Re: [Intel-gfx] [PATCH 3/5] drm/i915: Update CRTC state if connector link status property changed

From: Manasi Navare <manasi.d.navare@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Daniel Vetter <daniel@ffwll.ch>,
	dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 3/5] drm/i915: Update CRTC state if connector link status property changed
Date: Mon, 21 Nov 2016 13:07:47 -0800	[thread overview]
Message-ID: <20161121210746.GA25494@intel.com> (raw)
In-Reply-To: <20161121204619.GA8188@nuc-i3427.alporthouse.com>

On Mon, Nov 21, 2016 at 08:46:19PM +0000, Chris Wilson wrote:
> On Mon, Nov 21, 2016 at 11:00:52AM -0800, Manasi Navare wrote:
> > On Mon, Nov 21, 2016 at 04:48:07PM +0100, Daniel Vetter wrote:
> > > On Mon, Nov 21, 2016 at 11:10:45AM +0100, Daniel Vetter wrote:
> > > > On Mon, Nov 21, 2016 at 09:42:57AM +0000, Chris Wilson wrote:
> > > > > On Mon, Nov 21, 2016 at 10:38:20AM +0100, Daniel Vetter wrote:
> > > > > > - Another fallout is that legacy clients will no longer see the
> > > > > >   link-status property. And they won't be able to set it through the
> > > > > >   SETCRTC ioctl, which would kinda defaut the point. I think the best
> > > > > >   solution would be to check for link_status == BAD in
> > > > > >   drm_atomic_helper_set_config, and reset it to good automatically for
> > > > > >   legacy clients.
> > > > > 
> > > > > Then how do they know that the kernel demands the modeset? Both a legacy
> > > > > and atomic property?
> > > > 
> > > > I guess we could avoid the filtering of the property for legacy clients.
> > > > Definitely not 2 properties, that's silly. Or we teach userspace to go
> > > > look for atomic properties.
> > > 
> > > Well, now that I flushed the gunk out of my brain with some work-out it's
> > > a lot easier: ATOMIC on properties is only to hide them from legacy
> > > userspace, it doesn't control how it's implement. Which means we can
> > > implement it as described above, and non-atomic userspace can still read
> > > it. Setting would also work, but since we want to do that as part of
> > > SETCRTC anyway, and since legacy SETCRTC doesn't specifiy whether a
> > > modeset will happen or not, automagic in there seems reasonable.
> > 
> > Thanks Daniel for providing the solution alternatives here.
> > So after we make it atomic, we would solve the problem of updating the connector_changed
> > in atomic_helper_check_modeset function. So in this, who resets the property to GOOD?
> > Would this happen in drm_atomic_helper_set_config in both atomic and non atomic cases?
> > 
> > And in case of non atomic userspace, will it still be able to read link-status as BAD in userspace
> > to decide whether it needs to call setcrtc?
> > 
> > Chris, will any implementation in your patch for link _status change if this is made atomic?
> 
> So long at the property remains visible via the GETCONNECTOR ioctl, no.
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

If it is made an atomic property, will it be visible to userspace through
GETCONNECTOR?

Manasi
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