ACPI / i915: ignore firmware requests for backlight change

Some Thinkpad laptops' firmware will initiate a backlight level change
request through operation region on the events of AC plug/unplug, but
since we are not using firmware's interface to do the backlight setting
on these affected laptops, we do not want the firmware to use some
arbitrary value from its ASL variable to set the backlight level on
AC plug/unplug either.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=76491
Link: https://bugzilla.kernel.org/show_bug.cgi?id=77091
Reported-and-tested-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
Reported-and-tested-by: Anton Gubarkov <anton.gubarkov@gmail.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index fb9ffe9adc645601361092c7252778a1aacf2e43..5bb1278e93243a16421fd21e158a6025e8f145e7 100644 (file)
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -241,13 +241,14 @@ static bool acpi_video_use_native_backlight(void)
                return use_native_backlight_dmi;
 }
 
-static bool acpi_video_verify_backlight_support(void)
+bool acpi_video_verify_backlight_support(void)
 {
        if (acpi_osi_is_win8() && acpi_video_use_native_backlight() &&
            backlight_device_registered(BACKLIGHT_RAW))
                return false;
        return acpi_video_backlight_support();
 }
+EXPORT_SYMBOL_GPL(acpi_video_verify_backlight_support);
 
 /* backlight device sysfs support */
 static int acpi_video_get_brightness(struct backlight_device *bd)

diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 2e2c71fcc9ed502dc3a013089d53a3270999ad51..4f6b53998d79652dafca7ea7e7f609a1d35eaca6 100644 (file)
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -403,6 +403,15 @@ static u32 asle_set_backlight(struct drm_device *dev, u32 bclp)
 
        DRM_DEBUG_DRIVER("bclp = 0x%08x\n", bclp);
 
+       /*
+        * If the acpi_video interface is not supposed to be used, don't
+        * bother processing backlight level change requests from firmware.
+        */
+       if (!acpi_video_verify_backlight_support()) {
+               DRM_DEBUG_KMS("opregion backlight request ignored\n");
+               return 0;
+       }
+
        if (!(bclp & ASLE_BCLP_VALID))
                return ASLC_BACKLIGHT_FAILED;
 

diff --git a/include/acpi/video.h b/include/acpi/video.h
index ea4c7bbded4d3c5841cf3819dbe2ed1a4871d265..843ef1adfbfab7ca736055f2333e2af8413ba7ef 100644 (file)
--- a/include/acpi/video.h
+++ b/include/acpi/video.h
@@ -22,6 +22,7 @@ extern void acpi_video_unregister(void);
 extern void acpi_video_unregister_backlight(void);
 extern int acpi_video_get_edid(struct acpi_device *device, int type,
                               int device_id, void **edid);
+extern bool acpi_video_verify_backlight_support(void);
 #else
 static inline int acpi_video_register(void) { return 0; }
 static inline void acpi_video_unregister(void) { return; }
@@ -31,6 +32,7 @@ static inline int acpi_video_get_edid(struct acpi_device *device, int type,
 {
        return -ENODEV;
 }
+static inline bool acpi_video_verify_backlight_support(void) { return false; }
 #endif
 
 #endif