called
-	 * while another is waiting. So queue to another process.
-	 */
-	if (fb_defio)
-		schedule_delayed_work(&unode->release_urb_work, 0);
-	else
-		up(&dev->urbs.limit_sem);
-}
-
-static void dlfb_free_urb_list(struct dlfb_data *dev)
-{
-	int count = dev->urbs.count;
-	struct list_head *node;
-	struct urb_node *unode;
-	struct urb *urb;
-	int ret;
-	unsigned long flags;
-
-	dl_notice("Waiting for completes and freeing all render urbs\n");
-
-	/* keep waiting and freeing, until we've got 'em all */
-	while (count--) {
-
-		/* Getting interrupted means a leak, but ok at shutdown*/
-		ret = down_interruptible(&dev->urbs.limit_sem);
-		if (ret)
-			break;
-
-		spin_lock_irqsave(&dev->urbs.lock, flags);
-
-		node = dev->urbs.list.next; /* have reserved one with sem */
-		list_del_init(node);
-
-		spin_unlock_irqrestore(&dev->urbs.lock, flags);
-
-		unode = list_entry(node, struct urb_node, entry);
-		urb = unode->urb;
-
-		/* Free each separately allocated piece */
-		usb_free_coherent(urb->dev, dev->urbs.size,
-				  urb->transfer_buffer, urb->transfer_dma);
-		usb_free_urb(urb);
-		kfree(node);
-	}
-
-}
-
-static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
-{
-	int i = 0;
-	struct urb *urb;
-	struct urb_node *unode;
-	char *buf;
-
-	spin_lock_init(&dev->urbs.lock);
-
-	dev->urbs.size = size;
-	INIT_LIST_HEAD(&dev->urbs.list);
-
-	while (i < count) {
-		unode = kzalloc(sizeof(struct urb_node), GFP_KERNEL);
-		if (!unode)
-			break;
-		unode->dev = dev;
-
-		INIT_DELAYED_WORK(&unode->release_urb_work,
-			  dlfb_release_urb_work);
-
-		urb = usb_alloc_urb(0, GFP_KERNEL);
-		if (!urb) {
-			kfree(unode);
-			break;
-		}
-		unode->urb = urb;
-
-		buf = usb_alloc_coherent(dev->udev, MAX_TRANSFER, GFP_KERNEL,
-					 &urb->transfer_dma);
-		if (!buf) {
-			kfree(unode);
-			usb_free_urb(urb);
-			break;
-		}
-
-		/* urb->transfer_buffer_length set to actual before submit */
-		usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 1),
-			buf, size, dlfb_urb_completion, unode);
-		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
-
-		list_add_tail(&unode->entry, &dev->urbs.list);
-
-		i++;
-	}
-
-	sema_init(&dev->urbs.limit_sem, i);
-	dev->urbs.count = i;
-	dev->urbs.available = i;
-
-	dl_notice("allocated %d %d byte urbs\n", i, (int) size);
-
-	return i;
-}
-
-static struct urb *dlfb_get_urb(struct dlfb_data *dev)
-{
-	int ret = 0;
-	struct list_head *entry;
-	struct urb_node *unode;
-	struct urb *urb = NULL;
-	unsigned long flags;
-
-	/* Wait for an in-flight buffer to complete and get re-queued */
-	ret = down_timeout(&dev->urbs.limit_sem, GET_URB_TIMEOUT);
-	if (ret) {
-		atomic_set(&dev->lost_pixels, 1);
-		dl_warn("wait for urb interrupted: %x available: %d\n",
-		       ret, dev->urbs.available);
-		goto error;
-	}
-
-	spin_lock_irqsave(&dev->urbs.lock, flags);
-
-	BUG_ON(list_empty(&dev->urbs.list)); /* reserved one with limit_sem */
-	entry = dev->urbs.list.next;
-	list_del_init(entry);
-	dev->urbs.available--;
-
-	spin_unlock_irqrestore(&dev->urbs.lock, flags);
-
-	unode = list_entry(entry, struct urb_node, entry);
-	urb = unode->urb;
-
-error:
-	return urb;
-}
-
-static int dlfb_submit_urb(struct dlfb_data *dev, struct urb *urb, size_t len)
-{
-	int ret;
-
-	BUG_ON(len > dev->urbs.size);
-
-	urb->transfer_buffer_length = len; /* set to actual payload len */
-	ret = usb_submit_urb(urb, GFP_KERNEL);
-	if (ret) {
-		dlfb_urb_completion(urb); /* because no one else will */
-		atomic_set(&dev->lost_pixels, 1);
-		dl_err("usb_submit_urb error %x\n", ret);
-	}
-	return ret;
-}
-
-module_param(console, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
-MODULE_PARM_DESC(console, "Allow fbcon to consume first framebuffer found");
-
-module_param(fb_defio, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
-MODULE_PARM_DESC(fb_defio, "Enable fb_defio mmap support. *Experimental*");
-
-MODULE_AUTHOR("Roberto De Ioris <roberto@unbit.it>, "
-	      "Jaya Kumar <jayakumar.lkml@gmail.com>, "
-	      "Bernie Thompson <bernie@plugable.com>");
-MODULE_DESCRIPTION("DisplayLink kernel framebuffer driver");
-MODULE_LICENSE("GPL");
-
diff --git a/drivers/staging/udlfb/udlfb.h b/drivers/staging/udlfb/udlfb.h
deleted file mode 100644
index 6f9785e9d62e..000000000000
--- a/drivers/staging/udlfb/udlfb.h
+++ /dev/null
@@ -1,117 +0,0 @@
-#ifndef UDLFB_H
-#define UDLFB_H
-
-/*
- * TODO: Propose standard fb.h ioctl for reporting damage,
- * using _IOWR() and one of the existing area structs from fb.h
- * Consider these ioctls deprecated, but they're still used by the
- * DisplayLink X server as yet - need both to be modified in tandem
- * when new ioctl(s) are ready.
- */
-#define DLFB_IOCTL_RETURN_EDID	 0xAD
-#define DLFB_IOCTL_REPORT_DAMAGE 0xAA
-struct dloarea {
-	int x, y;
-	int w, h;
-	int x2, y2;
-};
-
-struct urb_node {
-	struct list_head entry;
-	struct dlfb_data *dev;
-	struct delayed_work release_urb_work;
-	struct urb *urb;
-};
-
-struct urb_list {
-	struct list_head list;
-	spinlock_t lock;
-	struct semaphore limit_sem;
-	int available;
-	int count;
-	size_t size;
-};
-
-struct dlfb_data {
-	struct usb_device *udev;
-	struct device *gdev; /* &udev->dev */
-	struct fb_info *info;
-	struct urb_list urbs;
-	struct kref kref;
-	char *backing_buffer;
-	int fb_count;
-	bool virtualized; /* true when physical usb device not present */
-	struct delayed_work free_framebuffer_work;
-	atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */
-	atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */
-	char *edid; /* null until we read edid from hw or get from sysfs */
-	size_t edid_size;
-	int sku_pixel_limit;
-	int base16;
-	int base8;
-	u32 pseudo_palette[256];
-	/* blit-only rendering path metrics, exposed through sysfs */
-	atomic_t bytes_rendered; /* raw pixel-bytes driver asked to render */
-	atomic_t bytes_identical; /* saved effort with backbuffer comparison */
-	atomic_t bytes_sent; /* to usb, after compression including overhead */
-	atomic_t cpu_kcycles_used; /* transpired during pixel processing */
-};
-
-#define NR_USB_REQUEST_I2C_SUB_IO 0x02
-#define NR_USB_REQUEST_CHANNEL 0x12
-
-/* -BULK_SIZE as per usb-skeleton. Can we get full page and avoid overhead? */
-#define BULK_SIZE 512
-#define MAX_TRANSFER (PAGE_SIZE*16 - BULK_SIZE)
-#define WRITES_IN_FLIGHT (4)
-
-#define MIN_EDID_SIZE 128
-#define MAX_EDID_SIZE 128
-
-#define MAX_VENDOR_DESCRIPTOR_SIZE 256
-
-#define GET_URB_TIMEOUT	HZ
-#define FREE_URB_TIMEOUT (HZ*2)
-
-#define BPP                     2
-#define MAX_CMD_PIXELS		255
-
-#define RLX_HEADER_BYTES	7
-#define MIN_RLX_PIX_BYTES       4
-#define MIN_RLX_CMD_BYTES	(RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
-
-#define RLE_HEADER_BYTES	6
-#define MIN_RLE_PIX_BYTES	3
-#define MIN_RLE_CMD_BYTES	(RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
-
-#define RAW_HEADER_BYTES	6
-#define MIN_RAW_PIX_BYTES	2
-#define MIN_RAW_CMD_BYTES	(RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
-
-#define DL_DEFIO_WRITE_DELAY    5 /* fb_deferred_io.delay in jiffies */
-#define DL_DEFIO_WRITE_DISABLE  (HZ*60) /* "disable" with long delay */
-
-/* remove these once align.h patch is taken into kernel */
-#define DL_ALIGN_UP(x, a) ALIGN(x, a)
-#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
-
-/* remove once this gets added to sysfs.h */
-#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
-
-/*
- * udlfb is both a usb device, and a framebuffer device.
- * They may exist at the same time, but during various stages
- * inactivity, teardown, or "virtual" operation, only one or the
- * other will exist (one will outlive the other).  So we can't
- * call the dev_*() macros, because we don't have a stable dev object.
- */
-#define dl_err(format, arg...) \
-	pr_err("udlfb: " format, ## arg)
-#define dl_warn(format, arg...) \
-	pr_warning("udlfb: " format, ## arg)
-#define dl_notice(format, arg...) \
-	pr_notice("udlfb: " format, ## arg)
-#define dl_info(format, arg...) \
-	pr_info("udlfb: " format, ## arg)
-
-#endif
diff --git a/drivers/staging/udlfb/udlfb.txt b/drivers/staging/udlfb/udlfb.txt
deleted file mode 100644
index 7fdde2a02a27..000000000000
--- a/drivers/staging/udlfb/udlfb.txt
+++ /dev/null
@@ -1,144 +0,0 @@
-
-What is udlfb?
-===============
-
-This is a driver for DisplayLink USB 2.0 era graphics chips.
-
-DisplayLink chips provide simple hline/blit operations with some compression,
-pairing that with a hardware framebuffer (16MB) on the other end of the
-USB wire.  That hardware framebuffer is able to drive the VGA, DVI, or HDMI
-monitor with no CPU involvement until a pixel has to change.
-
-The CPU or other local resource does all the rendering; optinally compares the
-result with a local shadow of the remote hardware framebuffer to identify
-the minimal set of pixels that have changed; and compresses and sends those
-pixels line-by-line via USB bulk transfers.
