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

[Hamza Mahfooz]

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.


> ---
>   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