[Intel-gfx] [PATCH 1/2] drm: Add a new connector property for link status

[Ville Syrjälä]

On Wed, Oct 26, 2016 at 02:11:00PM +0100, Chris Wilson wrote:
> On Wed, Oct 26, 2016 at 02:17:16PM +0300, Ville Syrjälä wrote:
> > On Wed, Oct 26, 2016 at 12:51:41PM +0300, Jani Nikula wrote:
> > > On Wed, 26 Oct 2016, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > > > On Wed, Oct 26, 2016 at 07:52:26AM +0200, Daniel Vetter wrote:
> > > >> I'd go further and just always create this as one of the standard
> > > >> properties (and always attach it to the connector, like edid), and only
> > > >> expose helpers to set the link status to good or bad.
> > > >
> > > > One of the sketches for this idea was that this could serve as the
> > > > failure notification path for nonblocking modesets (well modesets in
> > > > general since it appears returning the error is not going to happen).
> > > 
> > > In nonblocking modesets, when should we change the status from bad to
> > > good? If the setcrtc returns and userspace looks at link status and sees
> > > it's still bad (because the kernel hasn't gotten around to enabling the
> > > link yet, or whatever), userspace might think it would have to try
> > > again. Do we set it to good immediately on setcrtc ioctl, or add a
> > > "pending" status? Or something better?
> > 
> > I was thinking it'd start out as "good" and only change to something
> > else when things actually go south.
> > 
> > Not sure if we should also want "off" as one of the values, for when
> > it's really off at the request of the user.
> 
> That's something the user knows. At least, if the ddx has output->crtc
> set and sees that link-status=off the response is to say "that can't be
> me!" and reapply the desired mode, i.e. same response as if the
> link-status was bad. Maybe useful for someone else to differentiate?

Dunno really. If we don't add it we have to define what the link status
will indicate when the thing is really off though. With "good" and "bad"
the only options I guess "good" would be the right answer?

-- 
Ville Syrjälä
Intel OTC