Bug 4183 - Backlight/Brightness hotkeys (Fn+F2 and Fn+F3) not work on Samsung NP-N100
: Backlight/Brightness hotkeys (Fn+F2 and Fn+F3) not work on Samsung NP-N100
Status: RESOLVED NOTABUG
Product: Desktop Bugs
Classification: ROSA Desktop
Component: LXDE Edition
: Fresh
: All Linux
: Normal normal
: ---
Assigned To: Eugene Shatokhin
: ROSA Linux Bugs
:
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2014-07-01 23:51 MSD by Eugene Budanov
Modified: 2014-07-08 17:34 MSD (History)
2 users (show)

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Attachments
Full log (1.21 MB, application/octet-stream)
2014-07-01 23:51 MSD, Eugene Budanov
Details

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Description Eugene Budanov 2014-07-01 23:51:00 MSD
Created attachment 3022 [details]
Full log

On Samsung netbook not working hotkeys for changing brighntess level by pressing Fn+F keys.

journalctl -f output when pressing buttons:

Jul 02 00:06:41 netbook systemd-udevd[391]: specified group 'scanner' unknown
Jul 02 00:07:13 netbook systemd-udevd[391]: specified group 'scanner' unknown
Jul 02 00:07:17 netbook systemd-udevd[391]: specified group 'scanner' unknown
Jul 02 00:07:21 netbook systemd-udevd[391]: specified group 'scanner' unknown
Jul 02 00:07:24 netbook systemd-udevd[391]: specified group 'scanner' unknown
Jul 02 00:07:27 netbook systemd-udevd[391]: specified group 'scanner' unknown

Full journalctl -a log is attached too.
Comment 1 Eugene Budanov 2014-07-03 00:17:17 MSD
[root@netbook ~]# showkey --keycodes
kb mode was ?UNKNOWN?
[ if you are trying this under X, it might not work
since the X server is also reading /dev/console ]

press any key (program terminates 10s after last keypress)...
keycode  28 release
keycode 224 press
keycode 224 release
keycode 224 press
keycode 224 release
keycode 224 press
keycode 224 release
keycode 224 press
keycode 224 release
keycode 225 press
keycode 225 release
keycode 225 press
keycode 225 release
keycode 225 press
keycode 225 release
keycode 225 press
keycode 225 release

Four times was pressed Fn+F2 and then Fn+F3.

[root@netbook ~]# showkey --scancodes
kb mode was ?UNKNOWN?
[ if you are trying this under X, it might not work
since the X server is also reading /dev/console ]

press any key (program terminates 10s after last keypress)...
0x9c 
0xe0 0x4c 0xe0 0xcc 
0xe0 0x4c 0xe0 0xcc 
0xe0 0x4c 0xe0 0xcc 
0xe0 0x4c 0xe0 0xcc 
0xe0 0x54 0xe0 0xd4 
0xe0 0x54 0xe0 0xd4 
0xe0 0x54 0xe0 0xd4 
0xe0 0x54 0xe0 0xd4
Comment 2 Eugene Shatokhin 2014-07-08 16:51:14 MSD
Long story short: use 'acpi_backlight=vendor' kernel parameter (set it in /etc/default/grub to make it persistent) and everything should work on this laptop.

I checked that the keys are mapped correctly. The problem was, there are two subsystems that might control brightness, see /sys/class/backlight/.

intel_backlight works, acpi0_backlight does not. And Samsung-specific backlight controls are not even present here. By default the system does not use vendor-specific backlight controls. If I instruct it to use these (with 'acpi_backlight=vendor' kernel parameter at boot), the keys controlling brightness work OK.
Comment 3 Vladimir Potapov 2014-07-08 17:01:21 MSD
(In reply to comment #2)
> Long story short: use 'acpi_backlight=vendor' kernel parameter (set it in
> /etc/default/grub to make it persistent) and everything should work on this
> laptop.
> 
> I checked that the keys are mapped correctly. The problem was, there are two
> subsystems that might control brightness, see /sys/class/backlight/.
> 
> intel_backlight works, acpi0_backlight does not. And Samsung-specific
> backlight controls are not even present here. By default the system does not
> use vendor-specific backlight controls. If I instruct it to use these (with
> 'acpi_backlight=vendor' kernel parameter at boot), the keys controlling
> brightness work OK.

Please, write the message to errata.
Comment 4 Eugene Shatokhin 2014-07-08 17:34:25 MSD
> Please, write the message to errata.

Done.