requested to merge Spintzyk/xserver:branch1.20/disable_reverse_prime_for_evdi into server-1.20-branch
This is port of fix for #1183 (closed) to xserver-1.20-branch
This mode for displays running on evdi/udl as side effect of failed glamor_egl_init reverse_prime_offload_mode was initialized to FALSE
After Mesa upgrade to 21.0.0 GL_RENDERER is not llvmpipe that results in successful glamor_egl_init and reverse_prime_offload_mode enabled.
This commit is explicitly disabling reverse_prime_offload_mode for evdi and udl drivers