Commit 2600bfa3 authored by Hans de Goede's avatar Hans de Goede
Browse files

ACPI: video: Add acpi_video_backlight_use_native() helper 



ATM on x86 laptops where we want userspace to use the acpi_video backlight
device we often register both the GPU's native backlight device and
acpi_video's firmware acpi_video# backlight device. This relies on
userspace preferring firmware type backlight devices over native ones, but
registering 2 backlight devices for a single display really is undesirable.

On x86 laptops where the native GPU backlight device should be used,
the registering of other backlight devices is avoided by their drivers
using acpi_video_get_backlight_type() and only registering their backlight
if the return value matches their type.

acpi_video_get_backlight_type() uses
backlight_device_get_by_type(BACKLIGHT_RAW) to determine if a native
driver is available and will never return native if this returns
false. This means that the GPU's native backlight registering code
cannot just call acpi_video_get_backlight_type() to determine if it
should register its backlight, since acpi_video_get_backlight_type() will
never return native until the native backlight has already registered.

To fix this add a new internal native function parameter to
acpi_video_get_backlight_type(), which when set to true will make
acpi_video_get_backlight_type() behave as if a native backlight has
already been registered.

And add a new acpi_video_backlight_use_native() helper, which sets this
to true, for use in native GPU backlight code.

Changes in v2:
- Replace adding a native parameter to acpi_video_get_backlight_type() with
  adding a new acpi_video_backlight_use_native() helper.

Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
parent 568035b0

drivers/acpi/video_detect.c

+20 −4
Original line number Diff line number Diff line
@@ -17,8 +17,9 @@ 
 * Otherwise vendor specific drivers like thinkpad_acpi, asus-laptop,

 * sony_acpi,... can take care about backlight brightness.

 *

 * Backlight drivers can use acpi_video_get_backlight_type() to determine

 * which driver should handle the backlight.

 * Backlight drivers can use acpi_video_get_backlight_type() to determine which

 * driver should handle the backlight. RAW/GPU-driver backlight drivers must

 * use the acpi_video_backlight_use_native() helper for this.

 *

 * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)

 * this file will not be compiled and acpi_video_get_backlight_type() will
@@ -571,9 +572,10 @@ static int acpi_video_backlight_notify(struct notifier_block *nb, 
 * Arguably the native on win8 check should be done first, but that would

 * be a behavior change, which may causes issues.

 */

enum acpi_backlight_type acpi_video_get_backlight_type(void)

static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)

{

	static DEFINE_MUTEX(init_mutex);

	static bool native_available;

	static bool init_done;

	static long video_caps;
@@ -593,6 +595,8 @@ enum acpi_backlight_type acpi_video_get_backlight_type(void) 
			backlight_notifier_registered = true;

		init_done = true;

	}

	if (native)

		native_available = true;

	mutex_unlock(&init_mutex);



	if (acpi_backlight_cmdline != acpi_backlight_undef)
@@ -604,13 +608,25 @@ enum acpi_backlight_type acpi_video_get_backlight_type(void) 
	if (!(video_caps & ACPI_VIDEO_BACKLIGHT))

		return acpi_backlight_vendor;



	if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))

	if (acpi_osi_is_win8() &&

	    (native_available || backlight_device_get_by_type(BACKLIGHT_RAW)))

		return acpi_backlight_native;



	return acpi_backlight_video;

}



enum acpi_backlight_type acpi_video_get_backlight_type(void)

{

	return __acpi_video_get_backlight_type(false);

}

EXPORT_SYMBOL(acpi_video_get_backlight_type);



bool acpi_video_backlight_use_native(void)

{

	return __acpi_video_get_backlight_type(true) == acpi_backlight_native;

}

EXPORT_SYMBOL(acpi_video_backlight_use_native);



/*

 * Set the preferred backlight interface type based on DMI info.

 * This function allows DMI blacklists to be implemented by external

include/acpi/video.h

+5 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ extern void acpi_video_unregister(void); 
extern int acpi_video_get_edid(struct acpi_device *device, int type,

			       int device_id, void **edid);

extern enum acpi_backlight_type acpi_video_get_backlight_type(void);

extern bool acpi_video_backlight_use_native(void);

extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);

/*

 * Note: The value returned by acpi_video_handles_brightness_key_presses()
@@ -77,6 +78,10 @@ static inline enum acpi_backlight_type acpi_video_get_backlight_type(void) 
{

	return acpi_backlight_vendor;

}

static inline bool acpi_video_backlight_use_native(void)

{

	return true;

}

static inline void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)

{

}