[PATCH] drm/amd: Initialize remove_mpcc in dcn201_update_mpcc()

[PATCH] drm/amd: Initialize remove_mpcc in dcn201_update_mpcc()

[Nathan Chancellor]

Clang warns:

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:505:6: error: variable 'remove_mpcc' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        if (mpc->funcs->get_mpcc_for_dpp_from_secondary)
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:509:6: note: uninitialized use occurs here
        if (remove_mpcc != NULL && mpc->funcs->remove_mpcc_from_secondary)
            ^~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:505:2: note: remove the 'if' if its condition is always true
        if (mpc->funcs->get_mpcc_for_dpp_from_secondary)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:442:26: note: initialize the variable 'remove_mpcc' to silence this warning
        struct mpcc *remove_mpcc;
                                ^
                                 = NULL
1 error generated.

The code already handles remove_mpcc being NULL just fine so initialize
it to NULL at the beginning of the function so it is never used
uninitialized.

Fixes: ff7e396f822f ("drm/amd/display: add cyan_skillfish display support")
Link: https://github.com/ClangBuiltLinux/linux/issues/1469
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
index ceaaeeb8f2de..cfd09b3f705e 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
@@ -439,7 +439,7 @@ void dcn201_update_mpcc(struct dc *dc, struct pipe_ctx *pipe_ctx)
 	bool per_pixel_alpha = pipe_ctx->plane_state->per_pixel_alpha && pipe_ctx->bottom_pipe;
 	int mpcc_id, dpp_id;
 	struct mpcc *new_mpcc;
-	struct mpcc *remove_mpcc;
+	struct mpcc *remove_mpcc = NULL;
 	struct mpc *mpc = dc->res_pool->mpc;
 	struct mpc_tree *mpc_tree_params = &(pipe_ctx->stream_res.opp->mpc_tree_params);
 

base-commit: 30fc33064c846df29888c3c61e30a064aad3a342
-- 
2.33.0.591.gddb1055343

Re: [PATCH] drm/amd: Initialize remove_mpcc in dcn201_update_mpcc()

[Alex Deucher]

Applied.  Thanks!

Alex

On Thu, Sep 30, 2021 at 12:16 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Clang warns:
>
> drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:505:6: error: variable 'remove_mpcc' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>         if (mpc->funcs->get_mpcc_for_dpp_from_secondary)
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:509:6: note: uninitialized use occurs here
>         if (remove_mpcc != NULL && mpc->funcs->remove_mpcc_from_secondary)
>             ^~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:505:2: note: remove the 'if' if its condition is always true
>         if (mpc->funcs->get_mpcc_for_dpp_from_secondary)
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_hwseq.c:442:26: note: initialize the variable 'remove_mpcc' to silence this warning
>         struct mpcc *remove_mpcc;
>                                 ^
>                                  = NULL
> 1 error generated.
>
> The code already handles remove_mpcc being NULL just fine so initialize
> it to NULL at the beginning of the function so it is never used
> uninitialized.
>
> Fixes: ff7e396f822f ("drm/amd/display: add cyan_skillfish display support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1469
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> index ceaaeeb8f2de..cfd09b3f705e 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> @@ -439,7 +439,7 @@ void dcn201_update_mpcc(struct dc *dc, struct pipe_ctx *pipe_ctx)
>         bool per_pixel_alpha = pipe_ctx->plane_state->per_pixel_alpha && pipe_ctx->bottom_pipe;
>         int mpcc_id, dpp_id;
>         struct mpcc *new_mpcc;
> -       struct mpcc *remove_mpcc;
> +       struct mpcc *remove_mpcc = NULL;
>         struct mpc *mpc = dc->res_pool->mpc;
>         struct mpc_tree *mpc_tree_params = &(pipe_ctx->stream_res.opp->mpc_tree_params);
>
>
> base-commit: 30fc33064c846df29888c3c61e30a064aad3a342
> --
> 2.33.0.591.gddb1055343
>