[systemd-devel] systemd-backlight and backlight level 0

[David Herrmann]

Hi

On Wed, Mar 5, 2014 at 6:46 PM, Josh Triplett <josh at joshtriplett.org> wrote:
> systemd-backlight saves backlight levels on shutdown, and restores them
> on startup.  However, on some systems, backlight level 0 actually turns
> the backlight *off*; this can potentially make the system unusable.
> Complicating matters, on most systems, nothing pays attention to the
> brightness adjustment keys in text mode.
>
> I'd suggest one or both of the following two changes, to avoid a painful
> failure mode:
>
> - systemd-backlight should avoid saving/restoring a backlight level of
>   0, and have a minimum backlight level.  (Possibly overridable via
>   configuration, for people who *really* want to restore backlight level
>   0.)

Never restoring val==0 seems fine to me.

> - Something ought to listen to the brightness keys (and perhaps other
>   hotkeys) in pure text mode.  systemd seems like a good place for such
>   a something to live.

We cannot do that. It requires keymap-handling (as brightness keys are
handled on the keysym, not keycode level) and this is exclusive
territory of the compositor (or other foreground session controllers).

Thanks
David