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ACPI: video: Prefer native over vendor

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When available prefer native backlight control over vendor backlight
control.

Testing has shown that there are quite a few laptop models which rely
on native backlight control (they don't have ACPI video bus backlight
control) and on which acpi_osi_is_win8() returns false.

Currently __acpi_video_get_backlight_type() returns vendor on these
laptops, leading to an empty /sys/class/backlight.

As a workaround for this acpi_video_backlight_use_native() has been
temporarily changed to always return true.

This re-introduces the problem of having multiple backlight
devices under /sys/class/backlight for a single panel.

Change __acpi_video_get_backlight_type() to prefer native over vendor
when available. So that it returns native on these models.

And change acpi_video_backlight_use_native() back to only return
true when __acpi_video_get_backlight_type() returns native.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Hans de Goede 2022-11-14 15:44:59 +01:00 • committed by Rafael J. Wysocki
parent a5df42521f
commit fb1836c913
1 changed files with 3 additions and 15 deletions
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18
drivers/acpi/video_detect.c
View file

@ -776,10 +776,10 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
return acpi_backlight_video; return acpi_backlight_video;
/* Use native if available */ /* Use native if available */
if (native_available && prefer_native_over_acpi_video()) if (native_available)
return acpi_backlight_native; return acpi_backlight_native;
/* No ACPI video (old hw), use vendor specific fw methods. */ /* No ACPI video/native (old hw), use vendor specific fw methods. */
return acpi_backlight_vendor; return acpi_backlight_vendor;
} }
@ -791,18 +791,6 @@ EXPORT_SYMBOL(acpi_video_get_backlight_type);
bool acpi_video_backlight_use_native(void) bool acpi_video_backlight_use_native(void)
{ {
/* return __acpi_video_get_backlight_type(true) == acpi_backlight_native;
* Call __acpi_video_get_backlight_type() to let it know that
* a native backlight is available.
*/
__acpi_video_get_backlight_type(true);
/*
* For now just always return true. There is a whole bunch of laptop
* models where (video_caps & ACPI_VIDEO_BACKLIGHT) is false causing
* __acpi_video_get_backlight_type() to return vendor, while these
* models only have a native backlight control.
*/
return true;
} }
EXPORT_SYMBOL(acpi_video_backlight_use_native); EXPORT_SYMBOL(acpi_video_backlight_use_native);