Re: [Intel-gfx] [PATCH v3 7/7] drm: Allow drivers to leave encoder->possible_crtcs==0

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org,
	Thierry Reding <treding@nvidia.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH v3 7/7] drm: Allow drivers to leave encoder->possible_crtcs==0
Date: Wed, 18 Mar 2020 18:44:52 +0200	[thread overview]
Message-ID: <20200318164452.GB13686@intel.com> (raw)
In-Reply-To: <20200212090849.GQ2363188@phenom.ffwll.local>

On Wed, Feb 12, 2020 at 10:08:49AM +0100, Daniel Vetter wrote:
> On Wed, Feb 12, 2020 at 10:07:55AM +0100, Daniel Vetter wrote:
> > On Tue, Feb 11, 2020 at 07:14:51PM +0200, Ville Syrjälä wrote:
> > > On Tue, Feb 11, 2020 at 06:05:45PM +0100, Daniel Vetter wrote:
> > > > On Tue, Feb 11, 2020 at 06:22:08PM +0200, Ville Syrjala wrote:
> > > > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > > 
> > > > > Let's simplify life of driver by allowing them to leave
> > > > > encoder->possible_crtcs unset if they have no restrictions
> > > > > in crtc<->encoder linkage. We'll just populate possible_crtcs
> > > > > with the full crtc mask when registering the encoder so that
> > > > > userspace doesn't have to deal with drivers not populating
> > > > > this correctly.
> > > > > 
> > > > > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > > > > Cc: Daniel Vetter <daniel@ffwll.ch>
> > > > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > > ---
> > > > > We might not actually need/want this, but included it here for
> > > > > future reference if that assumption turns out to be wrong.
> > > > 
> > > > I think this one is most definitely needed. _Lots_ of drivers get this
> > > > toally wrong and just leave the value blank. It's encoded as official
> > > > fallback in most userspace compositors.
> > > 
> > > OK. It's been a while since I dug around so can't really remmber how
> > > this was being handled. I'll reorder before pushing.
> > 
> > Hm otoh having "works with all crtcs" as default is a bit dangerous,
> > whereas the "cannot be cloned" default for possible_clones is perfectly
> > safe.
> > 
> > So now I'm kinda not sure whether this is a bright idea, and we shouldn't
> > just eat the cost of fixing up all the various WARNING backtraces your
> > previous patch triggers. I've done a full review and the following look
> > suspect:
> > 
> > - tegara/sor.c Strangely it's the only one, the other output drivers do
> >   seem to set the possible_crtcs mask to something useful.
> 
> Strike that, it sets it using tegra_output_find_possible_crtcs().
> 
> I think everything is good and we really don't need this patch here to fix
> up possible_crtcs.

Finally pushed the other patches from the series to drm-misc-next.
Thanks for the reviews.

Should the new possible_{crtcs,clones} WARNs start to trigger for
anyone despite our best efforts, please holler and I'll look into
what needs fixing.

-- 
Ville Syrjälä
Intel
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