[Mesa-dev] [PATCH] [rfc] dri3: allow building against older xcb

[Emil Velikov]

Hi Dave,

On 11 March 2018 at 23:26, Dave Airlie <airlied at gmail.com> wrote:
> From: Dave Airlie <airlied at redhat.com>
>
> I'm not sure everyone wants to be updating their dri3 in a forced
> march setting, this allows a nicer approach, esp when you want
> to build on distro that aren't brand new.
>
> I'm sure there are plenty of ways this patch could be cleaner,
> and I've also not built it against an updated dri3.

Have you considered cases where the build server is using 1.12, while
at run-time we have 1.13?
Are you explicitly forbidding that, say via the packaging? It tends to
be allowed on most(all?) distributions.

FWIW I'd recommend updating XCB since apart from the features, it
addresses some nasty issues in the Vulkan drivers [1].

That said, if updating XCB is a serious no-go, may I suggest something
like the following:
 - add local fallback definitions/declarations
 - add local functions (annotated as weak) which return 'the correct'
value so that the fallback paths kick in

HTH
Emil

[1] https://cgit.freedesktop.org/xcb/libxcb/commit/?id=fad81b63422105f9345215ab2716c4b804ec7986