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

[Hamza Mahfooz]

On 9/13/23 15:54, Alex Deucher wrote:
> On Wed, Sep 13, 2023 at 12:17 PM Hamza Mahfooz <hamza.mahfooz at amd.com> 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 at kernel.org>
>>
>> Reviewed-by: Hamza Mahfooz <hamza.mahfooz at amd.com>
>>
>> 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