-
-Because of the efficiency of bulk transfers and a protocol on top that
-does not require any acks - the effect is very low latency that
-can support surprisingly high resolutions with good performance for
-non-gaming and non-video applications.
-
-Mode setting, EDID read, etc are other bulk or control transfers. Mode
-setting is very flexible - able to set nearly arbitrary modes from any timing.
-
-Advantages of USB graphics in general:
-
- * Ability to add a nearly arbitrary number of displays to any USB 2.0
-   capable system. On Linux, number of displays is limited by fbdev interface
-   (FB_MAX is currently 32). Of course, all USB devices on the same
-   host controller share the same 480Mbs USB 2.0 interface.
-
-Advantages of supporting DisplayLink chips with kernel framebuffer interface:
-
- * The actual hardware functionality of DisplayLink chips matches nearly
-   one-to-one with the fbdev interface, making the driver quite small and
-   tight relative to the functionality it provides.
- * X servers and other applications can use the standard fbdev interface
-   from user mode to talk to the device, without needing to know anything
-   about USB or DisplayLink's protocol at all. A "displaylink" X driver
-   and a slightly modified "fbdev" X driver are among those that already do.
-
-Disadvantages:
-
- * Fbdev's mmap interface assumes a real hardware framebuffer is mapped.
-   In the case of USB graphics, it is just an allocated (virtual) buffer.
-   Writes need to be detected and encoded into USB bulk transfers by the CPU.
-   Accurate damage/changed area notifications work around this problem.
-   In the future, hopefully fbdev will be enhanced with an small standard
-   interface to allow mmap clients to report damage, for the benefit
-   of virtual or remote framebuffers.
- * Fbdev does not arbitrate client ownership of the framebuffer well.
- * Fbcon assumes the first framebuffer it finds should be consumed for console.
- * It's not clear what the future of fbdev is, given the rise of KMS/DRM.
-
-How to use it?
-==============
-
-Udlfb, when loaded as a module, will match against all USB 2.0 generation
-DisplayLink chips (Alex and Ollie family). It will then attempt to read the EDID
-of the monitor, and set the best common mode between the DisplayLink device
-and the monitor's capabilities.
-
-If the DisplayLink device is successful, it will paint a "green screen" which
-means that from a hardware and fbdev software perspective, everything is good.
-
-At that point, a /dev/fb? interface will be present for user-mode applications
-to open and begin writing to the framebuffer of the DisplayLink device using
-standard fbdev calls.  Note that if mmap() is used, by default the user mode
-application must send down damage notifcations to trigger repaints of the
-changed regions.  Alternatively, udlfb can be recompiled with experimental
-defio support enabled, to support a page-fault based detection mechanism
-that can work without explicit notifcation.
-
-The most common client of udlfb is xf86-video-displaylink or a modified
-xf86-video-fbdev X server. These servers have no real DisplayLink specific
-code. They write to the standard framebuffer interface and rely on udlfb
-to do its thing.  The one extra feature they have is the ability to report
-rectangles from the X DAMAGE protocol extension down to udlfb via udlfb's
-damage interface (which will hopefully be standardized for all virtual
-framebuffers that need damage info). These damage notifications allow
-udlfb to efficiently process the changed pixels.
-
-Module Options
-==============
-
-Special configuration for udlfb is usually unnecessary. There are a few
-options, however.
-
-From the command line, pass options to modprobe
-modprobe udlfb defio=1 console=1
-
-Or for permanent option, create file like /etc/modprobe.d/options with text
-options udlfb defio=1 console=1
-
-Accepted options:
-
-fb_defio	Make use of the fb_defio (CONFIG_FB_DEFERRED_IO) kernel
-		module to track changed areas of the framebuffer by page faults.
-        	Standard fbdev applications that use mmap but that do not
-		report damage, may be able to work with this enabled.
-		Disabled by default because of overhead and other issues.
-
-console		Allow fbcon to attach to udlfb provided framebuffers. This
-		is disabled by default because fbcon will aggressively consume
-		the first framebuffer it finds, which isn't usually what the
-		user wants in the case of USB displays.
-
-Sysfs Attributes
-================
-
-Udlfb creates several files in /sys/class/graphics/fb?
-Where ? is the sequential framebuffer id of the particular DisplayLink device
-
-edid	       		If a valid EDID blob is written to this file (typically
-			by a udev rule), then udlfb will use this EDID as a
-			backup in case reading the actual EDID of the monitor
-			attached to the DisplayLink device fails. This is
-			especially useful for fixed panels, etc. that cannot
-			communicate their capabilities via EDID. Reading
-			this file returns the current EDID of the attached
-			monitor (or last backup value written). This is
-			useful to get the EDID of the attached monitor,
-			which can be passed to utilities like parse-edid.
-
-metrics_bytes_rendered	32-bit count of pixel bytes rendered
-
-metrics_bytes_identical 32-bit count of how many of those bytes were found to be
-			unchanged, based on a shadow framebuffer check
-
-metrics_bytes_sent	32-bit count of how many bytes were transferred over
-			USB to communicate the resulting changed pixels to the
-			hardware. Includes compression and protocol overhead
-
-metrics_cpu_kcycles_used 32-bit count of CPU cycles used in processing the
-			above pixels (in thousands of cycles).
-
-metrics_reset		Write-only. Any write to this file resets all metrics
-			above to zero.  Note that the 32-bit counters above
-			roll over very quickly. To get reliable results, design
-			performance tests to start and finish in a very short
-			period of time (one minute or less is safe).
-
---
-Bernie Thompson <bernie@plugable.com>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 27c1fb4b1e0d..37771d0916ef 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -2034,6 +2034,20 @@ config FB_SM501
 
 	  If unsure, say N.
 
+config FB_UDL
+	tristate "Displaylink USB Framebuffer support"
+	depends on FB && USB
+	select FB_MODE_HELPERS
+	select FB_SYS_FILLRECT
+	select FB_SYS_COPYAREA
+	select FB_SYS_IMAGEBLIT
+	select FB_SYS_FOPS
+	select FB_DEFERRED_IO
+	---help---
+	  This is a kernel framebuffer driver for DisplayLink USB devices.
+	  Supports fbdev clients like xf86-video-fbdev, kdrive, fbi, and
+	  mplayer -vo fbdev. Supports all USB 2.0 era DisplayLink devices.
+	  To compile as a module, choose M here: the module name is udlfb.
 
 config FB_PNX4008_DUM
 	tristate "Display Update Module support on Philips PNX4008 board"
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 485e8ed1318c..03678e3021ab 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -122,6 +122,7 @@ obj-$(CONFIG_FB_PNX4008_DUM_RGB)  += pnx4008/
 obj-$(CONFIG_FB_IBM_GXT4500)	  += gxt4500.o
 obj-$(CONFIG_FB_PS3)		  += ps3fb.o
 obj-$(CONFIG_FB_SM501)            += sm501fb.o
+obj-$(CONFIG_FB_UDL)		  += udlfb.o
 obj-$(CONFIG_FB_XILINX)           += xilinxfb.o
 obj-$(CONFIG_SH_MIPI_DSI)	  += sh_mipi_dsi.o
 obj-$(CONFIG_FB_SH_MOBILE_HDMI)	  += sh_mobile_hdmi.o
diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
new file mode 100644
index 000000000000..0cca4873d490
--- /dev/null
+++ b/drivers/video/udlfb.c
@@ -0,0 +1,1915 @@
+/*
+ * udlfb.c -- Framebuffer driver for DisplayLink USB controller
+ *
+ * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
+ * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
+ * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License v2. See the file COPYING in the main directory of this archive for
+ * more details.
+ *
+ * Layout is based on skeletonfb by James Simmons and Geert Uytterhoeven,
+ * usb-skeleton by GregKH.
+ *
+ * Device-specific portions based on information from Displaylink, with work
+ * from Florian Echtler, Henrik Bjerregaard Pedersen, and others.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/usb.h>
+#include <linux/uaccess.h>
+#include <linux/mm.h>
+#include <linux/fb.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <video/udlfb.h>
+
+static struct fb_fix_screeninfo dlfb_fix = {
+	.id =           "udlfb",
+	.type =         FB_TYPE_PACKED_PIXELS,
+	.visual =       FB_VISUAL_TRUECOLOR,
+	.xpanstep =     0,
+	.ypanstep =     0,
+	.ywrapstep =    0,
+	.accel =        FB_ACCEL_NONE,
+};
+
+static const u32 udlfb_info_flags = FBINFO_DEFAULT | FBINFO_READS_FAST |
+#ifdef FBINFO_VIRTFB
+		FBINFO_VIRTFB |
+#endif
+		FBINFO_HWACCEL_IMAGEBLIT | FBINFO_HWACCEL_FILLRECT |
+		FBINFO_HWACCEL_COPYAREA | FBINFO_MISC_ALWAYS_SETPAR;
+
+/*
+ * There are many DisplayLink-based products, all with unique PIDs. We are able
+ * to support all volume ones (circa 2009) with a single driver, so we match
+ * globally on VID. TODO: Probe() needs to detect when we might be running
+ * "future" chips, and bail on those, so a compatible driver can match.
+ */
+static struct usb_device_id id_table[] = {
+	{.idVendor = 0x17e9, .match_flags = USB_DEVICE_ID_MATCH_VENDOR,},
+	{},
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+/* module options */
+static int console;   /* Optionally allow fbcon to consume first framebuffer */
+static int fb_defio;  /* Optionally enable experimental fb_defio mmap support */
+
+/* dlfb keeps a list of urbs for efficient bulk transfers */
+static void dlfb_urb_completion(struct urb *urb);
+static struct urb *dlfb_get_urb(struct dlfb_data *dev);
+static int dlfb_submit_urb(struct dlfb_data *dev, struct urb * urb, size_t len);
+static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size);
+static void dlfb_free_urb_list(struct dlfb_data *dev);
+
+/*
+ * All DisplayLink bulk operations start with 0xAF, followed by specific code
+ * All operations are written to buffers which then later get sent to device
+ */
+static char *dlfb_set_register(char *buf, u8 reg, u8 val)
+{
+	*buf++ = 0xAF;
+	*buf++ = 0x20;
+	*buf++ = reg;
+	*buf++ = val;
+	return buf;
+}
+
+static char *dlfb_vidreg_lock(char *buf)
+{
+	return dlfb_set_register(buf, 0xFF, 0x00);
+}
+
+static char *dlfb_vidreg_unlock(char *buf)
+{
+	return dlfb_set_register(buf, 0xFF, 0xFF);
+}
+
+/*
+ * On/Off for driving the DisplayLink framebuffer to the display
+ *  0x00 H and V sync on
+ *  0x01 H and V sync off (screen blank but powered)
+ *  0x07 DPMS powerdown (requires modeset to come back)
+ */
+static char *dlfb_enable_hvsync(char *buf, bool enable)
+{
+	if (enable)
+		return dlfb_set_register(buf, 0x1F, 0x00);
+	else
+		return dlfb_set_register(buf, 0x1F, 0x07);
+}
+
+static char *dlfb_set_color_depth(char *buf, u8 selection)
+{
+	return dlfb_set_register(buf, 0x00, selection);
+}
+
+static char *dlfb_set_base16bpp(char *wrptr, u32 base)
+{
+	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
+	wrptr = dlfb_set_register(wrptr, 0x20, base >> 16);
+	wrptr = dlfb_set_register(wrptr, 0x21, base >> 8);
+	return dlfb_set_register(wrptr, 0x22, base);
+}
+
+/*
+ * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
+ * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
+ */
+static char *dlfb_set_base8bpp(char *wrptr, u32 base)
+{
+	wrptr = dlfb_set_register(wrptr, 0x26, base >> 16);
+	wrptr = dlfb_set_register(wrptr, 0x27, base >> 8);
+	return dlfb_set_register(wrptr, 0x28, base);
+}
+
+static char *dlfb_set_register_16(char *wrptr, u8 reg, u16 value)
+{
+	wrptr = dlfb_set_register(wrptr, reg, value >> 8);
+	return dlfb_set_register(wrptr, reg+1, value);
+}
+
+/*
+ * This is kind of weird because the controller takes some
+ * register values in a different byte order than other registers.
+ */
+static char *dlfb_set_register_16be(char *wrptr, u8 reg, u16 value)
+{
+	wrptr = dlfb_set_register(wrptr, reg, value);
+	return dlfb_set_register(wrptr, reg+1, value >> 8);
+}
+
+/*
+ * LFSR is linear feedback shift register. The reason we have this is
+ * because the display controller needs to minimize the clock depth of
+ * various counters used in the display path. So this code reverses the
+ * provided value into the lfsr16 value by counting backwards to get
+ * the value that needs to be set in the hardware comparator to get the
+ * same actual count. This makes sense once you read above a couple of
+ * times and think about it from a hardware perspective.
+ */
+static u16 dlfb_lfsr16(u16 actual_count)
+{
+	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */
+
+	while (actual_count--) {
+		lv =	 ((lv << 1) |
+			(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
+			& 0xFFFF;
+	}
+
+	return (u16) lv;
+}
+
+/*
+ * This does LFSR conversion on the value that is to be written.
+ * See LFSR explanation above for more detail.
+ */
+static char *dlfb_set_register_lfsr16(char *wrptr, u8 reg, u16 value)
+{
+	return dlfb_set_register_16(wrptr, reg, dlfb_lfsr16(value));
+}
+
+/*
+ * This takes a standard fbdev screeninfo struct and all of its monitor mode
+ * details and converts them into the DisplayLink equivalent register commands.
+ */
+static char *dlfb_set_vid_cmds(char *wrptr, struct fb_var_screeninfo *var)
+{
+	u16 xds, yds;
+	u16 xde, yde;
+	u16 yec;
+
+	/* x display start */
+	xds = var->left_margin + var->hsync_len;
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x01, xds);
+	/* x display end */
+	xde = xds + var->xres;
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x03, xde);
+
+	/* y display start */
+	yds = var->upper_margin + var->vsync_len;
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x05, yds);
+	/* y display end */
+	yde = yds + var->yres;
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x07, yde);
+
+	/* x end count is active + blanking - 1 */
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x09,
+			xde + var->right_margin - 1);
+
+	/* libdlo hardcodes hsync start to 1 */
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0B, 1);
+
+	/* hsync end is width of sync pulse + 1 */
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0D, var->hsync_len + 1);
+
+	/* hpixels is active pixels */
+	wrptr = dlfb_set_register_16(wrptr, 0x0F, var->xres);
+
+	/* yendcount is vertical active + vertical blanking */
+	yec = var->yres + var->upper_margin + var->lower_margin +
+			var->vsync_len;
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x11, yec);
+
+	/* libdlo hardcodes vsync start to 0 */
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x13, 0);
+
+	/* vsync end is width of vsync pulse */
+	wrptr = dlfb_set_register_lfsr16(wrptr, 0x15, var->vsync_len);
+
+	/* vpixels is active pixels */
+	wrptr = dlfb_set_register_16(wrptr, 0x17, var->yres);
+
+	/* convert picoseconds to 5kHz multiple for pclk5k = x * 1E12/5k */
+	wrptr = dlfb_set_register_16be(wrptr, 0x1B,
+			200*1000*1000/var->pixclock);
+
+	return wrptr;
+}
+
+/*
+ * This takes a standard fbdev screeninfo struct that was fetched or prepared
+ * and then generates the appropriate command sequence that then drives the
+ * display controller.
+ */
+static int dlfb_set_video_mode(struct dlfb_data *dev,
+				struct fb_var_screeninfo *var)
+{
+	char *buf;
+	char *wrptr;
+	int retval = 0;
+	int writesize;
+	struct urb *urb;
+
+	if (!atomic_read(&dev->usb_active))
+		return -EPERM;
+
+	urb = dlfb_get_urb(dev);
+	if (!urb)
+		return -ENOMEM;
+
+	buf = (char *) urb->transfer_buffer;
+
+	/*
+	* This first section has to do with setting the base address on the
+	* controller * associated with the display. There are 2 base
+	* pointers, currently, we only * use the 16 bpp segment.
+	*/
+	wrptr = dlfb_vidreg_lock(buf);
+	wrptr = dlfb_set_color_depth(wrptr, 0x00);
+	/* set base for 16bpp segment to 0 */
+	wrptr = dlfb_set_base16bpp(wrptr, 0);
+	/* set base for 8bpp segment to end of fb */
+	wrptr = dlfb_set_base8bpp(wrptr, dev->info->fix.smem_len);
+
+	wrptr = dlfb_set_vid_cmds(wrptr, var);
+	wrptr = dlfb_enable_hvsync(wrptr, true);
+	wrptr = dlfb_vidreg_unlock(wrptr);
+
+	writesize = wrptr - buf;
+
+	retval = dlfb_submit_urb(dev, urb, writesize);
+
+	return retval;
+}
+
+static int dlfb_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	unsigned long start = vma->vm_start;
+	unsigned long size = vma->vm_end - vma->vm_start;
+	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+	unsigned long page, pos;
+
+	if (offset + size > info->fix.smem_len)
+		return -EINVAL;
+
+	pos = (unsigned long)info->fix.smem_start + offset;
+
+	dl_notice("mmap() framebuffer addr:%lu size:%lu\n",
+		  pos, size);
+
+	while (size > 0) {
+		page = vmalloc_to_pfn((void *)pos);
+		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
+			return -EAGAIN;
+
+		start += PAGE_SIZE;
+		pos += PAGE_SIZE;
+		if (size > PAGE_SIZE)
+			size -= PAGE_SIZE;
+		else
+			size = 0;
+	}
+
+	vma->vm_flags |= VM_RESERVED;	/* avoid to swap out this VMA */
+	return 0;
+}
+
+/*
+ * Trims identical data from front and back of line
+ * Sets new front buffer address and width
+ * And returns byte count of identical pixels
+ * Assumes CPU natural alignment (unsigned long)
+ * for back and front buffer ptrs and width
+ */
+static int dlfb_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
+{
+	int j, k;
+	const unsigned long *back = (const unsigned long *) bback;
+	const unsigned long *front = (const unsigned long *) *bfront;
+	const int width = *width_bytes / sizeof(unsigned long);
+	int identical = width;
+	int start = width;
+	int end = width;
+
+	prefetch((void *) front);
+	prefetch((void *) back);
+
+	for (j = 0; j < width; j++) {
+		if (back[j] != front[j]) {
+			start = j;
+			break;
+		}
+	}
+
+	for (k = width - 1; k > j; k--) {
+		if (back[k] != front[k]) {
+			end = k+1;
+			break;
+		}
+	}
+
+	identical = start + (width - end);
+	*bfront = (u8 *) &front[start];
+	*width_bytes = (end - start) * sizeof(unsigned long);
+
+	return identical * sizeof(unsigned long);
+}
+
+/*
+ * Render a command stream for an encoded horizontal line segment of pixels.
+ *
+ * A command buffer holds several commands.
+ * It always begins with a fresh command header
+ * (the protocol doesn't require this, but we enforce it to allow
+ * multiple buffers to be potentially encoded and sent in parallel).
+ * A single command encodes one contiguous horizontal line of pixels
+ *
+ * The function relies on the client to do all allocation, so that
+ * rendering can be done directly to output buffers (e.g. USB URBs).
+ * The function fills the supplied command buffer, providing information
+ * on where it left off, so the client may call in again with additional
+ * buffers if the line will take several buffers to complete.
+ *
+ * A single command can transmit a maximum of 256 pixels,
+ * regardless of the compression ratio (protocol design limit).
+ * To the hardware, 0 for a size byte means 256
+ *
+ * Rather than 256 pixel commands which are either rl or raw encoded,
+ * the rlx command simply assumes alternating raw and rl spans within one cmd.
+ * This has a slightly larger header overhead, but produces more even results.
+ * It also processes all data (read and write) in a single pass.
+ * Performance benchmarks of common cases show it having just slightly better
+ * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
+ * But for very rl friendly data, will compress not quite as well.
