[Mesa-dev] [PATCH 4/4] configure.ac: check for Glamor requirements only when needed

[Marek Olšák]

On Wed, Oct 19, 2016 at 2:40 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 18 October 2016 at 23:00, Marek Olšák <maraeo at gmail.com> wrote:
>> From: Marek Olšák <marek.olsak at amd.com>
>>
>> ---
>>  configure.ac | 37 +++++++++++++++++++++++++++----------
>>  1 file changed, 27 insertions(+), 10 deletions(-)
>>
>> diff --git a/configure.ac b/configure.ac
>> index 12c8165..17dfafd 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -2296,35 +2296,52 @@ dnl Gallium helper functions
>>  dnl
>>  gallium_require_llvm() {
>>      if test "x$MESA_LLVM" = x0; then
>>          case "$host" in *gnux32) return;; esac
>>          case "$host_cpu" in
>>          i*86|x86_64|amd64) AC_MSG_ERROR([LLVM is required to build $1 on x86 and x86_64]);;
>>          esac
>>      fi
>>  }
>>
>> -dnl This is for Glamor. Skip this if OpenGL is disabled.
>> -require_egl_drm() {
>> +dnl If EGL/X11 or GLX is enabled, make sure they are usable.
>> +check_glamor_requirements() {
>
> With the previous patches you no longer need this, due to the following:
>  - The correct option is the default one
>  - If one is missing libgbm.so, libglamoregl.so will fail to load
> [with decent commit message]
>  - With recent fix from Chad, we won't advertise the
> EGL_MESA_platform_gbm extension when EGL is build w/o it.
>  - The interface between DRI loaders and drivers is stable. So one
> shouldn't need to rebuild EGL/gbm if they're only interested in the
> latest fixes in the radeonsi driver.
>
> Either way, if you really want this please use something like the following:
>
> if test x$enable_egl = xyes; then
>   case "$with_egl_platforms" in
>     *drm*)
>       ;;
>     *)
>       AC_MSG_ERROR([--with-egl-platforms=drm is required to build the
> $1 driver.])
>       ;;
>   esac
> fi
>
> One doesn't need any of the enable_opengl, enable_gbm or alike tests.
> Furthermore glamor relies on the gbm/drm EGL platform so the x11 check
> is superfluous.

I think there is some misunderstanding.

OpenGL X11/DRI acceleration is enabled by the build system:
- for GLX by setting $enable_glx = dri
- for EGL by setting $with_egl_platforms = *x11*

The following code checks if OpenGL on X11/DRI is enabled:

    if test "x$enable_opengl" = xno; then
        return 0
    fi

    need_glamor=no

    if test "x$enable_glx" = xdri; then # GLX
        need_glamor=yes
    fi

    case "$with_egl_platforms" in # EGL
        *x11*)
            need_glamor=yes
            ;;
    esac


Once we know that OpenGL on X11/DRI is being built (need_glamor=yes,
though that's a misnomer), we have to make sure it's usable. This is
where GBM and EGL/DRM are required. You can't have working OpenGL on
X11/DRI without those two requirements. Therefore, checks like this
follow:

        if test "x$enable_gbm" != xyes; then ....

        case "$with_egl_platforms" in
            *drm*) ...

If you don't want X11/DRI support, just disable it. But this patch
won't let you build radeonsi for X11/DRI without GBM and EGL/DRM.
There was also the argument that the system-provided libgbm can be
used, but I have doubts about the stability of its interface.

Marek