egl/wayland: Allow client->server format conversion for PRIME offload. (v2)
Support PRIME render offload between a Wayland server gpu and a Wayland client gpu with different channel ordering for their color formats, e.g., between Intel drivers which currently only support ARGB2101010 and XRGB2101010 import/display and nouveau which only supports ABGR2101010 rendering and display on nv-50 and later. In the wl_visuals table, we also store for each format an alternate sibling format which stores colors at the same precision, but with different channel ordering, e.g., ARGB2101010 <-> ABGR2101010. If a given client-gpu renderable format is not supported by the server for import, but the alternate format is supported by the server, expose the client-gpu renderable format as a valid EGLConfig to the client. At eglSwapBuffers time, during the blitImage() detiling blit from the client backbuffer to the linear buffer, the client format is converted to the server supported format. As we have to do a copy for PRIME anyway, this channel swizzling conversion comes essentially for free. Note that even if a server gpu in principle does support sampling from the clients native format, this conversion will be a performance advantage if it allows to convert to the servers preferred format for direct scanout, as the Wayland compositor may then be able to directly page-flip a fullscreen client wl_buffer onto the primary plane, or onto a hardware overlay plane, avoiding an extra data copy for desktop composition. Tested so far under Weston with: nouveau single-gpu, Intel single-gpu, AMD single-gpu, "Optimus" Intel server iGPU for display + NVidia client dGPU for rendering. v2: Implement minor review comments by Eric Engestrom: Add some comment and assert, and some style fixes for clarity. No functional change. Signed-off-by:Mario Kleiner <mario.kleiner.de@gmail.com> Reviewed-by:
Adam Jackson <ajax@redhat.com> Reviewed-by:
Daniel Stone <daniels@collabora.com> (cherry picked from commit a34b0d68)
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