+ */
+static void dlfb_compress_hline(
+	const uint16_t **pixel_start_ptr,
+	const uint16_t *const pixel_end,
+	uint32_t *device_address_ptr,
+	uint8_t **command_buffer_ptr,
+	const uint8_t *const cmd_buffer_end)
+{
+	const uint16_t *pixel = *pixel_start_ptr;
+	uint32_t dev_addr  = *device_address_ptr;
+	uint8_t *cmd = *command_buffer_ptr;
+	const int bpp = 2;
+
+	while ((pixel_end > pixel) &&
+	       (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
+		uint8_t *raw_pixels_count_byte = 0;
+		uint8_t *cmd_pixels_count_byte = 0;
+		const uint16_t *raw_pixel_start = 0;
+		const uint16_t *cmd_pixel_start, *cmd_pixel_end = 0;
+
+		prefetchw((void *) cmd); /* pull in one cache line at least */
+
+		*cmd++ = 0xAF;
+		*cmd++ = 0x6B;
+		*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
+		*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
+		*cmd++ = (uint8_t) ((dev_addr) & 0xFF);
+
+		cmd_pixels_count_byte = cmd++; /*  we'll know this later */
+		cmd_pixel_start = pixel;
+
+		raw_pixels_count_byte = cmd++; /*  we'll know this later */
+		raw_pixel_start = pixel;
+
+		cmd_pixel_end = pixel + min(MAX_CMD_PIXELS + 1,
+			min((int)(pixel_end - pixel),
+			    (int)(cmd_buffer_end - cmd) / bpp));
+
+		prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
+
+		while (pixel < cmd_pixel_end) {
+			const uint16_t * const repeating_pixel = pixel;
+
+			*(uint16_t *)cmd = cpu_to_be16p(pixel);
+			cmd += 2;
+			pixel++;
+
+			if (unlikely((pixel < cmd_pixel_end) &&
+				     (*pixel == *repeating_pixel))) {
+				/* go back and fill in raw pixel count */
+				*raw_pixels_count_byte = ((repeating_pixel -
+						raw_pixel_start) + 1) & 0xFF;
+
+				while ((pixel < cmd_pixel_end)
+				       && (*pixel == *repeating_pixel)) {
+					pixel++;
+				}
+
+				/* immediately after raw data is repeat byte */
+				*cmd++ = ((pixel - repeating_pixel) - 1) & 0xFF;
+
+				/* Then start another raw pixel span */
+				raw_pixel_start = pixel;
+				raw_pixels_count_byte = cmd++;
+			}
+		}
+
+		if (pixel > raw_pixel_start) {
+			/* finalize last RAW span */
+			*raw_pixels_count_byte = (pixel-raw_pixel_start) & 0xFF;
+		}
+
+		*cmd_pixels_count_byte = (pixel - cmd_pixel_start) & 0xFF;
+		dev_addr += (pixel - cmd_pixel_start) * bpp;
+	}
+
+	if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
+		/* Fill leftover bytes with no-ops */
+		if (cmd_buffer_end > cmd)
+			memset(cmd, 0xAF, cmd_buffer_end - cmd);
+		cmd = (uint8_t *) cmd_buffer_end;
+	}
+
+	*command_buffer_ptr = cmd;
+	*pixel_start_ptr = pixel;
+	*device_address_ptr = dev_addr;
+
+	return;
+}
+
+/*
+ * There are 3 copies of every pixel: The front buffer that the fbdev
+ * client renders to, the actual framebuffer across the USB bus in hardware
+ * (that we can only write to, slowly, and can never read), and (optionally)
+ * our shadow copy that tracks what's been sent to that hardware buffer.
+ */
+static int dlfb_render_hline(struct dlfb_data *dev, struct urb **urb_ptr,
+			      const char *front, char **urb_buf_ptr,
+			      u32 byte_offset, u32 byte_width,
+			      int *ident_ptr, int *sent_ptr)
+{
+	const u8 *line_start, *line_end, *next_pixel;
+	u32 dev_addr = dev->base16 + byte_offset;
+	struct urb *urb = *urb_ptr;
+	u8 *cmd = *urb_buf_ptr;
+	u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
+
+	line_start = (u8 *) (front + byte_offset);
+	next_pixel = line_start;
+	line_end = next_pixel + byte_width;
+
+	if (dev->backing_buffer) {
+		int offset;
+		const u8 *back_start = (u8 *) (dev->backing_buffer
+						+ byte_offset);
+
+		*ident_ptr += dlfb_trim_hline(back_start, &next_pixel,
+			&byte_width);
+
+		offset = next_pixel - line_start;
+		line_end = next_pixel + byte_width;
+		dev_addr += offset;
+		back_start += offset;
+		line_start += offset;
+
+		memcpy((char *)back_start, (char *) line_start,
+		       byte_width);
+	}
+
+	while (next_pixel < line_end) {
+
+		dlfb_compress_hline((const uint16_t **) &next_pixel,
+			     (const uint16_t *) line_end, &dev_addr,
+			(u8 **) &cmd, (u8 *) cmd_end);
+
+		if (cmd >= cmd_end) {
+			int len = cmd - (u8 *) urb->transfer_buffer;
+			if (dlfb_submit_urb(dev, urb, len))
+				return 1; /* lost pixels is set */
+			*sent_ptr += len;
+			urb = dlfb_get_urb(dev);
+			if (!urb)
+				return 1; /* lost_pixels is set */
+			*urb_ptr = urb;
+			cmd = urb->transfer_buffer;
+			cmd_end = &cmd[urb->transfer_buffer_length];
+		}
+	}
+
+	*urb_buf_ptr = cmd;
+
+	return 0;
+}
+
+int dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
+	       int width, int height, char *data)
+{
+	int i, ret;
+	char *cmd;
+	cycles_t start_cycles, end_cycles;
+	int bytes_sent = 0;
+	int bytes_identical = 0;
+	struct urb *urb;
+	int aligned_x;
+
+	start_cycles = get_cycles();
+
+	aligned_x = DL_ALIGN_DOWN(x, sizeof(unsigned long));
+	width = DL_ALIGN_UP(width + (x-aligned_x), sizeof(unsigned long));
+	x = aligned_x;
+
+	if ((width <= 0) ||
+	    (x + width > dev->info->var.xres) ||
+	    (y + height > dev->info->var.yres))
+		return -EINVAL;
+
+	if (!atomic_read(&dev->usb_active))
+		return 0;
+
+	urb = dlfb_get_urb(dev);
+	if (!urb)
+		return 0;
+	cmd = urb->transfer_buffer;
+
+	for (i = y; i < y + height ; i++) {
+		const int line_offset = dev->info->fix.line_length * i;
+		const int byte_offset = line_offset + (x * BPP);
+
+		if (dlfb_render_hline(dev, &urb,
+				      (char *) dev->info->fix.smem_start,
+				      &cmd, byte_offset, width * BPP,
+				      &bytes_identical, &bytes_sent))
+			goto error;
+	}
+
+	if (cmd > (char *) urb->transfer_buffer) {
+		/* Send partial buffer remaining before exiting */
+		int len = cmd - (char *) urb->transfer_buffer;
+		ret = dlfb_submit_urb(dev, urb, len);
+		bytes_sent += len;
+	} else
+		dlfb_urb_completion(urb);
+
+error:
+	atomic_add(bytes_sent, &dev->bytes_sent);
+	atomic_add(bytes_identical, &dev->bytes_identical);
+	atomic_add(width*height*2, &dev->bytes_rendered);
+	end_cycles = get_cycles();
+	atomic_add(((unsigned int) ((end_cycles - start_cycles)
+		    >> 10)), /* Kcycles */
+		   &dev->cpu_kcycles_used);
+
+	return 0;
+}
+
+static ssize_t dlfb_ops_read(struct fb_info *info, char __user *buf,
+			 size_t count, loff_t *ppos)
+{
+	ssize_t result = -ENOSYS;
+
+#if defined CONFIG_FB_SYS_FOPS || defined CONFIG_FB_SYS_FOPS_MODULE
+	result = fb_sys_read(info, buf, count, ppos);
+#endif
+
+	return result;
+}
+
+/*
+ * Path triggered by usermode clients who write to filesystem
+ * e.g. cat filename > /dev/fb1
+ * Not used by X Windows or text-mode console. But useful for testing.
+ * Slow because of extra copy and we must assume all pixels dirty.
+ */
+static ssize_t dlfb_ops_write(struct fb_info *info, const char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	ssize_t result = -ENOSYS;
+	struct dlfb_data *dev = info->par;
+	u32 offset = (u32) *ppos;
+
+#if defined CONFIG_FB_SYS_FOPS || defined CONFIG_FB_SYS_FOPS_MODULE
+
+	result = fb_sys_write(info, buf, count, ppos);
+
+	if (result > 0) {
+		int start = max((int)(offset / info->fix.line_length) - 1, 0);
+		int lines = min((u32)((result / info->fix.line_length) + 1),
+				(u32)info->var.yres);
+
+		dlfb_handle_damage(dev, 0, start, info->var.xres,
+			lines, info->screen_base);
+	}
+#endif
+
+	return result;
+}
+
+/* hardware has native COPY command (see libdlo), but not worth it for fbcon */
+static void dlfb_ops_copyarea(struct fb_info *info,
+				const struct fb_copyarea *area)
+{
+
+	struct dlfb_data *dev = info->par;
+
+#if defined CONFIG_FB_SYS_COPYAREA || defined CONFIG_FB_SYS_COPYAREA_MODULE
+
+	sys_copyarea(info, area);
+
+	dlfb_handle_damage(dev, area->dx, area->dy,
+			area->width, area->height, info->screen_base);
+#endif
+
+}
+
+static void dlfb_ops_imageblit(struct fb_info *info,
+				const struct fb_image *image)
+{
+	struct dlfb_data *dev = info->par;
+
+#if defined CONFIG_FB_SYS_IMAGEBLIT || defined CONFIG_FB_SYS_IMAGEBLIT_MODULE
+
+	sys_imageblit(info, image);
+
+	dlfb_handle_damage(dev, image->dx, image->dy,
+			image->width, image->height, info->screen_base);
+
+#endif
+
+}
+
+static void dlfb_ops_fillrect(struct fb_info *info,
+			  const struct fb_fillrect *rect)
+{
+	struct dlfb_data *dev = info->par;
+
+#if defined CONFIG_FB_SYS_FILLRECT || defined CONFIG_FB_SYS_FILLRECT_MODULE
+
+	sys_fillrect(info, rect);
+
+	dlfb_handle_damage(dev, rect->dx, rect->dy, rect->width,
+			      rect->height, info->screen_base);
+#endif
+
+}
+
+#ifdef CONFIG_FB_DEFERRED_IO
+/*
+ * NOTE: fb_defio.c is holding info->fbdefio.mutex
+ *   Touching ANY framebuffer memory that triggers a page fault
+ *   in fb_defio will cause a deadlock, when it also tries to
+ *   grab the same mutex.
