linux-kernel - Re: [PATCH 3/3] drm/vc4: Add support for dma-buf fencing.

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Date:   Tue, 11 Apr 2017 10:43:35 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo.padovan@...labora.com>
Subject: Re: [PATCH 3/3] drm/vc4: Add support for dma-buf fencing.

Chris Wilson <chris@...is-wilson.co.uk> writes:

> On Mon, Apr 10, 2017 at 06:44:14PM -0700, Eric Anholt wrote:
>> This is needed for proper synchronization with display on another DRM
>> device (pl111 or tinydrm) with buffers produced by vc4 V3D.  Fixes the
>> new igt vc4_dmabuf_poll testcase, and rendering of one of the glmark2
>> desktop tests on pl111+vc4.
>> 
>> This doesn't yet introduce waits on other device's fences before vc4's
>> rendering/display, because I don't have testcases for them.
>> 
>> Signed-off-by: Eric Anholt <eric@...olt.net>
>> Cc: Gustavo Padovan <gustavo.padovan@...labora.com>
>> ---
>> +static void vc4_fence_release(struct dma_fence *fence)
>> +{
>> +	struct vc4_fence *f = to_vc4_fence(fence);
>> +
>> +	kfree_rcu(f, base.rcu);
>> +}
>
> Unless you have a plan to do more here, looks like you can just use
> the default dma_fence_free as the release callback.
> -Chris

Yeah, this pattern came from etnaviv/msm (which I had used as
reference), who both put their .base second.  I wonder if they would
want to flip the order of their fields and drop their fence_release,
too.

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