[Piglit] New piglit/waffle with older X server

Paul Berry stereotype441 at gmail.com
Wed Feb 20 13:18:28 PST 2013

On 20 February 2013 12:26, Carl Worth <cworth at cworth.org> wrote:

> I recently ran into a bunch of piglit tests not getting run, (returning
> "skip"), when they used to work fine. The tests say things like:
>         piglit: info: Failed to create GL 2.0 compatibility context
>         piglit: info: Failed to create any GL context
> I tracked the failure down via gdb to the following line of code in
> waffle (glx_config.c):
>             if (attrs->context_full_version != 10 &&
> !dpy->ARB_create_context) {
>                 wcore_errorf(WAFFLE_ERROR_UNSUPPORTED_ON_PLATFORM,
>                              "GLX_ARB_create_context is required in order
> to "
>                              "request a GL version not equal to the
> default "
>                              "value 1.0");
>                 return false;
>             }
> In my case, attrs->context_full_version is 20.
> When I asked about this in IRC, Eric helped me out a bit:
>         <anholt> cworth: your x server is old, and piglit/waffle don't
>         fall back to just making an old context and seeing if it's good
>         enough.
> I'll go ahead and upgrade my X server so I can get things running again,
> but I'm left with the following questions:
>   1. I'm curious what's the new thing required in the X server here?
>      I'm obviously running tests that worked previously, so I'm not
>      really needing any new behavior. So this looks like a regression in
>      piglit/waffle.

What's changed was my Piglit patch "shader_runner and glslparsertest:
choose GL version more accurately", which caused Piglit to request a GL 2.1
context when running certin GLSL 1.20 tests where it previously requested a
1.0 context.  We're currently discussing what to do about that in the email
thread of the same name (see
http://lists.freedesktop.org/archives/piglit/2013-February/004949.html for
where the discussion started).

Eric has argued that we shouldn't require a GL 2.1 context when running
GLSL 1.20 tests, because sometimes Mesa supports a version of GLSL higher
than is required by the supported GL version.  I was initially skeptical
about this but I may be coming around.

>   2. Assuming this is a bug, should the missing fallback code be added
>      to piglit or to waffle?

Personally, I think so, regardless of what we decide to do about
"shader_runner and glslparsertest: choose GL version more accurately".
Piglit tests that require GL 2.1 should be able to run on any GL
2.1-supporting platform, regardless of whether that platform supports
ARB_create_context.  Especially since a lot of people are still running
Fedora 17, which doesn't have ARB_create_context X server support yet.

>   3. If waffle, Chad do you have a bug tracker set up for waffle? If
>      not, shall we add a component to bugs.freedesktop.org?
>   4. If we don't add automatic fallback code, is there some logical
>      place that we could put a better error message in place? It was not
>      at all obvious to me from "failed to create context" that my X
>      server had suddenly gotten too old, (when it worked previously).
> -Carl

FYI, Michel Dänzer discovered this too, and we've been discussing what to
do about it in the e-mail thread "shader_runner and glslparsertest: choose
GL version more accurately."

> --
> carl.d.worth at intel.com
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