2 * Simple synchronous userspace interface to SPI devices
4 * Copyright (C) 2006 SWAPP
5 * Andrea Paterniani <a.paterniani@swapp-eng.it>
6 * Copyright (C) 2007 David Brownell (simplification, cleanup)
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/ioctl.h>
27 #include <linux/device.h>
28 #include <linux/err.h>
29 #include <linux/list.h>
30 #include <linux/errno.h>
31 #include <linux/mutex.h>
32 #include <linux/slab.h>
33 #include <linux/compat.h>
35 #include <linux/of_device.h>
37 #include <linux/spi/spi.h>
38 #include <linux/spi/spidev.h>
40 #include <asm/uaccess.h>
44 * This supports access to SPI devices using normal userspace I/O calls.
45 * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
46 * and often mask message boundaries, full SPI support requires full duplex
47 * transfers. There are several kinds of internal message boundaries to
48 * handle chipselect management and other protocol options.
50 * SPI has a character major number assigned. We allocate minor numbers
51 * dynamically using a bitmask. You must use hotplug tools, such as udev
52 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
53 * nodes, since there is no fixed association of minor numbers with any
54 * particular SPI bus or device.
56 #define SPIDEV_MAJOR 153 /* assigned */
57 #define N_SPI_MINORS 32 /* ... up to 256 */
59 static DECLARE_BITMAP(minors, N_SPI_MINORS);
62 /* Bit masks for spi_device.mode management. Note that incorrect
63 * settings for some settings can cause *lots* of trouble for other
64 * devices on a shared bus:
66 * - CS_HIGH ... this device will be active when it shouldn't be
67 * - 3WIRE ... when active, it won't behave as it should
68 * - NO_CS ... there will be no explicit message boundaries; this
69 * is completely incompatible with the shared bus model
70 * - READY ... transfers may proceed when they shouldn't.
72 * REVISIT should changing those flags be privileged?
74 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
75 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
76 | SPI_NO_CS | SPI_READY)
81 struct spi_device *spi;
82 struct list_head device_entry;
84 /* buffer is NULL unless this device is open (users > 0) */
85 struct mutex buf_lock;
90 static LIST_HEAD(device_list);
91 static DEFINE_MUTEX(device_list_lock);
93 static unsigned bufsiz = 4096;
94 module_param(bufsiz, uint, S_IRUGO);
95 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
97 /*-------------------------------------------------------------------------*/
100 * We can't use the standard synchronous wrappers for file I/O; we
101 * need to protect against async removal of the underlying spi_device.
103 static void spidev_complete(void *arg)
109 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
111 DECLARE_COMPLETION_ONSTACK(done);
114 message->complete = spidev_complete;
115 message->context = &done;
117 spin_lock_irq(&spidev->spi_lock);
118 if (spidev->spi == NULL)
121 status = spi_async(spidev->spi, message);
122 spin_unlock_irq(&spidev->spi_lock);
125 wait_for_completion(&done);
126 status = message->status;
128 status = message->actual_length;
133 static inline ssize_t
134 spidev_sync_write(struct spidev_data *spidev, size_t len)
136 struct spi_transfer t = {
137 .tx_buf = spidev->buffer,
140 struct spi_message m;
142 spi_message_init(&m);
143 spi_message_add_tail(&t, &m);
144 return spidev_sync(spidev, &m);
147 static inline ssize_t
148 spidev_sync_read(struct spidev_data *spidev, size_t len)
150 struct spi_transfer t = {
151 .rx_buf = spidev->buffer,
154 struct spi_message m;
156 spi_message_init(&m);
157 spi_message_add_tail(&t, &m);
158 return spidev_sync(spidev, &m);
161 /*-------------------------------------------------------------------------*/
163 /* Read-only message with current device setup */
165 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
167 struct spidev_data *spidev;
170 /* chipselect only toggles at start or end of operation */
174 spidev = filp->private_data;
176 mutex_lock(&spidev->buf_lock);
177 status = spidev_sync_read(spidev, count);
179 unsigned long missing;
181 missing = copy_to_user(buf, spidev->buffer, status);
182 if (missing == status)
185 status = status - missing;
187 mutex_unlock(&spidev->buf_lock);
192 /* Write-only message with current device setup */
194 spidev_write(struct file *filp, const char __user *buf,
195 size_t count, loff_t *f_pos)
197 struct spidev_data *spidev;
199 unsigned long missing;
201 /* chipselect only toggles at start or end of operation */
205 spidev = filp->private_data;
207 mutex_lock(&spidev->buf_lock);
208 missing = copy_from_user(spidev->buffer, buf, count);
210 status = spidev_sync_write(spidev, count);
213 mutex_unlock(&spidev->buf_lock);
218 static int spidev_message(struct spidev_data *spidev,
219 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
221 struct spi_message msg;
222 struct spi_transfer *k_xfers;
223 struct spi_transfer *k_tmp;
224 struct spi_ioc_transfer *u_tmp;
227 int status = -EFAULT;
229 spi_message_init(&msg);
230 k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
234 /* Construct spi_message, copying any tx data to bounce buffer.
