[bug report] drm/vmwgfx: Add and connect plane helper functions

[Dan Carpenter]

Hello Sinclair Yeh,

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

The patch 060e2ad57041: "drm/vmwgfx: Add and connect plane helper 
functions" from Mar 23, 2017, leads to the following Smatch complaint:

    drivers/gpu/drm/vmwgfx/vmwgfx_kms.c:466 vmw_du_primary_plane_atomic_check()
    error: we previously assumed 'crtc' could be null (see line 463)

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
   441  int vmw_du_primary_plane_atomic_check(struct drm_plane *plane,
   442                                        struct drm_plane_state *state)
   443  {
   444          struct drm_crtc_state *crtc_state = NULL;
   445          struct drm_framebuffer *new_fb = state->fb;
   446          struct drm_rect clip = {};
   447          int ret;
   448  
   449          if (state->crtc)
                    ^^^^^^^^^^^
Check for NULL

   450                  crtc_state = drm_atomic_get_new_crtc_state(state->state, state->crtc);
   451  
   452          if (crtc_state && crtc_state->enable) {
   453                  clip.x2 = crtc_state->adjusted_mode.hdisplay;
   454                  clip.y2 = crtc_state->adjusted_mode.vdisplay;
   455          }
   456  
   457          ret = drm_atomic_helper_check_plane_state(state, crtc_state, &clip,
   458                                                    DRM_PLANE_HELPER_NO_SCALING,
   459                                                    DRM_PLANE_HELPER_NO_SCALING,
   460                                                    false, true);
   461  
   462		if (!ret && new_fb) {
   463			struct drm_crtc *crtc = state->crtc;
   464			struct vmw_connector_state *vcs;
   465			struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
   466			struct vmw_private *dev_priv = vmw_priv(crtc->dev);
                                                                ^^^^^^^^^
Unchecked dereference

   467			struct vmw_framebuffer *vfb = vmw_framebuffer_to_vfb(new_fb);
   468	

regards,
dan carpenter