Re: [PATCH] drm/amd/display: Fix -Wuninitialized in dm_helpers_dp_mst_send_payload_allocation()

Hamza Mahfooz <hamza.mahfooz@xxxxxxx> · Wed, 13 Sep 2023 15:57:21 -0400

On 9/13/23 15:54, Alex Deucher wrote:
On Wed, Sep 13, 2023 at 12:17 PM Hamza Mahfooz <hamza.mahfooz@xxxxxxx> wrote:


On 9/13/23 12:10, Nathan Chancellor wrote:
When building with clang, there is a warning (or error when
CONFIG_WERROR is set):

    drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_helpers.c:368:21: error: variable 'old_payload' is uninitialized when used here [-Werror,-Wuninitialized]
      368 |                                                  new_payload, old_payload);
          |                                                               ^~~~~~~~~~~
    drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_helpers.c:344:61: note: initialize the variable 'old_payload' to silence this warning
      344 |         struct drm_dp_mst_atomic_payload *new_payload, *old_payload;
          |                                                                    ^
          |                                                                     = NULL
    1 error generated.

This variable is not required outside of this function so allocate
old_payload on the stack and pass it by reference to
dm_helpers_construct_old_payload(), resolving the warning.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1931
Fixes: 5aa1dfcdf0a4 ("drm/mst: Refactor the flow for payload allocation/removement")
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>

Reviewed-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>

Hm, seems like this was pushed through drm-misc-next and as such our CI
didn't get a chance to test it.

Can you push this to drm-misc?  That is where Wayne's patches landed.
If not, I can push it.

No need, I cherry-picked Wayne's patches to amd-staging-drm-next and
applied Nathan's fix.


Alex




---
   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 6 +++---
   1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 9ad509279b0a..c4c35f6844f4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -341,7 +341,7 @@ bool dm_helpers_dp_mst_send_payload_allocation(
       struct amdgpu_dm_connector *aconnector;
       struct drm_dp_mst_topology_state *mst_state;
       struct drm_dp_mst_topology_mgr *mst_mgr;
-     struct drm_dp_mst_atomic_payload *new_payload, *old_payload;
+     struct drm_dp_mst_atomic_payload *new_payload, old_payload;
       enum mst_progress_status set_flag = MST_ALLOCATE_NEW_PAYLOAD;
       enum mst_progress_status clr_flag = MST_CLEAR_ALLOCATED_PAYLOAD;
       int ret = 0;
@@ -365,8 +365,8 @@ bool dm_helpers_dp_mst_send_payload_allocation(
               ret = drm_dp_add_payload_part2(mst_mgr, mst_state->base.state, new_payload);
       } else {
               dm_helpers_construct_old_payload(stream->link, mst_state->pbn_div,
-                                              new_payload, old_payload);
-             drm_dp_remove_payload_part2(mst_mgr, mst_state, old_payload, new_payload);
+                                              new_payload, &old_payload);
+             drm_dp_remove_payload_part2(mst_mgr, mst_state, &old_payload, new_payload);
       }

       if (ret) {

---
base-commit: 8569c31545385195bdb0c021124e68336e91c693
change-id: 20230913-fix-wuninitialized-dm_helpers_dp_mst_send_payload_allocation-c37b33aaad18

Best regards,
--
Hamza

--
Hamza