235 * We walk the array of user-provided transfers, using each one
236 * to initialize a kernel version of the same transfer.
238 buf = spidev->buffer;
240 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
242 n--, k_tmp++, u_tmp++) {
243 k_tmp->len = u_tmp->len;
246 /* Check total length of transfers. Also check each
247 * transfer length to avoid arithmetic overflow.
249 if (total > bufsiz || k_tmp->len > bufsiz) {
256 if (!access_ok(VERIFY_WRITE, (u8 __user *)
257 (uintptr_t) u_tmp->rx_buf,
263 if (copy_from_user(buf, (const u8 __user *)
264 (uintptr_t) u_tmp->tx_buf,
270 k_tmp->cs_change = !!u_tmp->cs_change;
271 k_tmp->bits_per_word = u_tmp->bits_per_word;
272 k_tmp->delay_usecs = u_tmp->delay_usecs;
273 k_tmp->speed_hz = u_tmp->speed_hz;
275 dev_dbg(&spidev->spi->dev,
276 " xfer len %zd %s%s%s%dbits %u usec %uHz\n",
278 u_tmp->rx_buf ? "rx " : "",
279 u_tmp->tx_buf ? "tx " : "",
280 u_tmp->cs_change ? "cs " : "",
281 u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
283 u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
285 spi_message_add_tail(k_tmp, &msg);
288 status = spidev_sync(spidev, &msg);
292 /* copy any rx data out of bounce buffer */
293 buf = spidev->buffer;
294 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
296 if (__copy_to_user((u8 __user *)
297 (uintptr_t) u_tmp->rx_buf, buf,
313 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
317 struct spidev_data *spidev;
318 struct spi_device *spi;
321 struct spi_ioc_transfer *ioc;
323 /* Check type and command number */
324 if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
327 /* Check access direction once here; don't repeat below.
328 * IOC_DIR is from the user perspective, while access_ok is
329 * from the kernel perspective; so they look reversed.
331 if (_IOC_DIR(cmd) & _IOC_READ)
332 err = !access_ok(VERIFY_WRITE,
333 (void __user *)arg, _IOC_SIZE(cmd));
334 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
335 err = !access_ok(VERIFY_READ,
336 (void __user *)arg, _IOC_SIZE(cmd));
340 /* guard against device removal before, or while,
341 * we issue this ioctl.
343 spidev = filp->private_data;
344 spin_lock_irq(&spidev->spi_lock);
345 spi = spi_dev_get(spidev->spi);
346 spin_unlock_irq(&spidev->spi_lock);
351 /* use the buffer lock here for triple duty:
352 * - prevent I/O (from us) so calling spi_setup() is safe;
353 * - prevent concurrent SPI_IOC_WR_* from morphing
354 * data fields while SPI_IOC_RD_* reads them;
355 * - SPI_IOC_MESSAGE needs the buffer locked "normally".
357 mutex_lock(&spidev->buf_lock);
361 case SPI_IOC_RD_MODE:
362 retval = __put_user(spi->mode & SPI_MODE_MASK,
365 case SPI_IOC_RD_LSB_FIRST:
366 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0,
369 case SPI_IOC_RD_BITS_PER_WORD:
370 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
372 case SPI_IOC_RD_MAX_SPEED_HZ:
373 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
377 case SPI_IOC_WR_MODE:
378 retval = __get_user(tmp, (u8 __user *)arg);
382 if (tmp & ~SPI_MODE_MASK) {
387 tmp |= spi->mode & ~SPI_MODE_MASK;
389 retval = spi_setup(spi);
393 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
396 case SPI_IOC_WR_LSB_FIRST:
397 retval = __get_user(tmp, (__u8 __user *)arg);
402 spi->mode |= SPI_LSB_FIRST;
404 spi->mode &= ~SPI_LSB_FIRST;
405 retval = spi_setup(spi);
409 dev_dbg(&spi->dev, "%csb first\n",
413 case SPI_IOC_WR_BITS_PER_WORD:
414 retval = __get_user(tmp, (__u8 __user *)arg);
416 u8 save = spi->bits_per_word;
418 spi->bits_per_word = tmp;
419 retval = spi_setup(spi);
421 spi->bits_per_word = save;
423 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
426 case SPI_IOC_WR_MAX_SPEED_HZ:
427 retval = __get_user(tmp, (__u32 __user *)arg);
429 u32 save = spi->max_speed_hz;
431 spi->max_speed_hz = tmp;
432 retval = spi_setup(spi);
434 spi->max_speed_hz = save;
436 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
441 /* segmented and/or full-duplex I/O request */
442 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
443 || _IOC_DIR(cmd) != _IOC_WRITE) {
448 tmp = _IOC_SIZE(cmd);
449 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
453 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
457 /* copy into scratch area */
458 ioc = kmalloc(tmp, GFP_KERNEL);
463 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
469 /* translate to spi_message, execute */
470 retval = spidev_message(spidev, ioc, n_ioc);
475 mutex_unlock(&spidev->buf_lock);
482 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
484 return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
487 #define spidev_compat_ioctl NULL
488 #endif /* CONFIG_COMPAT */
490 static int spidev_open(struct inode *inode, struct file *filp)
492 struct spidev_data *spidev;
495 mutex_lock(&device_list_lock);
497 list_for_each_entry(spidev, &device_list, device_entry) {
498 if (spidev->devt == inode->i_rdev) {
504 if (!spidev->buffer) {
505 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
506 if (!spidev->buffer) {
507 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
513 filp->private_data = spidev;
514 nonseekable_open(inode, filp);
517 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
519 mutex_unlock(&device_list_lock);
523 static int spidev_release(struct inode *inode, struct file *filp)
525 struct spidev_data *spidev;
528 mutex_lock(&device_list_lock);
529 spidev = filp->private_data;
530 filp->private_data = NULL;
534 if (!spidev->users) {
537 kfree(spidev->buffer);
538 spidev->buffer = NULL;
540 /* ... after we unbound from the underlying device? */
541 spin_lock_irq(&spidev->spi_lock);
542 dofree = (spidev->spi == NULL);
543 spin_unlock_irq(&spidev->spi_lock);
548 mutex_unlock(&device_list_lock);
553 static const struct file_operations spidev_fops = {
554 .owner = THIS_MODULE,
555 /* REVISIT switch to aio primitives, so that userspace
556 * gets more complete API coverage. It'll simplify things
557 * too, except for the locking.
