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libgbm: Problems importing dmabuf on device with multiple DRM devices

System information

  • Platform: i.MX6 SoC
  • OS: Debian Bullseye
  • GPU: Vivante GC2000
  • Kernel version: 5.10.43
  • Mesa version: OpenGL ES 2.0 Mesa 20.3.5 (From weston logs)
  • Desktop manager and compositor: Weston

The issue

The kernel exposes two drm devices on i.MX6 -

  • card0 / render128 - etnaviv
  • card1 - imx-drm

From digging into the mesa side of things - it looks like the kmsro driver is being used on the device.

When importing a dmabuf (coming from gstreamer) the following steps are executed in weston -

  1. the buffer object is imported using gbm_bo_import
  2. get handles for planes - https://gitlab.freedesktop.org/wayland/weston/-/blob/9.0/libweston/backend-drm/fb.c#L355
  3. create a framebuffer using drmAddFb()

It seems that the handles returned in step 2 are based on the render device rather than the display / scanout device. The call to addFb() in Step 3 results in the following debug message from the kernel DRM sub-system -

Failed to lookup GEM object

As a test, the problem goes away when the etnaviv kernel driver is disabled.

Let me know if there are any other details I can provide to help fix the issue.

The issue seems to have similar symptoms as reported in this thread at - https://lists.freedesktop.org/archives/etnaviv/2018-July/001864.html. But I am not familiar with android / mesa so could be mistaken.

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