From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 09/10] drm/i915: wait render timeout ioctl
Date: Sun, 22 Apr 2012 10:37:23 +0100
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To: Ben Widawsky <ben@bwidawsk.net>
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On Sat, 21 Apr 2012 09:12:17 -0700, Ben Widawsky <ben@bwidawsk.net> wrote:
> On Sat, 21 Apr 2012 10:41:55 +0100
> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > I think this whole interface is a stop-gap solution for pollable sync
> > objects without a clear use case. Do we have a spec for a feature
> > wishing to build upon this interface?
> 
> Good point. This is primarily for glClientWaitSync. I will update the
> commit message with this information.

I read through the ARB_sync spec and this interface does seem to be a
good match for that. A slight sour test from that spec being open-ended
which might mean that we need to revise the interface in future.
However, I did realise one blindingly obvious use-case:

  drm_intel_gem_bo_wait_wait_rendering();

Currently this is used by Mesa to do its client throttling, and in
consequence also blocks X. i915_wait_ioctl() will allow mesa to only
block itself and so help reduce interface stutters, even more important
with multiple GL clients.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre