From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Subject: Re: [PATCH 2/4] drm/i915: prevent tiling changes on
 framebuffer backing storage
Date: Thu, 10 Oct 2013 13:53:53 +0300
Message-ID: <20131010105353.GK13047@intel.com>
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To: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>
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On Thu, Oct 10, 2013 at 12:09:48AM +0200, Daniel Vetter wrote:
> On Thu, Oct 10, 2013 at 12:02:17AM +0200, Daniel Vetter wrote:
> > On Wed, Oct 09, 2013 at 10:29:39PM +0100, Chris Wilson wrote:
> > > On Wed, Oct 09, 2013 at 09:23:52PM +0200, Daniel Vetter wrote:
> > > > Assuming that all framebuffer related metadata is invariant simplif=
ies
> > > > our userspace input data checking. And current userspace always fir=
st
> > > > updates the tiling of an object before creating a framebuffer with =
it.
> > > =

> > > Userspace already changes the tiling layout whilst keeping the fb id.
> > =

> > How exactly does that work? You can't really change the fb pitch without
> > creating a new one ... That leaves switching from tiled to untiled and
> > back I think.
> =

> Meh, didn't read sna carefully enough. On a second read we only seem to
> have the code added
> =

> commit 0dd20381364aabede2e1306945abe21d57c1d7b4
> Author: Chris Wilson <chris@chris-wilson.co.uk>
> Date:   Sun Sep 29 11:19:46 2013 +0100
> =

>     sna: Resize an existing framebuffer if possible
> =

> That seems to just be for the cache, should be able to cope with failures
> and we can fix it by moving the rmfb up before the set_tiling. It's also
> only 2 weeks old.
> =

> So if there's nothing else I've missed I strongly vote to break the
> pre-release over saner intefaces - allowing tiling to change kinda wreaks
> a bit havoc with out in-kernel checks ...

It would be a bit simpler if we can trust that things don't change
after we've created the fb.

-- =

Ville Syrj=E4l=E4
Intel OTC