+ */
+static void dlfb_dpy_deferred_io(struct fb_info *info,
+				struct list_head *pagelist)
+{
+	struct page *cur;
+	struct fb_deferred_io *fbdefio = info->fbdefio;
+	struct dlfb_data *dev = info->par;
+	struct urb *urb;
+	char *cmd;
+	cycles_t start_cycles, end_cycles;
+	int bytes_sent = 0;
+	int bytes_identical = 0;
+	int bytes_rendered = 0;
+
+	if (!fb_defio)
+		return;
+
+	if (!atomic_read(&dev->usb_active))
+		return;
+
+	start_cycles = get_cycles();
+
+	urb = dlfb_get_urb(dev);
+	if (!urb)
+		return;
+
+	cmd = urb->transfer_buffer;
+
+	/* walk the written page list and render each to device */
+	list_for_each_entry(cur, &fbdefio->pagelist, lru) {
+
+		if (dlfb_render_hline(dev, &urb, (char *) info->fix.smem_start,
+				  &cmd, cur->index << PAGE_SHIFT,
+				  PAGE_SIZE, &bytes_identical, &bytes_sent))
+			goto error;
+		bytes_rendered += PAGE_SIZE;
+	}
+
+	if (cmd > (char *) urb->transfer_buffer) {
+		/* Send partial buffer remaining before exiting */
+		int len = cmd - (char *) urb->transfer_buffer;
+		dlfb_submit_urb(dev, urb, len);
+		bytes_sent += len;
+	} else
+		dlfb_urb_completion(urb);
+
+error:
+	atomic_add(bytes_sent, &dev->bytes_sent);
+	atomic_add(bytes_identical, &dev->bytes_identical);
+	atomic_add(bytes_rendered, &dev->bytes_rendered);
+	end_cycles = get_cycles();
+	atomic_add(((unsigned int) ((end_cycles - start_cycles)
+		    >> 10)), /* Kcycles */
+		   &dev->cpu_kcycles_used);
+}
+
+#endif
+
+static int dlfb_get_edid(struct dlfb_data *dev, char *edid, int len)
+{
+	int i;
+	int ret;
+	char *rbuf;
+
+	rbuf = kmalloc(2, GFP_KERNEL);
+	if (!rbuf)
+		return 0;
+
+	for (i = 0; i < len; i++) {
+		ret = usb_control_msg(dev->udev,
+				    usb_rcvctrlpipe(dev->udev, 0), (0x02),
+				    (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
+				    HZ);
+		if (ret < 1) {
+			dl_err("Read EDID byte %d failed err %x\n", i, ret);
+			i--;
+			break;
+		}
+		edid[i] = rbuf[1];
+	}
+
+	kfree(rbuf);
+
+	return i;
+}
+
+static int dlfb_ops_ioctl(struct fb_info *info, unsigned int cmd,
+				unsigned long arg)
+{
+
+	struct dlfb_data *dev = info->par;
+	struct dloarea *area = NULL;
+
+	if (!atomic_read(&dev->usb_active))
+		return 0;
+
+	/* TODO: Update X server to get this from sysfs instead */
+	if (cmd == DLFB_IOCTL_RETURN_EDID) {
+		char *edid = (char *)arg;
+		if (copy_to_user(edid, dev->edid, dev->edid_size))
+			return -EFAULT;
+		return 0;
+	}
+
+	/* TODO: Help propose a standard fb.h ioctl to report mmap damage */
+	if (cmd == DLFB_IOCTL_REPORT_DAMAGE) {
+
+		/*
+		 * If we have a damage-aware client, turn fb_defio "off"
+		 * To avoid perf imact of unecessary page fault handling.
+		 * Done by resetting the delay for this fb_info to a very
+		 * long period. Pages will become writable and stay that way.
+		 * Reset to normal value when all clients have closed this fb.
+		 */
+		if (info->fbdefio)
+			info->fbdefio->delay = DL_DEFIO_WRITE_DISABLE;
+
+		area = (struct dloarea *)arg;
+
+		if (area->x < 0)
+			area->x = 0;
+
+		if (area->x > info->var.xres)
+			area->x = info->var.xres;
+
+		if (area->y < 0)
+			area->y = 0;
+
+		if (area->y > info->var.yres)
+			area->y = info->var.yres;
+
+		dlfb_handle_damage(dev, area->x, area->y, area->w, area->h,
+			   info->screen_base);
+	}
+
+	return 0;
+}
+
+/* taken from vesafb */
+static int
+dlfb_ops_setcolreg(unsigned regno, unsigned red, unsigned green,
+	       unsigned blue, unsigned transp, struct fb_info *info)
+{
+	int err = 0;
+
+	if (regno >= info->cmap.len)
+		return 1;
+
+	if (regno < 16) {
+		if (info->var.red.offset == 10) {
+			/* 1:5:5:5 */
+			((u32 *) (info->pseudo_palette))[regno] =
+			    ((red & 0xf800) >> 1) |
+			    ((green & 0xf800) >> 6) | ((blue & 0xf800) >> 11);
+		} else {
+			/* 0:5:6:5 */
+			((u32 *) (info->pseudo_palette))[regno] =
+			    ((red & 0xf800)) |
+			    ((green & 0xfc00) >> 5) | ((blue & 0xf800) >> 11);
+		}
+	}
+
+	return err;
+}
+
+/*
+ * It's common for several clients to have framebuffer open simultaneously.
+ * e.g. both fbcon and X. Makes things interesting.
+ * Assumes caller is holding info->lock (for open and release at least)
+ */
+static int dlfb_ops_open(struct fb_info *info, int user)
+{
+	struct dlfb_data *dev = info->par;
+
+	/*
+	 * fbcon aggressively connects to first framebuffer it finds,
+	 * preventing other clients (X) from working properly. Usually
+	 * not what the user wants. Fail by default with option to enable.
+	 */
+	if ((user == 0) & (!console))
+		return -EBUSY;
+
+	/* If the USB device is gone, we don't accept new opens */
+	if (dev->virtualized)
+		return -ENODEV;
+
+	dev->fb_count++;
+
+	kref_get(&dev->kref);
+
+#ifdef CONFIG_FB_DEFERRED_IO
+	if (fb_defio && (info->fbdefio == NULL)) {
+		/* enable defio at last moment if not disabled by client */
+
+		struct fb_deferred_io *fbdefio;
+
+		fbdefio = kmalloc(sizeof(struct fb_deferred_io), GFP_KERNEL);
+
+		if (fbdefio) {
+			fbdefio->delay = DL_DEFIO_WRITE_DELAY;
+			fbdefio->deferred_io = dlfb_dpy_deferred_io;
+		}
+
+		info->fbdefio = fbdefio;
+		fb_deferred_io_init(info);
+	}
+#endif
+
+	dl_notice("open /dev/fb%d user=%d fb_info=%p count=%d\n",
+	    info->node, user, info, dev->fb_count);
+
+	return 0;
+}
+
+/*
+ * Called when all client interfaces to start transactions have been disabled,
+ * and all references to our device instance (dlfb_data) are released.
+ * Every transaction must have a reference, so we know are fully spun down
+ */
+static void dlfb_free(struct kref *kref)
+{
+	struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);
+
+	/* this function will wait for all in-flight urbs to complete */
+	if (dev->urbs.count > 0)
+		dlfb_free_urb_list(dev);
+
+	if (dev->backing_buffer)
+		vfree(dev->backing_buffer);
+
+	kfree(dev->edid);
+
+	dl_warn("freeing dlfb_data %p\n", dev);
+
+	kfree(dev);
+}
+
+static void dlfb_release_urb_work(struct work_struct *work)
+{
+	struct urb_node *unode = container_of(work, struct urb_node,
+					      release_urb_work.work);
+
+	up(&unode->dev->urbs.limit_sem);
+}
+
+static void dlfb_free_framebuffer_work(struct work_struct *work)
+{
+	struct dlfb_data *dev = container_of(work, struct dlfb_data,
+					     free_framebuffer_work.work);
+	struct fb_info *info = dev->info;
+	int node = info->node;
+
+	unregister_framebuffer(info);
+
+	if (info->cmap.len != 0)
+		fb_dealloc_cmap(&info->cmap);
+	if (info->monspecs.modedb)
+		fb_destroy_modedb(info->monspecs.modedb);
+	if (info->screen_base)
+		vfree(info->screen_base);
+
+	fb_destroy_modelist(&info->modelist);
+
+	dev->info = 0;
+
+	/* Assume info structure is freed after this point */
+	framebuffer_release(info);
+
+	dl_warn("fb_info for /dev/fb%d has been freed\n", node);
+
+	/* ref taken in probe() as part of registering framebfufer */
+	kref_put(&dev->kref, dlfb_free);
+}
+
+/*
+ * Assumes caller is holding info->lock mutex (for open and release at least)
+ */
+static int dlfb_ops_release(struct fb_info *info, int user)
+{
+	struct dlfb_data *dev = info->par;
+
+	dev->fb_count--;
+
+	/* We can't free fb_info here - fbmem will touch it when we return */
+	if (dev->virtualized && (dev->fb_count == 0))
+		schedule_delayed_work(&dev->free_framebuffer_work, HZ);
+
+#ifdef CONFIG_FB_DEFERRED_IO
+	if ((dev->fb_count == 0) && (info->fbdefio)) {
+		fb_deferred_io_cleanup(info);
+		kfree(info->fbdefio);
+		info->fbdefio = NULL;
+		info->fbops->fb_mmap = dlfb_ops_mmap;
+	}
+#endif
+
+	dl_warn("released /dev/fb%d user=%d count=%d\n",
+		  info->node, user, dev->fb_count);
+
+	kref_put(&dev->kref, dlfb_free);
+
+	return 0;
+}
+
+/*
+ * Check whether a video mode is supported by the DisplayLink chip
+ * We start from monitor's modes, so don't need to filter that here
+ */
+static int dlfb_is_valid_mode(struct fb_videomode *mode,
+		struct fb_info *info)
+{
+	struct dlfb_data *dev = info->par;
+
+	if (mode->xres * mode->yres > dev->sku_pixel_limit) {
+		dl_warn("%dx%d beyond chip capabilities\n",
+		       mode->xres, mode->yres);
+		return 0;
+	}
+
+	dl_info("%dx%d valid mode\n", mode->xres, mode->yres);
+
