[Bug 214899] ideapad-laptop: brightness hotkeys not working

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=214899

--- Comment #22 from Hans de Goede (jwrdegoede@fedoraproject.org) ---
Sorry for the slow reply (note I'm afraid my next reply will likely also be a
bit slow).

Good find on the methods, so this means that the key-press events are supposed
to come from the "Video Bus" device and as you point out for some reason this
is not happening. I guess that the drivers/acpi/acpi_video.c is not making some
call to enable the events which your laptop requires; or it is making a call
which it should not make which disables the events...

One thing which I just noticed is that when passing acpi_backlight=video you
get 2 acpi_video# backlight devices. Given that AFAICT your laptop has only a
single GPU,  may be an indication of a problem.

I wonder what happens when you pass:

video.only_lcd=1 acpi_backlight=video

on the kernel cmdline, I would expect there to only be 1 acpi_video# backlight
device under /sys/class/backlight then ?    And maybe this also fixes the
brightness keys?

I assume that without any "acpi_backlight=xxx" on the kernel cmdline you only
get the intel_backlight device, right? You could also check to see if adding
just "video.only_lcd=1" to the kernel cmdline helps.

If that does not help, you may want to play with the acpi_video_bus_DOS() call
from 
drivers/acpi/acpi_video.c .

This gets called from the acpi_video_bus_start_devices() function:

static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
{
        return acpi_video_bus_DOS(video, 0,
                                  acpi_osi_is_win8() ? 1 : 0);
}

You may want to modify this trying the following:

        return acpi_video_bus_DOS(video, 3,
                                  acpi_osi_is_win8() ? 1 : 0);

Looking at your acpidump it seems the second parameter is ignored, so changing
that will likely not matter.

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