virtio-gpu api: Add a comment on VIRTIO_GPU_SHM_ID_HOST_VISIBLE

This provides a description of how the kernel driver uses the
shmid to determine capabilities.

Signed-off-by: Anthoine Bourgeois <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Gerd Hoffmann <[e-mail]>

include/uapi/linux/virtio_gpu.h

···
 
 enum virtio_gpu_shm_id {
 	VIRTIO_GPU_SHM_ID_UNDEFINED = 0,
+	/*
+	 * VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB
+	 * VIRTIO_GPU_CMD_RESOURCE_UNMAP_BLOB
+	 */
 	VIRTIO_GPU_SHM_ID_HOST_VISIBLE = 1
 };