559 .write = spidev_write,
561 .unlocked_ioctl = spidev_ioctl,
562 .compat_ioctl = spidev_compat_ioctl,
564 .release = spidev_release,
568 /*-------------------------------------------------------------------------*/
570 /* The main reason to have this class is to make mdev/udev create the
571 * /dev/spidevB.C character device nodes exposing our userspace API.
572 * It also simplifies memory management.
575 static struct class *spidev_class;
577 /*-------------------------------------------------------------------------*/
579 static int spidev_probe(struct spi_device *spi)
581 struct spidev_data *spidev;
585 /* Allocate driver data */
586 spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
590 /* Initialize the driver data */
592 spin_lock_init(&spidev->spi_lock);
593 mutex_init(&spidev->buf_lock);
595 INIT_LIST_HEAD(&spidev->device_entry);
597 /* If we can allocate a minor number, hook up this device.
598 * Reusing minors is fine so long as udev or mdev is working.
600 mutex_lock(&device_list_lock);
601 minor = find_first_zero_bit(minors, N_SPI_MINORS);
602 if (minor < N_SPI_MINORS) {
605 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
606 dev = device_create(spidev_class, &spi->dev, spidev->devt,
607 spidev, "spidev%d.%d",
608 spi->master->bus_num, spi->chip_select);
609 status = PTR_RET(dev);
611 dev_dbg(&spi->dev, "no minor number available!\n");
615 set_bit(minor, minors);
616 list_add(&spidev->device_entry, &device_list);
618 mutex_unlock(&device_list_lock);
621 spi_set_drvdata(spi, spidev);
628 static int spidev_remove(struct spi_device *spi)
630 struct spidev_data *spidev = spi_get_drvdata(spi);
632 /* make sure ops on existing fds can abort cleanly */
633 spin_lock_irq(&spidev->spi_lock);
635 spi_set_drvdata(spi, NULL);
636 spin_unlock_irq(&spidev->spi_lock);
638 /* prevent new opens */
639 mutex_lock(&device_list_lock);
640 list_del(&spidev->device_entry);
641 device_destroy(spidev_class, spidev->devt);
642 clear_bit(MINOR(spidev->devt), minors);
643 if (spidev->users == 0)
645 mutex_unlock(&device_list_lock);
650 static const struct of_device_id spidev_dt_ids[] = {
651 { .compatible = "rohm,dh2228fv" },
655 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
657 static struct spi_driver spidev_spi_driver = {
660 .owner = THIS_MODULE,
661 .of_match_table = of_match_ptr(spidev_dt_ids),
663 .probe = spidev_probe,
664 .remove = spidev_remove,
666 /* NOTE: suspend/resume methods are not necessary here.
667 * We don't do anything except pass the requests to/from
668 * the underlying controller. The refrigerator handles
669 * most issues; the controller driver handles the rest.
673 /*-------------------------------------------------------------------------*/
675 static int __init spidev_init(void)
679 /* Claim our 256 reserved device numbers. Then register a class
680 * that will key udev/mdev to add/remove /dev nodes. Last, register
681 * the driver which manages those device numbers.
683 BUILD_BUG_ON(N_SPI_MINORS > 256);
684 status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
688 spidev_class = class_create(THIS_MODULE, "spidev");
689 if (IS_ERR(spidev_class)) {
690 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
691 return PTR_ERR(spidev_class);
694 status = spi_register_driver(&spidev_spi_driver);
696 class_destroy(spidev_class);
697 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
701 module_init(spidev_init);
703 static void __exit spidev_exit(void)
705 spi_unregister_driver(&spidev_spi_driver);
706 class_destroy(spidev_class);
707 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
709 module_exit(spidev_exit);
711 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
712 MODULE_DESCRIPTION("User mode SPI device interface");
713 MODULE_LICENSE("GPL");
714 MODULE_ALIAS("spi:spidev");