drm/atomic: add commit_planes_on_crtc helper

[Dan Carpenter]

Hello Maarten Lankhorst,

This is a semi-automatic email about new static checker warnings.

The patch 32975e952e85: "drm/atomic: add commit_planes_on_crtc 
helper" from May 19, 2015, leads to the following Smatch complaint:

drivers/gpu/drm/drm_atomic_helper.c:1244 
drm_atomic_helper_commit_planes_on_crtc()
         error: we previously assumed 'crtc_funcs' could be null (see line 1221)

drivers/gpu/drm/drm_atomic_helper.c
  1220          crtc_funcs = crtc->helper_private;
  1221          if (crtc_funcs && crtc_funcs->atomic_begin)
                    ^^^^^^^^^^
Check.

  1222                  crtc_funcs->atomic_begin(crtc);
  1223  
  1224          drm_for_each_plane_mask(plane, crtc->dev, plane_mask) {
  1225                  struct drm_plane_state *old_plane_state =
  1226                          drm_atomic_get_existing_plane_state(old_state, 
plane);
  1227                  const struct drm_plane_helper_funcs *plane_funcs;
  1228  
  1229                  plane_funcs = plane->helper_private;
  1230  
  1231                  if (!old_plane_state || !plane_funcs)
  1232                          continue;
  1233  
  1234                  WARN_ON(plane->state->crtc && plane->state->crtc != 
crtc);
  1235  
  1236                  if (drm_atomic_plane_disabling(plane, old_plane_state) 
&&
  1237                      plane_funcs->atomic_disable)
  1238                          plane_funcs->atomic_disable(plane, 
old_plane_state);
  1239                  else if (plane->state->crtc ||
  1240                           drm_atomic_plane_disabling(plane, 
old_plane_state))
  1241                          plane_funcs->atomic_update(plane, 
old_plane_state);
  1242          }
  1243  
  1244          if (crtc_funcs->atomic_flush)
                    ^^^^^^^^^^
Unchecked dereference.

  1245                  crtc_funcs->atomic_flush(crtc);
  1246  }

regards,
dan carpenter