Re: [PATCH] drm/i915/opregion: ignore firmware requests for backlight change

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 24 Jun 2014, Aaron Lu <aaron.lu@intel.com> wrote:
> 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.

I'm curious whether this happens with EFI boot, or only with legacy.

One comment inline, otherwise

Acked-by: Jani Nikula <jani.nikula@intel.com>

for merging through the ACPI tree, as the change is more likely to
conflict there.

> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=76491
> Buglink: 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>
> ---
>  drivers/acpi/video.c                  | 3 ++-
>  drivers/gpu/drm/i915/intel_opregion.c | 7 +++++++
>  include/acpi/video.h                  | 2 ++
>  3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index fb9ffe9adc64..cf99d6d2d491 100644
> --- 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(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 2e2c71fcc9ed..02943d93e88e 100644
> --- a/drivers/gpu/drm/i915/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/intel_opregion.c
> @@ -403,6 +403,13 @@ 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())
> +		return 0;

I'd appreciate a DRM_DEBUG_KMS here about what happened. We're bound to
wonder about that staring at some dmesg later on!

> +
>  	if (!(bclp & ASLE_BCLP_VALID))
>  		return ASLC_BACKLIGHT_FAILED;
>  
> diff --git a/include/acpi/video.h b/include/acpi/video.h
> index ea4c7bbded4d..92f8c4bffefb 100644
> --- 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 bool acpi_video_verify_backlight_support() { return false; }
>  #endif
>  
>  #endif
> -- 
> 1.9.3
>

-- 
Jani Nikula, Intel Open Source Technology Center