drm/docs: More links for implicit/explicit fencing.

 * There is no need for &drm_plane_helper_funcs.cleanup_fb hook for simple

 * gem based framebuffer drivers which have their buffers always pinned in

 * memory.

 *

 * See drm_atomic_set_fence_for_plane() for a discussion of implicit and

 * explicit fencing in atomic modeset updates.

 */

int drm_gem_fb_prepare_fb(struct drm_plane *plane,

			  struct drm_plane_state *state)

 * &dma_buf attached, extracts the exclusive fence and attaches it to plane

 * state for the atomic helper to wait on. Drivers can use this as their

 * &drm_simple_display_pipe_funcs.prepare_fb callback.

 *

 * See drm_atomic_set_fence_for_plane() for a discussion of implicit and

 * explicit fencing in atomic modeset updates.

 */

int drm_gem_fb_simple_display_pipe_prepare_fb(struct drm_simple_display_pipe *pipe,

					      struct drm_plane_state *plane_state)

	 *

	 * Optional fence to wait for before scanning out @fb. The core atomic

	 * code will set this when userspace is using explicit fencing. Do not

	 * write this directly for a driver's implicit fence, use

	 * write this field directly for a driver's implicit fence, use

	 * drm_atomic_set_fence_for_plane() to ensure that an explicit fence is

	 * preserved.

	 *