drm/fbdev-helper: Update documentation on obsolete callbacks

The old callbacks lastclose and output_poll_changed are deprecated and
unused. Remove them from the documentation.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812083000.337744-7-tzimmermann@suse.de

drivers/gpu/drm/drm_fb_helper.c

@@ -89,14 +89,6 @@ static DEFINE_MUTEX(kernel_fb_helper_lock);
  * interfaces. Drivers that use one of the shared memory managers, TTM, SHMEM,
  * DMA, should instead use the corresponding fbdev emulation.
  *
- * Existing fbdev implementations should restore the fbdev console by using
- * drm_fb_helper_lastclose() as their &drm_driver.lastclose callback.
- * They should also notify the fb helper code from updates to the output
- * configuration by using drm_fb_helper_output_poll_changed() as their
- * &drm_mode_config_funcs.output_poll_changed callback. New implementations
- * of fbdev should be build on top of struct &drm_client_funcs, which handles
- * this automatically. Setting the old callbacks should be avoided.
- *
  * For suspend/resume consider using drm_mode_config_helper_suspend() and
  * drm_mode_config_helper_resume() which takes care of fbdev as well.
  *
@@ -260,12 +252,12 @@ __drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper,
  * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration
  * @fb_helper: driver-allocated fbdev helper, can be NULL
  *
- * This should be called from driver's drm &drm_driver.lastclose callback
- * when implementing an fbcon on top of kms using this helper. This ensures that
- * the user isn't greeted with a black screen when e.g. X dies.
+ * This helper should be called from fbdev emulation's &drm_client_funcs.restore
+ * callback. It ensures that the user isn't greeted with a black screen when the
+ * userspace compositor releases the display device.
  *
- * RETURNS:
- * Zero if everything went ok, negative error code otherwise.
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
  */
 int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
 {
@@ -2003,8 +1995,8 @@ EXPORT_SYMBOL(drm_fb_helper_hotplug_event);
  * drm_fb_helper_lastclose - DRM driver lastclose helper for fbdev emulation
  * @dev: DRM device
  *
- * This function can be used as the &drm_driver->lastclose callback for drivers
- * that only need to call drm_fb_helper_restore_fbdev_mode_unlocked().
+ * This function is obsolete. Call drm_fb_helper_restore_fbdev_mode_unlocked()
+ * instead.
  */
 void drm_fb_helper_lastclose(struct drm_device *dev)
 {