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ACPI: video: Make acpi_backlight=video work independent from GPU driver 

Commit 3dbc80a3e4 ("ACPI: video: Make backlight class device
registration a separate step (v2)") combined with
commit 5aa9d943e9 ("ACPI: video: Don't enable fallback path for
creating ACPI backlight by default")

Means that the video.ko code now fully depends on the GPU driver calling
acpi_video_register_backlight() for the acpi_video# backlight class
devices to get registered.

This means that if the GPU driver does not do this, acpi_backlight=video
on the cmdline, or DMI quirks for selecting acpi_video# will not work.

This is a problem on for example Apple iMac14,1 all-in-ones where
the monitor's LCD panel shows up as a regular DP connection instead of
eDP so the GPU driver will not call acpi_video_register_backlight() [1].

Fix this by making video.ko directly register the acpi_video# devices
when these have been explicitly requested either on the cmdline or
through DMI quirks (rather then auto-detection being used).

[1] GPU drivers only call acpi_video_register_backlight() when an internal
panel is detected, to avoid non working acpi_video# devices getting
registered on desktops which unfortunately is a real issue.

Fixes: 5aa9d943e9 ("ACPI: video: Don't enable fallback path for creating ACPI backlight by default")
Cc: All applicable <stable@vger.kernel.org>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
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 2023-04-04 13:02:47 +02:00 committed by Rafael J. Wysocki
parent 78dfc9d1d1
commit e506731c8f
1 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/acpi/acpi_video.c
View File

@ -1984,6 +1984,7 @@ static int instance;
static int acpi_video_bus_add(struct acpi_device *device)
{
struct acpi_video_bus *video;
bool auto_detect;
int error;
acpi_status status;
@ -2045,10 +2046,20 @@ static int acpi_video_bus_add(struct acpi_device *device)
mutex_unlock(&video_list_lock);
/*
* The userspace visible backlight_device gets registered separately
* from acpi_video_register_backlight().
* If backlight-type auto-detection is used then a native backlight may
* show up later and this may change the result from video to native.
* Therefor normally the userspace visible /sys/class/backlight device
* gets registered separately by the GPU driver calling
* acpi_video_register_backlight() when an internal panel is detected.
* Register the backlight now when not using auto-detection, so that
* when the kernel cmdline or DMI-quirks are used the backlight will
* get registered even if acpi_video_register_backlight() is not called.
*/
acpi_video_run_bcl_for_osi(video);
if (__acpi_video_get_backlight_type(false, &auto_detect) == acpi_backlight_video &&
!auto_detect)
acpi_video_bus_register_backlight(video);
acpi_video_bus_add_notify_handler(video);
return 0;