[PATCH 07/32] acpi-video-detect: Rewrite backlight interface selection logic

Pali Rohár pali.rohar at gmail.com
Thu Jun 11 02:19:22 PDT 2015

On Wednesday 10 June 2015 15:01:07 Hans de Goede wrote:
> Currently we have 2 kernel commandline options + dmi-quirks in 3 places all
> interacting (in interesting ways) to select which which backlight interface
> to use. On the commandline we've acpi_backlight=[video|vendor] and
> video.use_native_backlight=[0|1]. DMI quirks we have in
> acpi/video-detect.c, acpi/video.c and drivers/platform/x86/*.c .
> This commit is the first step to cleaning this up, replacing the 2 cmdline
> options with just acpi_video.backlight=[video|vendor|native|none], and
> adding a new API to video_detect.c to reflect this.
> Follow up commits will also move other related code, like unregistering the
> acpi_video backlight interface if it was registered before other drivers
> which take priority over it are loaded, to video_detect.c where this
> logic really belongs.
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>


lot of people are using acpi_backlight parameter in kernel cmdline to
fix some of problems. I would like to see this parameter still working
and to not break existing configuration. E.g acpi_backlight=vendor to
use dell-laptop.ko or thinkpad_acpi.ko backlight.

It is still nightmare to get laptop panel backlight working on different
(broken) laptops and people learnt to try to use acpi_backlight
parameter for quit/hot fixing these problems. Upgrading kernel (if you
remove acpi_backlight parameter) just break it again.

Pali Rohár
pali.rohar at gmail.com

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