Re: [Mesa-dev] Implement GLX_EXT_buffer_age for DRI2

From: Daniel Stone <daniel@fooishbar.org>
To: Dave Airlie <airlied@gmail.com>
Cc: "mesa-dev@lists.freedesktop.org" <mesa-dev@lists.freedesktop.org>,
	"xorg-devel@lists.x.org" <xorg-devel@lists.x.org>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [Mesa-dev] Implement GLX_EXT_buffer_age for DRI2
Date: Wed, 18 Feb 2015 18:40:05 +0000	[thread overview]
Message-ID: <CAPj87rMbJn9tS-s+cXkZrMgSL_gvUWegpCZSBWZpC7SXj9ibvA@mail.gmail.com> (raw)
In-Reply-To: <CAPM=9txQBFK5=L2+_5TA8RQv+bex6OCBXfJjVEfDwAgkotKPqA@mail.gmail.com>

Hi,

On 20 January 2015 at 21:49, Dave Airlie <airlied@gmail.com> wrote:
> On 19 January 2015 at 21:00, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>> In order to suport GLX_EXT_buffer_age in DRI2, we need to pass back the
>> last swap buffer count that the back buffer was defined for. For
>> simplicity, we can reuse an existing field in the DRI2GetBuffers reply
>> that is not used by current drivers, the flags. Since we change the
>> interpretation of this flag, we also declare the semantic change with a
>> DRI2 parameter and depend upon the DDX to enable the change
>> responsibility (which is just a matter of reviewing whether the flags
>> field has ever been used for a non-zero value).
>
> This is just missing the why do we need to add this to DRI2 when we
> have DRI3/Present that should be solving it.
>
> Doesn't dri3 already do this?

DRI3/Present still seem to be pretty unstable and break a bunch of
stuff, and buffer_age is definitely a useful optimisation for non-TBDR
platforms, so I don't see why not.

Cheers,
Daniel
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