+	return 1;
+}
+
+static void dlfb_var_color_format(struct fb_var_screeninfo *var)
+{
+	const struct fb_bitfield red = { 11, 5, 0 };
+	const struct fb_bitfield green = { 5, 6, 0 };
+	const struct fb_bitfield blue = { 0, 5, 0 };
+
+	var->bits_per_pixel = 16;
+	var->red = red;
+	var->green = green;
+	var->blue = blue;
+}
+
+static int dlfb_ops_check_var(struct fb_var_screeninfo *var,
+				struct fb_info *info)
+{
+	struct fb_videomode mode;
+
+	/* TODO: support dynamically changing framebuffer size */
+	if ((var->xres * var->yres * 2) > info->fix.smem_len)
+		return -EINVAL;
+
+	/* set device-specific elements of var unrelated to mode */
+	dlfb_var_color_format(var);
+
+	fb_var_to_videomode(&mode, var);
+
+	if (!dlfb_is_valid_mode(&mode, info))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int dlfb_ops_set_par(struct fb_info *info)
+{
+	struct dlfb_data *dev = info->par;
+	int result;
+	u16 *pix_framebuffer;
+	int i;
+
+	dl_notice("set_par mode %dx%d\n", info->var.xres, info->var.yres);
+
+	result = dlfb_set_video_mode(dev, &info->var);
+
+	if ((result == 0) && (dev->fb_count == 0)) {
+
+		/* paint greenscreen */
+
+		pix_framebuffer = (u16 *) info->screen_base;
+		for (i = 0; i < info->fix.smem_len / 2; i++)
+			pix_framebuffer[i] = 0x37e6;
+
+		dlfb_handle_damage(dev, 0, 0, info->var.xres, info->var.yres,
+				   info->screen_base);
+	}
+
+	return result;
+}
+
+/*
+ * In order to come back from full DPMS off, we need to set the mode again
+ */
+static int dlfb_ops_blank(int blank_mode, struct fb_info *info)
+{
+	struct dlfb_data *dev = info->par;
+
+	if (blank_mode != FB_BLANK_UNBLANK) {
+		char *bufptr;
+		struct urb *urb;
+
+		urb = dlfb_get_urb(dev);
+		if (!urb)
+			return 0;
+
+		bufptr = (char *) urb->transfer_buffer;
+		bufptr = dlfb_vidreg_lock(bufptr);
+		bufptr = dlfb_enable_hvsync(bufptr, false);
+		bufptr = dlfb_vidreg_unlock(bufptr);
+
+		dlfb_submit_urb(dev, urb, bufptr -
+				(char *) urb->transfer_buffer);
+	} else {
+		dlfb_set_video_mode(dev, &info->var);
+	}
+
+	return 0;
+}
+
+static struct fb_ops dlfb_ops = {
+	.owner = THIS_MODULE,
+	.fb_read = dlfb_ops_read,
+	.fb_write = dlfb_ops_write,
+	.fb_setcolreg = dlfb_ops_setcolreg,
+	.fb_fillrect = dlfb_ops_fillrect,
+	.fb_copyarea = dlfb_ops_copyarea,
+	.fb_imageblit = dlfb_ops_imageblit,
+	.fb_mmap = dlfb_ops_mmap,
+	.fb_ioctl = dlfb_ops_ioctl,
+	.fb_open = dlfb_ops_open,
+	.fb_release = dlfb_ops_release,
+	.fb_blank = dlfb_ops_blank,
+	.fb_check_var = dlfb_ops_check_var,
+	.fb_set_par = dlfb_ops_set_par,
+};
+
+
+/*
+ * Assumes &info->lock held by caller
+ * Assumes no active clients have framebuffer open
+ */
+static int dlfb_realloc_framebuffer(struct dlfb_data *dev, struct fb_info *info)
+{
+	int retval = -ENOMEM;
+	int old_len = info->fix.smem_len;
+	int new_len;
+	unsigned char *old_fb = info->screen_base;
+	unsigned char *new_fb;
+	unsigned char *new_back;
+
+	dl_warn("Reallocating framebuffer. Addresses will change!\n");
+
+	new_len = info->fix.line_length * info->var.yres;
+
+	if (PAGE_ALIGN(new_len) > old_len) {
+		/*
+		 * Alloc system memory for virtual framebuffer
+		 */
+		new_fb = vmalloc(new_len);
+		if (!new_fb) {
+			dl_err("Virtual framebuffer alloc failed\n");
+			goto error;
+		}
+
+		if (info->screen_base) {
+			memcpy(new_fb, old_fb, old_len);
+			vfree(info->screen_base);
+		}
+
+		info->screen_base = new_fb;
+		info->fix.smem_len = PAGE_ALIGN(new_len);
+		info->fix.smem_start = (unsigned long) new_fb;
+		info->flags = udlfb_info_flags;
+
+		/*
+		 * Second framebuffer copy to mirror the framebuffer state
+		 * on the physical USB device. We can function without this.
+		 * But with imperfect damage info we may send pixels over USB
+		 * that were, in fact, unchanged - wasting limited USB bandwidth
+		 */
+		new_back = vmalloc(new_len);
+		if (!new_back)
+			dl_info("No shadow/backing buffer allcoated\n");
+		else {
+			if (dev->backing_buffer)
+				vfree(dev->backing_buffer);
+			dev->backing_buffer = new_back;
+			memset(dev->backing_buffer, 0, new_len);
+		}
+	}
+
+	retval = 0;
+
+error:
+	return retval;
+}
+
+/*
+ * 1) Get EDID from hw, or use sw default
+ * 2) Parse into various fb_info structs
+ * 3) Allocate virtual framebuffer memory to back highest res mode
+ *
+ * Parses EDID into three places used by various parts of fbdev:
+ * fb_var_screeninfo contains the timing of the monitor's preferred mode
+ * fb_info.monspecs is full parsed EDID info, including monspecs.modedb
+ * fb_info.modelist is a linked list of all monitor & VESA modes which work
+ *
+ * If EDID is not readable/valid, then modelist is all VESA modes,
+ * monspecs is NULL, and fb_var_screeninfo is set to safe VESA mode
+ * Returns 0 if successful
+ */
+static int dlfb_setup_modes(struct dlfb_data *dev,
+			   struct fb_info *info,
+			   char *default_edid, size_t default_edid_size)
+{
+	int i;
+	const struct fb_videomode *default_vmode = NULL;
+	int result = 0;
+	char *edid;
+	int tries = 3;
+
+	if (info->dev) /* only use mutex if info has been registered */
+		mutex_lock(&info->lock);
+
+	edid = kmalloc(MAX_EDID_SIZE, GFP_KERNEL);
+	if (!edid) {
+		result = -ENOMEM;
+		goto error;
+	}
+
+	fb_destroy_modelist(&info->modelist);
+	memset(&info->monspecs, 0, sizeof(info->monspecs));
+
+	/*
+	 * Try to (re)read EDID from hardware first
+	 * EDID data may return, but not parse as valid
+	 * Try again a few times, in case of e.g. analog cable noise
+	 */
+	while (tries--) {
+
+		i = dlfb_get_edid(dev, edid, MAX_EDID_SIZE);
+
+		if (i >= MIN_EDID_SIZE)
+			fb_edid_to_monspecs(edid, &info->monspecs);
+
+		if (info->monspecs.modedb_len > 0) {
+			dev->edid = edid;
+			dev->edid_size = i;
+			break;
+		}
+	}
+
+	/* If that fails, use a previously returned EDID if available */
+	if (info->monspecs.modedb_len == 0) {
+
+		dl_err("Unable to get valid EDID from device/display\n");
+
+		if (dev->edid) {
+			fb_edid_to_monspecs(dev->edid, &info->monspecs);
+			if (info->monspecs.modedb_len > 0)
+				dl_err("Using previously queried EDID\n");
+		}
+	}
+
+	/* If that fails, use the default EDID we were handed */
+	if (info->monspecs.modedb_len == 0) {
+		if (default_edid_size >= MIN_EDID_SIZE) {
+			fb_edid_to_monspecs(default_edid, &info->monspecs);
+			if (info->monspecs.modedb_len > 0) {
+				memcpy(edid, default_edid, default_edid_size);
+				dev->edid = edid;
+				dev->edid_size = default_edid_size;
+				dl_err("Using default/backup EDID\n");
+			}
+		}
+	}
+
+	/* If we've got modes, let's pick a best default mode */
+	if (info->monspecs.modedb_len > 0) {
+
+		for (i = 0; i < info->monspecs.modedb_len; i++) {
+			if (dlfb_is_valid_mode(&info->monspecs.modedb[i], info))
+				fb_add_videomode(&info->monspecs.modedb[i],
+					&info->modelist);
+			else /* if we've removed top/best mode */
+				info->monspecs.misc &= ~FB_MISC_1ST_DETAIL;
+		}
+
+		default_vmode = fb_find_best_display(&info->monspecs,
+						     &info->modelist);
+	}
+
+	/* If everything else has failed, fall back to safe default mode */
+	if (default_vmode == NULL) {
+
+		struct fb_videomode fb_vmode = {0};
+
+		/*
+		 * Add the standard VESA modes to our modelist
+		 * Since we don't have EDID, there may be modes that
+		 * overspec monitor and/or are incorrect aspect ratio, etc.
+		 * But at least the user has a chance to choose
+		 */
+		for (i = 0; i < VESA_MODEDB_SIZE; i++) {
+			if (dlfb_is_valid_mode((struct fb_videomode *)
+						&vesa_modes[i], info))
+				fb_add_videomode(&vesa_modes[i],
+						 &info->modelist);
+		}
+
+		/*
+		 * default to resolution safe for projectors
+		 * (since they are most common case without EDID)
+		 */
+		fb_vmode.xres = 800;
+		fb_vmode.yres = 600;
+		fb_vmode.refresh = 60;
+		default_vmode = fb_find_nearest_mode(&fb_vmode,
+						     &info->modelist);
+	}
+
+	/* If we have good mode and no active clients*/
+	if ((default_vmode != NULL) && (dev->fb_count == 0)) {
+
+		fb_videomode_to_var(&info->var, default_vmode);
+		dlfb_var_color_format(&info->var);
+
+		/*
+		 * with mode size info, we can now alloc our framebuffer.
