[Intel-gfx] [PATCH 3/6] drm/i915: Support write only mappings

[Keith Packard]

On Mon, 19 Sep 2011 21:25:03 -0700, Ben Widawsky <ben at bwidawsk.net> wrote:
> When doing a GTT mapping, the pages are not backed until taking a fault.
> If we know that the object is write only, when the fault happens we do not need
> to make the pages coherent with the CPU.  This allows for semi fast prefaults
> to occur in libdrm at map time.

Every time I see this stuff, I get confused by the term
'write-only'. Reading through the code, I remind myself that what you're
actually promising is that any CPU accesses to the object will not
overlap any potential writes by the GPU. The CPU could be reading or
writing, it really doesn't matter.

Really what you want is a kernel call that does everything except block
on the GPU, right?

-- 
keith.packard at intel.com
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