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

[Alex Deucher]

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.

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
>