[bug report] drm/amd/display: Do not elevate mem_type change to full update

[Dan Carpenter]

Hello Leo Li,

Commit 4caacd1671b7 ("drm/amd/display: Do not elevate mem_type change
to full update") from Dec 11, 2024 (linux-next), leads to the
following Smatch static checker warning:

	drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:11486 amdgpu_dm_crtc_mem_type_changed()
	error: 'new_plane_state' dereferencing possible ERR_PTR()

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c
    11475 static bool amdgpu_dm_crtc_mem_type_changed(struct drm_device *dev,
    11476                                             struct drm_atomic_state *state,
    11477                                             struct drm_crtc_state *crtc_state)
    11478 {
    11479         struct drm_plane *plane;
    11480         struct drm_plane_state *new_plane_state, *old_plane_state;
    11481 
    11482         drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
    11483                 new_plane_state = drm_atomic_get_plane_state(state, plane);
    11484                 old_plane_state = drm_atomic_get_plane_state(state, plane);
                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^
These functions can fail.

    11485 
--> 11486                 if (old_plane_state->fb && new_plane_state->fb &&
    11487                     get_mem_type(old_plane_state->fb) != get_mem_type(new_plane_state->fb))
    11488                         return true;
    11489         }
    11490 
    11491         return false;
    11492 }

regards,
dan carpenter