I've brought this up in the past, but I have some patches implementing
it now, so I was hoping to get some further feedback on the idea of
supporting GBM backends external to Mesa.
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9902
From my reading, the GBM core code was intended to support, or perhaps
at some point in the past did support loading backends other than the
built-in DRI one. This series extends the current code to enable loading
of alternate backends in general, and as a straw-man proposal,
specifically uses the DRM driver name of the FD passed to
gbm_create_device() to construct a library name of a potential alternate
backend. Other schemes could be implemented on top of the basic
functionality added here, but this simple one seemed sufficient.
Issues addressed in the series:
-The ability to dynamically load backends from DSOs.
-Thread-safe tracking and refcounting of dynamically-loaded backends.
-Versioning of the GBM driver ABI to enable backwards and forwards
binary compatibility between the GBM loader and backends.
-Discovery of alternate/external backend DSOs.
Here's a rundown of the backend discovery logic implemented in the series:
-If the GBM_BACKEND env var is set, attempt to load the backend library
it names and create a device from it if found.
-If that fails or the env var is not set, call drmGetVersion() on the
fd, and if that succeeds, attempt to load libgbm_<DRM driver name>.so.0
and create a device from it if found.
-If that fails, try the built-in DRI backend.
Thanks,
-James
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