[Mesa-dev] [PATCH 1/2] gbm: Enable DRI2 fence extension in the GBM DRI backend

Philipp Zabel p.zabel at pengutronix.de
Wed May 25 14:46:15 UTC 2016

Am Mittwoch, den 25.05.2016, 16:01 +0200 schrieb Marek Olšák:
> On Wed, May 25, 2016 at 3:44 PM, Philipp Zabel <p.zabel at pengutronix.de> wrote:
> > Am Dienstag, den 10.05.2016, 17:35 +0200 schrieb Philipp Zabel:
> >> To support the EGL_KHR_fence_sync extension on the DRM EGL platform,
> >> add the DRI2 fence extension to the dri_core_extensions match table.
> >>
> >> Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
> >
> > Gentle ping. Is this about the right way to enable the
> > EGL_KHR_fence_sync extension on DRM EGL platforms?
> Unlikely. Where are the __DRI2fenceExtension callbacks implemented?

The callbacks are implemented and added to the dri_screen_extensions[]
array in src/gallium/state_trackers/dri/dri2.c. The array is assigned to
the __DRIscreen member "extensions" in dri2_init_screen().

dri_screen_create_dri2() in src/gbm/backends/dri/gbm_dri.c
then obtains the extensions array via dri->core->getExtensions() and
binds selected extensions to the gbm_dri_device according to the
placement information in the dri_core_extensions[] array.
This was already done for the flush and image extensions, so I have
similarly added a fence extension pointer to the gbm_dri_device and an
entry to dri_core_extensions to have it initialized from the dri2
extension array that already contained the fence extension.

dri2_initialize_drm() in src/egl/drivers/dri2/platform_drm.c
then copies the extension pointers from the gbm_dri_device
dri2_dpy->gbm_dri into the dri2_egl_display dri2_dpy proper.
This also was already done for a few other extensions, among them image
and flush, and the dri2_egl_display already has a fence pointer that I
used to assign to the gbm_dri_device's new fence pointer.

dri2_setup_screen() in src/egl/drivers/dri2/egl_dri2.c later checks
dri2_dpy->fence to enable the extension.


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