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authorHans de Goede <hdegoede@redhat.com>2022-11-04 18:06:29 +0100
committerHans de Goede <hdegoede@redhat.com>2022-11-07 12:33:20 +0100
commit454d61a56d5e4c8cd9905f81d475d23f86f370af (patch)
tree3c46b407199b54ff4e514f025dff3ec1d94a7b0e /drivers/acpi/video_detect.c
parentACPI: video: Improve Chromebook checks (diff)
downloadlinux-454d61a56d5e4c8cd9905f81d475d23f86f370af.tar.xz
linux-454d61a56d5e4c8cd9905f81d475d23f86f370af.zip
ACPI: video: Make acpi_video_backlight_use_native() always return true
Testing has shown that there are quite a few laptop models which rely on native backlight control and which do not support ACPI video bus backlight control, causing __acpi_video_get_backlight_type() to return vendor. Known Windows laptop models affected by this are: Acer Aspire 1640 HP Compaq nc6120 IBM ThinkPad X40 System76 Starling Star1 and the following MacBook models are affected too: Apple MacBook 2.1 Apple MacBook 4.1 Apple MacBook Pro 7.1 the list of affected Windows laptop models is likely just the top of the iceberg. So for now lets undo the change to not register native backlight class devices when __acpi_video_get_backlight_type() != native. Since as part of the backlight-detect refactor the detection code now relies on the GPU drivers calling acpi_video_backlight_use_native() to learn that native backlight support is available we cannot just remove the acpi_video_backlight_use_native() calls from the GPU drivers. Instead modify acpi_video_backlight_use_native() to always return true for now. This is meant as a temporary work-around, which will be removed again when the heuristics from __acpi_video_get_backlight_type() have been improved so that they will return native on affected models. Reported-by: Matthew Garrett <mjg59@srcf.ucam.org> Reported-by: John Warriner <taijitu@cox.net> Reported-by: Scott Ostrander <sos12_3@hotmail.com> Reported-by: Matthias Rampke <matthias.rampke@googlemail.com> Reported-by: Milan Hodoscek <hmilan@gmail.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Diffstat (limited to '')
-rw-r--r--drivers/acpi/video_detect.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 06aaec2e378b..c02e960cdbe3 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -751,6 +751,18 @@ EXPORT_SYMBOL(acpi_video_get_backlight_type);
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);