[PATCH 09/12] Do more checks for proposed flip pixmaps

Keith Packard keithp at keithp.com
Wed Jul 30 23:01:48 PDT 2014

Eric Anholt <eric at anholt.net> writes:

> Keith Packard <keithp at keithp.com> writes:
>> Make sure the pitch and tiling are correct.
>> Make sure there's a BO we can get at.
> I thought we couldn't change these parameters, but now I can't find what
> prevents them from changing.  Can you cite sources?

Looks like we *can* change tiling format. That actually makes me kinda
happy as that explains why we were able to allocate a linear frame
buffer for the X front buffer (due to a bug) and page flip to DRI3
buffers which are always tiled.

However, we can't change the pitch. From the kernel driver:

	 * TILEOFF/LINOFF registers can't be changed via MI display flips.
	 * Note that pitch changes could also affect these register.
	if (INTEL_INFO(dev)->gen > 3 &&
	    (fb->offsets[0] != crtc->primary->fb->offsets[0] ||
	     fb->pitches[0] != crtc->primary->fb->pitches[0]))
		return -EINVAL;

I'll remove the tiling check.

keith.packard at intel.com
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