[PATCH 1/3] drm/arm: hdlcd: properly validate plane state

[Liviu Dudau]

On Fri, Mar 31, 2017 at 11:27:51AM +0100, Russell King - ARM Linux wrote:
> On Fri, Mar 31, 2017 at 11:23:45AM +0100, Liviu Dudau wrote:
> > On Fri, Mar 31, 2017 at 11:20:35AM +0100, Russell King - ARM Linux wrote:
> > > On Fri, Mar 31, 2017 at 11:18:50AM +0100, Liviu Dudau wrote:
> > > > Hi Russell,
> > > > 
> > > > You were Cc-ed in a patch from March 8th that did all this:
> > > > 
> > > > https://lists.freedesktop.org/archives/dri-devel/2017-March/135172.html
> > > 
> > > I'm aware of that (you may notice that this was threaded to that patch.)
> > > 
> > > > I have not received any response from you, so I have already pushed the
> > > > patch in my public repo:
> > > > 
> > > > git://linux-arm.org/linux-ld.git for-upstream/hdlcd
> > > > 
> > > > It has been included into linux-next for at least a couple of weeks now.
> > > 
> > > I've not had a chance to test any of this, but I believe that your
> > > patch does not fully address the issue, due to bits missing from
> > > the validation path.
> > 
> > Care to point out which bits were missing from my patch that are in yours?
> 
> The visible check?

A plane's ->atomic_check() hook can be called with TEST_ONLY to figure out from
userspace if the given configuration is a valid one that can be accepted by
the hardware. There should be no error if the plane will not be visible, as we
are not programming anything yet.

I would also argue that the test that you remove and replace with state->visible
is important. We can't do *any* scaling, while with your patch we could accept
src_w != crtc_w as long as it is visible. Hardware is not capable of handling that.

Best regards,
Liviu

> 
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