[Intel-gfx] drm i915 weirdness with /sys/class/drm/card0*/status

[Chris Wilson]

On Tue, Jun 16, 2015 at 11:28:19PM +0200, Lennart Poettering wrote:
> On Tue, 16.06.15 12:37, Chris Wilson (chris at chris-wilson.co.uk) wrote:
> 
> > On Tue, Jun 16, 2015 at 01:17:29PM +0200, Lennart Poettering wrote:
> > > On Tue, 16.06.15 10:14, Chris Wilson (chris at chris-wilson.co.uk) wrote:
> > > 
> > > > The biggest change here is 4.1 stopped forcing the probe from sysfs
> > > > precisely because systemd was hitting them so often for illogical
> > > > reasons (being docked depends on having the lid open and an
> > > > external display connected!). To force the probe, you must do
> > > > 	$ echo detect > /sys/class/drm/*/status
> > > 
> > > The way people "dock" their laptops these days is apparently that
> > > they plug in an external keyboard+mouse and a display, close the lid
> > > and stash the laptop away somewhere. logind hence counts the displays
> > > connected, and if its >= 2 it doesn't suspend the machine even if the
> > > lid is closed. Before logind, GNOME implemented the very same
> > > logic. It's hence hardly "illogical", it's just how this works...
> > 
> > Note that a closed lid causes the internal panel to be reported as
> > disconnected - it always has (with the exception of a module parameter
> > to force otherwise to accommodate broken lid buttons). Using the number
> > of connected displays is thus flawed.
> 
> Hmm, if I change the algorithm to ignore the eDP and LVDS outputs and
> see if any of the others is plugged + enabled should fix this, correct?

LVDS/eDP/DSI/MIPI + more unknown

Though even VGA/DVI have turned up in some systems to drive panels.

On a working i915 system, if there is any display connected, it means
the lid is either open or there a cable plugged in. Respond too quickly
to a hotunplug event though and you may end up suspending due to an
interrupt storm or just a single failed EDID read.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre