[systemd-devel] systemd backlight:acpi_video0 fails, no such device

[Mantas Mikulėnas]

On Mon, Sep 2, 2019 at 7:34 AM Chris Murphy <lists at colorremedies.com> wrote:

> systemd-243~rc2-2.fc31.x86_64
> kernel-5.3.0-0.rc6.git1.1.fc32.x86_64
>
> This might be a regression, at least I don't remember this happening
> before. I can use the expected keys for built-in display brightness,
> and built-in keyboard brightness. But the service unit fails with an
> out of the box installation.
>
>
> [chris at fmac ~]$ sudo systemctl status
> systemd-backlight at backlight:acpi_video0.service
> ● systemd-backlight at backlight:acpi_video0.service - Load/Save Screen
> Backlight Brightness of backlight:acpi_video0
>    Loaded: loaded (/usr/lib/systemd/system/systemd-backlight at .service;
> static; vendor preset: disabled)
>    Active: failed (Result: exit-code) since Sun 2019-09-01 19:57:37
> MDT; 8min ago
>      Docs: man:systemd-backlight at .service(8)
>   Process: 667 ExecStart=/usr/lib/systemd/systemd-backlight load
> backlight:acpi_video0 (code=exited, status=1/FAILURE)
>  Main PID: 667 (code=exited, status=1/FAILURE)
>
> Sep 01 19:57:37 fmac.local systemd[1]: Starting Load/Save Screen
> Backlight Brightness of backlight:acpi_video0...
> Sep 01 19:57:37 fmac.local systemd-backlight[667]: Failed to get
> backlight or LED device 'backlight:acpi_video0': No such device
> Sep 01 19:57:37 fmac.local systemd[1]:
> systemd-backlight at backlight:acpi_video0.service: Main process exited,
> code=exited, status=1/FAILURE
> Sep 01 19:57:37 fmac.local systemd[1]:
> systemd-backlight at backlight:acpi_video0.service: Failed with result
> 'exit-code'.
> Sep 01 19:57:37 fmac.local systemd[1]: Failed to start Load/Save
> Screen Backlight Brightness of backlight:acpi_video0.
> [chris at fmac ~]$
>
> # find /sys -name "*video0*"
> /sys/class/video4linux/video0
> /sys/devices/pci0000:00/0000:00:1a.7/usb1/1-2/1-2:1.0/video4linux/video0
> # ls -l /sys/class/backlight/
> total 0
> lrwxrwxrwx. 1 root root 0 Sep  1 19:57 gmux_backlight ->
> ../../devices/pnp0/00:03/backlight/gmux_backlight
> lrwxrwxrwx. 1 root root 0 Sep  1 19:57 intel_backlight ->
>
> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
>

Could it be that acpi_backlight is loaded at first, but gets replaced by
intel_backlight before systemd could react?

-- 
Mantas Mikulėnas
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