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

[Josh Triplett]

On Wed, Mar 05, 2014 at 06:59:27PM +0100, David Herrmann wrote:
> 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.

Likewise.

> > - 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).

Perhaps this will get fixed when we switch from kernel VTs to a
userspace-managed console, then.

- Josh Triplett