On Thu, Aug 07, 2025 at 09:19:48AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> clang-21 points out a variable that is conditionally initialized
> but then dereferenced:
>
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:6: error: variable
> 'crtc_state' is used uninitialized whenever 'if' condition is false
> [-Werror,-Wsometimes-uninitialized]
> 1138 | if (plane_state->crtc)
> | ^~~~~~~~~~~~~~~~~
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1142:58: note: uninitialized use
> occurs here
> 1142 | ret = dpu_plane_atomic_check_nosspp(plane, plane_state,
> crtc_state);
> |
> ^~~~~~~~~~
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1138:2: note: remove the 'if' if
> its condition is always true
> 1138 | if (plane_state->crtc)
> | ^~~~~~~~~~~~~~~~~~~~~~
> 1139 | crtc_state = drm_atomic_get_new_crtc_state(state,
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c:1132:35: note: initialize the
> variable 'crtc_state' to silence this warning
> 1132 | struct drm_crtc_state *crtc_state;
> | ^
> | = NULL
>
> The bug is real, but the suggestion from clang to set it to NULL is
> unfortunately just as harmful as dereferencing a NULL pointer is little
> better than uninitialized data.
Having no plane->crtc is a valid setting and it is handled inside
drm_atomic_helper_check_plane_state() by setting plane_state->visible =
false and returning early. Setting crtc_state to NULL is a correct fix.
Could you please send it?
>
> Change the function to return an error in this case.
>
> Fixes: 774bcfb73176 ("drm/msm/dpu: add support for virtual planes")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
--
With best wishes
Dmitry
