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

[Alex Deucher]

On Wed, Sep 13, 2023 at 4:46 PM Hamza Mahfooz <hamza.mahfooz at amd.com> wrote:
>
> On 9/13/23 16:03, Alex Deucher wrote:
> > On Wed, Sep 13, 2023 at 3:57 PM Hamza Mahfooz <hamza.mahfooz at amd.com> wrote:
> >>
> >>
> >> 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.
> >
> > Yes, but we can only have patches go upstream via one tree.  Wayne's
> > patches are in drm-misc, so that is where the fix should be.  It's
> > fine to have them in amd-staging-drm-next for testing purposes, but I
> > won't be upstreaming them via the amdgpu -next tree since they are
> > already in drm-misc.
>
> In that case can you push it to drm-misc?

Pushed.  Thanks!

Alex


Alex

>
> >
> > Alex
> >
> >>
> >>>
> >>> 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
> >>
> --
> Hamza
>