+		 */
+		memcpy(&info->fix, &dlfb_fix, sizeof(dlfb_fix));
+		info->fix.line_length = info->var.xres *
+			(info->var.bits_per_pixel / 8);
+
+		result = dlfb_realloc_framebuffer(dev, info);
+
+	} else
+		result = -EINVAL;
+
+error:
+	if (edid && (dev->edid != edid))
+		kfree(edid);
+
+	if (info->dev)
+		mutex_unlock(&info->lock);
+
+	return result;
+}
+
+static ssize_t metrics_bytes_rendered_show(struct device *fbdev,
+				   struct device_attribute *a, char *buf) {
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			atomic_read(&dev->bytes_rendered));
+}
+
+static ssize_t metrics_bytes_identical_show(struct device *fbdev,
+				   struct device_attribute *a, char *buf) {
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			atomic_read(&dev->bytes_identical));
+}
+
+static ssize_t metrics_bytes_sent_show(struct device *fbdev,
+				   struct device_attribute *a, char *buf) {
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			atomic_read(&dev->bytes_sent));
+}
+
+static ssize_t metrics_cpu_kcycles_used_show(struct device *fbdev,
+				   struct device_attribute *a, char *buf) {
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			atomic_read(&dev->cpu_kcycles_used));
+}
+
+static ssize_t edid_show(
+			struct file *filp,
+			struct kobject *kobj, struct bin_attribute *a,
+			 char *buf, loff_t off, size_t count) {
+	struct device *fbdev = container_of(kobj, struct device, kobj);
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+
+	if (dev->edid == NULL)
+		return 0;
+
+	if ((off >= dev->edid_size) || (count > dev->edid_size))
+		return 0;
+
+	if (off + count > dev->edid_size)
+		count = dev->edid_size - off;
+
+	dl_info("sysfs edid copy %p to %p, %d bytes\n",
+		dev->edid, buf, (int) count);
+
+	memcpy(buf, dev->edid, count);
+
+	return count;
+}
+
+static ssize_t edid_store(
+			struct file *filp,
+			struct kobject *kobj, struct bin_attribute *a,
+			char *src, loff_t src_off, size_t src_size) {
+	struct device *fbdev = container_of(kobj, struct device, kobj);
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+
+	/* We only support write of entire EDID at once, no offset*/
+	if ((src_size < MIN_EDID_SIZE) ||
+	    (src_size > MAX_EDID_SIZE) ||
+	    (src_off != 0))
+		return 0;
+
+	dlfb_setup_modes(dev, fb_info, src, src_size);
+
+	if (dev->edid && (memcmp(src, dev->edid, src_size) == 0)) {
+		dl_info("sysfs written EDID is new default\n");
+		dlfb_ops_set_par(fb_info);
+		return src_size;
+	} else
+		return 0;
+}
+
+static ssize_t metrics_reset_store(struct device *fbdev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct fb_info *fb_info = dev_get_drvdata(fbdev);
+	struct dlfb_data *dev = fb_info->par;
+
+	atomic_set(&dev->bytes_rendered, 0);
+	atomic_set(&dev->bytes_identical, 0);
+	atomic_set(&dev->bytes_sent, 0);
+	atomic_set(&dev->cpu_kcycles_used, 0);
+
+	return count;
+}
+
+static struct bin_attribute edid_attr = {
+	.attr.name = "edid",
+	.attr.mode = 0666,
+	.size = MAX_EDID_SIZE,
+	.read = edid_show,
+	.write = edid_store
+};
+
+static struct device_attribute fb_device_attrs[] = {
+	__ATTR_RO(metrics_bytes_rendered),
+	__ATTR_RO(metrics_bytes_identical),
+	__ATTR_RO(metrics_bytes_sent),
+	__ATTR_RO(metrics_cpu_kcycles_used),
+	__ATTR(metrics_reset, S_IWUGO, NULL, metrics_reset_store),
+};
+
+/*
+ * This is necessary before we can communicate with the display controller.
+ */
+static int dlfb_select_std_channel(struct dlfb_data *dev)
+{
+	int ret;
+	u8 set_def_chn[] = {	   0x57, 0xCD, 0xDC, 0xA7,
+				0x1C, 0x88, 0x5E, 0x15,
+				0x60, 0xFE, 0xC6, 0x97,
+				0x16, 0x3D, 0x47, 0xF2  };
+
+	ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
+			NR_USB_REQUEST_CHANNEL,
+			(USB_DIR_OUT | USB_TYPE_VENDOR), 0, 0,
+			set_def_chn, sizeof(set_def_chn), USB_CTRL_SET_TIMEOUT);
+	return ret;
+}
+
+static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
+					struct usb_device *usbdev)
+{
+	char *desc;
+	char *buf;
+	char *desc_end;
+
+	u8 total_len = 0;
+
+	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
+	if (!buf)
+		return false;
+	desc = buf;
+
+	total_len = usb_get_descriptor(usbdev, 0x5f, /* vendor specific */
+				    0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
+	if (total_len > 5) {
+		dl_info("vendor descriptor length:%x data:%02x %02x %02x %02x" \
+			"%02x %02x %02x %02x %02x %02x %02x\n",
+			total_len, desc[0],
+			desc[1], desc[2], desc[3], desc[4], desc[5], desc[6],
+			desc[7], desc[8], desc[9], desc[10]);
+
+		if ((desc[0] != total_len) || /* descriptor length */
+		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
+		    (desc[2] != 0x01) ||   /* version (2 bytes) */
+		    (desc[3] != 0x00) ||
+		    (desc[4] != total_len - 2)) /* length after type */
+			goto unrecognized;
+
+		desc_end = desc + total_len;
+		desc += 5; /* the fixed header we've already parsed */
+
+		while (desc < desc_end) {
+			u8 length;
+			u16 key;
+
+			key = *((u16 *) desc);
+			desc += sizeof(u16);
+			length = *desc;
+			desc++;
+
+			switch (key) {
+			case 0x0200: { /* max_area */
+				u32 max_area;
+				max_area = le32_to_cpu(*((u32 *)desc));
+				dl_warn("DL chip limited to %d pixel modes\n",
+					max_area);
+				dev->sku_pixel_limit = max_area;
+				break;
+			}
+			default:
+				break;
+			}
+			desc += length;
+		}
+	}
+
+	goto success;
+
+unrecognized:
+	/* allow udlfb to load for now even if firmware unrecognized */
+	dl_err("Unrecognized vendor firmware descriptor\n");
+
+success:
+	kfree(buf);
+	return true;
+}
+static int dlfb_usb_probe(struct usb_interface *interface,
+			const struct usb_device_id *id)
+{
+	struct usb_device *usbdev;
+	struct dlfb_data *dev = 0;
+	struct fb_info *info = 0;
+	int retval = -ENOMEM;
+	int i;
+
+	/* usb initialization */
+
+	usbdev = interface_to_usbdev(interface);
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (dev == NULL) {
+		err("dlfb_usb_probe: failed alloc of dev struct\n");
+		goto error;
+	}
+
+	/* we need to wait for both usb and fbdev to spin down on disconnect */
+	kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */
+	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */
+
+	dev->udev = usbdev;
+	dev->gdev = &usbdev->dev; /* our generic struct device * */
+	usb_set_intfdata(interface, dev);
+
+	dl_info("%s %s - serial #%s\n",
+		usbdev->manufacturer, usbdev->product, usbdev->serial);
+	dl_info("vid_%04x&pid_%04x&rev_%04x driver's dlfb_data struct at %p\n",
+		usbdev->descriptor.idVendor, usbdev->descriptor.idProduct,
+		usbdev->descriptor.bcdDevice, dev);
+	dl_info("console enable=%d\n", console);
+	dl_info("fb_defio enable=%d\n", fb_defio);
+
+	dev->sku_pixel_limit = 2048 * 1152; /* default to maximum */
+
+	if (!dlfb_parse_vendor_descriptor(dev, usbdev)) {
+		dl_err("firmware not recognized. Assume incompatible device\n");
+		goto error;
+	}
+
+	if (!dlfb_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
+		retval = -ENOMEM;
+		dl_err("dlfb_alloc_urb_list failed\n");
+		goto error;
+	}
+
+	/* We don't register a new USB class. Our client interface is fbdev */
+
+	/* allocates framebuffer driver structure, not framebuffer memory */
+	info = framebuffer_alloc(0, &usbdev->dev);
+	if (!info) {
+		retval = -ENOMEM;
+		dl_err("framebuffer_alloc failed\n");
+		goto error;
+	}
+
+	dev->info = info;
+	info->par = dev;
+	info->pseudo_palette = dev->pseudo_palette;
+	info->fbops = &dlfb_ops;
+
+	retval = fb_alloc_cmap(&info->cmap, 256, 0);
+	if (retval < 0) {
+		dl_err("fb_alloc_cmap failed %x\n", retval);
+		goto error;
+	}
+
+	INIT_DELAYED_WORK(&dev->free_framebuffer_work,
+			  dlfb_free_framebuffer_work);
+
+	INIT_LIST_HEAD(&info->modelist);
+
+	retval = dlfb_setup_modes(dev, info, NULL, 0);
+	if (retval != 0) {
+		dl_err("unable to find common mode for display and adapter\n");
+		goto error;
+	}
+
+	/* ready to begin using device */
+
+	atomic_set(&dev->usb_active, 1);
+	dlfb_select_std_channel(dev);
+
+	dlfb_ops_check_var(&info->var, info);
+	dlfb_ops_set_par(info);
+
+	retval = register_framebuffer(info);
+	if (retval < 0) {
+		dl_err("register_framebuffer failed %d\n", retval);
+		goto error;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
+		device_create_file(info->dev, &fb_device_attrs[i]);
+
+	device_create_bin_file(info->dev, &edid_attr);
+
+	dl_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."
+			" Using %dK framebuffer memory\n", info->node,
+			info->var.xres, info->var.yres,
+			((dev->backing_buffer) ?
+			info->fix.smem_len * 2 : info->fix.smem_len) >> 10);
+	return 0;
+
+error:
+	if (dev) {
+
+		if (info) {
+			if (info->cmap.len != 0)
+				fb_dealloc_cmap(&info->cmap);
+			if (info->monspecs.modedb)
+				fb_destroy_modedb(info->monspecs.modedb);
+			if (info->screen_base)
+				vfree(info->screen_base);
+
+			fb_destroy_modelist(&info->modelist);
+
+			framebuffer_release(info);
+		}
+
+		if (dev->backing_buffer)
+			vfree(dev->backing_buffer);
+
+		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
+		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */
+
+		/* dev has been deallocated. Do not dereference */
+	}
+
+	return retval;
+}
+
+static void dlfb_usb_disconnect(struct usb_interface *interface)
+{
+	struct dlfb_data *dev;
+	struct fb_info *info;
+	int i;
+
+	dev = usb_get_intfdata(interface);
+	info = dev->info;
+
+	dl_info("USB disconnect starting\n");
+
+	/* we virtualize until all fb clients release. Then we free */
+	dev->virtualized = true;
+
+	/* When non-active we'll update virtual framebuffer, but no new urbs */
+	atomic_set(&dev->usb_active, 0);
+
+	/* remove udlfb's sysfs interfaces */
+	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
+		device_remove_file(info->dev, &fb_device_attrs[i]);
+	device_remove_bin_file(info->dev, &edid_attr);
+
+	usb_set_intfdata(interface, NULL);
+
+	/* if clients still have us open, will be freed on last close */
+	if (dev->fb_count == 0)
+		schedule_delayed_work(&dev->free_framebuffer_work, 0);
+
+	/* release reference taken by kref_init in probe() */
+	kref_put(&dev->kref, dlfb_free);
+
+	/* consider dlfb_data freed */
+
+	return;
+}
+
+static struct usb_driver dlfb_driver = {
+	.name = "udlfb",
+	.probe = dlfb_usb_probe,
+	.disconnect = dlfb_usb_disconnect,
+	.id_table = id_table,
+};
+
+static int __init dlfb_module_init(void)
+{
+	int res;
+
+	res = usb_register(&dlfb_driver);
+	if (res)
+		err("usb_register failed. Error number %d", res);
+
+	return res;
+}
+
+static void __exit dlfb_module_exit(void)
+{
+	usb_deregister(&dlfb_driver);
+}
+
+module_init(dlfb_module_init);
+module_exit(dlfb_module_exit);
+
+static void dlfb_urb_completion(struct urb *urb)
+{
+	struct urb_node *unode = urb->context;
+	struct dlfb_data *dev = unode->dev;
+	unsigned long flags;
+
+	/* sync/async unlink faults aren't errors */
+	if (urb->status) {
+		if (!(urb->status == -ENOENT ||
+		    urb->status == -ECONNRESET ||
+		    urb->status == -ESHUTDOWN)) {
+			dl_err("%s - nonzero write bulk status received: %d\n",
+				__func__, urb->status);
+			atomic_set(&dev->lost_pixels, 1);
+		}
+	}
+
+	urb->transfer_buffer_length = dev->urbs.size; /* reset to actual */
+
+	spin_lock_irqsave(&dev->urbs.lock, flags);
+	list_add_tail(&unode->entry, &dev->urbs.list);
+	dev->urbs.available++;
+	spin_unlock_irqrestore(&dev->urbs.lock, flags);
+
+	/*
+	 * When using fb_defio, we deadlock if up() is called
+	 * while another is waiting. So queue to another process.
