Some formats like sub-sampled YCbCr use a block of bytes to
store the color values for more than one pixel. Update our format
table to be able to handle such formats.
In the CREATE_DUMB error code-path, we'd only free() the buffer,
however it's already inserted in the alloc->buffers list at this
point.
Instead, make sure finish_buffer() is safe to call (by populating
drm_fd) and call that function.
INVALID means that the modifier is implicit. However dumb buffers
are guaranteed to be LINEAR, so let's just advertise this. Fixes
cursors with the DRM backend: cursor planes usually only support
LINEAR.
This allows callers to specify the operations they'll perform on
the returned data pointer. The motivations for this are:
- The upcoming Linux MAP_NOSIGBUS flag may only be usable on
read-only mappings.
- gbm_bo_map with GBM_BO_TRANSFER_READ hurts performance.
