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

[bugzilla-daemon@kernel.org]

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

--- Comment #23 from Johannes P (johannes.penssel@gmail.com) ---
No problem, this isn't exactly the most pressing of issues.

Looks like neither any combination of kernel parameters, nor the code change
you suggested, leads to any difference in behaviour.

My laptop does have a 2nd GPU actually, a GeForce MX450 which is for all
practical purposes disabled at runtime by the nouveau driver. But no matter if
enabled or disabled in BIOS, there is only the intel_backlight device in sysfs
without any kernel parameters, as expected. By the way, enabling the GPU
results in this warning message at boot:

[    3.894320] ACPI: video: [Firmware Bug]: ACPI(PEGP) defines _DOD but not
_DOS

Interestingly, I have noticed that booting with acpi_backlight=video results in
just one acpi_video device appearing in sysfs now. (regardless if the GPU is
activated or not) I'm not sure if this is due to a change in BIOS or the
kernel, so just to be sure, I am uploading an acpi dump from the most recent
BIOS release. 

Here is some additional info about the input devices registered by acpi video
that might be helpful:

/proc/bus/input/devices

I: Bus=0019 Vendor=0000 Product=0006 Version=0000
N: Name="Video Bus"
P: Phys=LNXVIDEO/video/input0
S:
Sysfs=/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:00/LNXVIDEO:00/input/input8
U: Uniq=
H: Handlers=kbd event6 
B: PROP=0
B: EV=3
B: KEY=3e000b00000000 0 0 0

I: Bus=0019 Vendor=0000 Product=0006 Version=0000
N: Name="Video Bus"
P: Phys=LNXVIDEO/video/input0
S: Sysfs=/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:01/input/input9
U: Uniq=
H: Handlers=kbd event7 
B: PROP=0
B: EV=3
B: KEY=3e000b00000000 0 0 0

Not sure if relevant, but something else I have noticed is that the brightness
value recorded by the ideapad backlight device, which as mentioned does change
when the brightness keys are pressed, corresponds to value B9 on the register
map dumped by the kernel ec tool:

     00  01  02  03  04  05  06  07  08  09  0A  0B  0C  0D  0E  0F
00:  00  01  00  00  00  00  00  01  00  00  10  00  00  00  29  00 
10:  00  00  80  00  01  00  65  04  00  01  9a  20  00  02  00  00 
20:  02  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00 
30:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00 
40:  00  00  00  00  00  00  00  00  00  00  00  00  8d  52  00  00 
50:  00  00  00  33  00  00  2d  00  00  00  00  00  00  00  00  00 
60:  00  80  02  03  02  00  00  08  ef  17  85  43  01  00  20  01 
70:  00  02  10  01  00  00  00  00  00  00  00  00  00  00  00  00 
80:  00  00  00  00  08  00  00  00  c0  00  93  00  20  01  00  4c 
90:  47  43  00  32  30  31  39  00  4c  31  39  4c  34  50  46  31 
A0:  00  01  00  80  00  00  c0  00  00  00  00  00  00  15  00  00 
B0:  2d  2f  00  2a  00  24  00  28  02  11  04  00  00  00  01  00 
C0:  30  00  ce  14  33  05  97  3e  10  3b  58  1b  9b  1b  4b  00 
D0:  00  00  00  00  00  00  00  23  2f  0c  00  00  00  00  00  00 
E0:  00  00  00  00  00  00  00  00  00  00  00  00  01  00  43  00 
F0:  01  00  00  40  90  51  80  43  00  00  00  00  00  00  00  00

This value persists across reboots, but does not change when pressing the
brightness keys in Windows.

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