BGRA resources that use external storage (EGL image, GBM)
must keep the data store in the BGRA byte-order, while
producing the correct results when used within the host's
GL or GLES API. To maintain compatability of BGRA resources
with features such as gamma correction, texture views, and
multisampled rendering, virglrenderer swizzles BGRA texture
data to RGBA and passes GL_RGBA to the host API, then swizzles
the RGBA data back to BGRA on readout.
With external storage, virglrenderer no longer has complete
control over buffer accesses, with the possibility that buffers
will be written to and read out by other processes, such as the
display compositor. Under these circumstances, we need to emulate
the external buffer format when using it with the host rendering
API such that data is accessed from the backing buffer as RGBA
and written back as BGRA.
Signed-off-by: Ryan Neph <ryanneph@google.com>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Ryan Neph
981038e25b