+	 */
+	if (fb_defio)
+		schedule_delayed_work(&unode->release_urb_work, 0);
+	else
+		up(&dev->urbs.limit_sem);
+}
+
+static void dlfb_free_urb_list(struct dlfb_data *dev)
+{
+	int count = dev->urbs.count;
+	struct list_head *node;
+	struct urb_node *unode;
+	struct urb *urb;
+	int ret;
+	unsigned long flags;
+
+	dl_notice("Waiting for completes and freeing all render urbs\n");
+
+	/* keep waiting and freeing, until we've got 'em all */
+	while (count--) {
+
+		/* Getting interrupted means a leak, but ok at shutdown*/
+		ret = down_interruptible(&dev->urbs.limit_sem);
+		if (ret)
+			break;
+
+		spin_lock_irqsave(&dev->urbs.lock, flags);
+
+		node = dev->urbs.list.next; /* have reserved one with sem */
+		list_del_init(node);
+
+		spin_unlock_irqrestore(&dev->urbs.lock, flags);
+
+		unode = list_entry(node, struct urb_node, entry);
+		urb = unode->urb;
+
+		/* Free each separately allocated piece */
+		usb_free_coherent(urb->dev, dev->urbs.size,
+				  urb->transfer_buffer, urb->transfer_dma);
+		usb_free_urb(urb);
+		kfree(node);
+	}
+
+}
+
+static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
+{
+	int i = 0;
+	struct urb *urb;
+	struct urb_node *unode;
+	char *buf;
+
+	spin_lock_init(&dev->urbs.lock);
+
+	dev->urbs.size = size;
+	INIT_LIST_HEAD(&dev->urbs.list);
+
+	while (i < count) {
+		unode = kzalloc(sizeof(struct urb_node), GFP_KERNEL);
+		if (!unode)
+			break;
+		unode->dev = dev;
+
+		INIT_DELAYED_WORK(&unode->release_urb_work,
+			  dlfb_release_urb_work);
+
+		urb = usb_alloc_urb(0, GFP_KERNEL);
+		if (!urb) {
+			kfree(unode);
+			break;
+		}
+		unode->urb = urb;
+
+		buf = usb_alloc_coherent(dev->udev, MAX_TRANSFER, GFP_KERNEL,
+					 &urb->transfer_dma);
+		if (!buf) {
+			kfree(unode);
+			usb_free_urb(urb);
+			break;
+		}
+
+		/* urb->transfer_buffer_length set to actual before submit */
+		usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 1),
+			buf, size, dlfb_urb_completion, unode);
+		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+
+		list_add_tail(&unode->entry, &dev->urbs.list);
+
+		i++;
+	}
+
+	sema_init(&dev->urbs.limit_sem, i);
+	dev->urbs.count = i;
+	dev->urbs.available = i;
+
+	dl_notice("allocated %d %d byte urbs\n", i, (int) size);
+
+	return i;
+}
+
+static struct urb *dlfb_get_urb(struct dlfb_data *dev)
+{
+	int ret = 0;
+	struct list_head *entry;
+	struct urb_node *unode;
+	struct urb *urb = NULL;
+	unsigned long flags;
+
+	/* Wait for an in-flight buffer to complete and get re-queued */
+	ret = down_timeout(&dev->urbs.limit_sem, GET_URB_TIMEOUT);
+	if (ret) {
+		atomic_set(&dev->lost_pixels, 1);
+		dl_warn("wait for urb interrupted: %x available: %d\n",
+		       ret, dev->urbs.available);
+		goto error;
+	}
+
+	spin_lock_irqsave(&dev->urbs.lock, flags);
+
+	BUG_ON(list_empty(&dev->urbs.list)); /* reserved one with limit_sem */
+	entry = dev->urbs.list.next;
+	list_del_init(entry);
+	dev->urbs.available--;
+
+	spin_unlock_irqrestore(&dev->urbs.lock, flags);
+
+	unode = list_entry(entry, struct urb_node, entry);
+	urb = unode->urb;
+
+error:
+	return urb;
+}
+
+static int dlfb_submit_urb(struct dlfb_data *dev, struct urb *urb, size_t len)
+{
+	int ret;
+
+	BUG_ON(len > dev->urbs.size);
+
+	urb->transfer_buffer_length = len; /* set to actual payload len */
+	ret = usb_submit_urb(urb, GFP_KERNEL);
+	if (ret) {
+		dlfb_urb_completion(urb); /* because no one else will */
+		atomic_set(&dev->lost_pixels, 1);
+		dl_err("usb_submit_urb error %x\n", ret);
+	}
+	return ret;
+}
+
+module_param(console, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
+MODULE_PARM_DESC(console, "Allow fbcon to consume first framebuffer found");
+
+module_param(fb_defio, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
+MODULE_PARM_DESC(fb_defio, "Enable fb_defio mmap support. *Experimental*");
+
+MODULE_AUTHOR("Roberto De Ioris <roberto@unbit.it>, "
+	      "Jaya Kumar <jayakumar.lkml@gmail.com>, "
+	      "Bernie Thompson <bernie@plugable.com>");
+MODULE_DESCRIPTION("DisplayLink kernel framebuffer driver");
+MODULE_LICENSE("GPL");
+
diff --git a/include/video/udlfb.h b/include/video/udlfb.h
new file mode 100644
index 000000000000..6f9785e9d62e
--- /dev/null
+++ b/include/video/udlfb.h
@@ -0,0 +1,117 @@
+#ifndef UDLFB_H
+#define UDLFB_H
+
+/*
+ * TODO: Propose standard fb.h ioctl for reporting damage,
+ * using _IOWR() and one of the existing area structs from fb.h
+ * Consider these ioctls deprecated, but they're still used by the
+ * DisplayLink X server as yet - need both to be modified in tandem
+ * when new ioctl(s) are ready.
+ */
+#define DLFB_IOCTL_RETURN_EDID	 0xAD
+#define DLFB_IOCTL_REPORT_DAMAGE 0xAA
+struct dloarea {
+	int x, y;
+	int w, h;
+	int x2, y2;
+};
+
+struct urb_node {
+	struct list_head entry;
+	struct dlfb_data *dev;
+	struct delayed_work release_urb_work;
+	struct urb *urb;
+};
+
+struct urb_list {
+	struct list_head list;
+	spinlock_t lock;
+	struct semaphore limit_sem;
+	int available;
+	int count;
+	size_t size;
+};
+
+struct dlfb_data {
+	struct usb_device *udev;
+	struct device *gdev; /* &udev->dev */
+	struct fb_info *info;
+	struct urb_list urbs;
+	struct kref kref;
+	char *backing_buffer;
+	int fb_count;
+	bool virtualized; /* true when physical usb device not present */
+	struct delayed_work free_framebuffer_work;
+	atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */
+	atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */
+	char *edid; /* null until we read edid from hw or get from sysfs */
+	size_t edid_size;
+	int sku_pixel_limit;
+	int base16;
+	int base8;
+	u32 pseudo_palette[256];
+	/* blit-only rendering path metrics, exposed through sysfs */
+	atomic_t bytes_rendered; /* raw pixel-bytes driver asked to render */
+	atomic_t bytes_identical; /* saved effort with backbuffer comparison */
+	atomic_t bytes_sent; /* to usb, after compression including overhead */
+	atomic_t cpu_kcycles_used; /* transpired during pixel processing */
+};
+
+#define NR_USB_REQUEST_I2C_SUB_IO 0x02
+#define NR_USB_REQUEST_CHANNEL 0x12
+
+/* -BULK_SIZE as per usb-skeleton. Can we get full page and avoid overhead? */
+#define BULK_SIZE 512
+#define MAX_TRANSFER (PAGE_SIZE*16 - BULK_SIZE)
+#define WRITES_IN_FLIGHT (4)
+
+#define MIN_EDID_SIZE 128
+#define MAX_EDID_SIZE 128
+
+#define MAX_VENDOR_DESCRIPTOR_SIZE 256
+
+#define GET_URB_TIMEOUT	HZ
+#define FREE_URB_TIMEOUT (HZ*2)
+
+#define BPP                     2
+#define MAX_CMD_PIXELS		255
+
+#define RLX_HEADER_BYTES	7
+#define MIN_RLX_PIX_BYTES       4
+#define MIN_RLX_CMD_BYTES	(RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
+
+#define RLE_HEADER_BYTES	6
+#define MIN_RLE_PIX_BYTES	3
+#define MIN_RLE_CMD_BYTES	(RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
+
+#define RAW_HEADER_BYTES	6
+#define MIN_RAW_PIX_BYTES	2
+#define MIN_RAW_CMD_BYTES	(RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
+
+#define DL_DEFIO_WRITE_DELAY    5 /* fb_deferred_io.delay in jiffies */
+#define DL_DEFIO_WRITE_DISABLE  (HZ*60) /* "disable" with long delay */
+
+/* remove these once align.h patch is taken into kernel */
+#define DL_ALIGN_UP(x, a) ALIGN(x, a)
+#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
+
+/* remove once this gets added to sysfs.h */
+#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
+
+/*
+ * udlfb is both a usb device, and a framebuffer device.
+ * They may exist at the same time, but during various stages
+ * inactivity, teardown, or "virtual" operation, only one or the
+ * other will exist (one will outlive the other).  So we can't
+ * call the dev_*() macros, because we don't have a stable dev object.
+ */
+#define dl_err(format, arg...) \
+	pr_err("udlfb: " format, ## arg)
+#define dl_warn(format, arg...) \
+	pr_warning("udlfb: " format, ## arg)
+#define dl_notice(format, arg...) \
+	pr_notice("udlfb: " format, ## arg)
+#define dl_info(format, arg...) \
+	pr_info("udlfb: " format, ## arg)
+
+#endif