linux-kernel - Re: [PATCH] drm/amd/display: Fix unsigned comparison with less than zero

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Date: Mon, 1 Jul 2024 15:19:29 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc: harry.wentland@....com, sunpeng.li@....com, Rodrigo.Siqueira@....com, 
	alexander.deucher@....com, christian.koenig@....com, Xinhui.Pan@....com, 
	airlied@...il.com, daniel@...ll.ch, amd-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH] drm/amd/display: Fix unsigned comparison with less than zero

Applied.  Thanks!

On Sun, Jun 30, 2024 at 11:10 PM Jiapeng Chong
<jiapeng.chong@...ux.alibaba.com> wrote:
>
> The return value from the call to dml21_find_dc_pipes_for_plane() is int.
> However, the return value is being assigned to an unsigned int variable
> 'num_pipes', the condition if(num_pipes <= 0) is not rigorous enough,
> so making 'num_pipes' an int.
>
> ./drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c:318:6-15: WARNING: Unsigned expression compared with zero: num_pipes <= 0.
> ./drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c:360:6-15: WARNING: Unsigned expression compared with zero: num_pipes <= 0.
>
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9454
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  .../drm/amd/display/dc/dml2/dml21/dml21_wrapper.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c b/drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c
> index c310354cd5fc..9d96a31419fa 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c
> +++ b/drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c
> @@ -280,7 +280,8 @@ bool dml21_validate(const struct dc *in_dc, struct dc_state *context, struct dml
>
>  void dml21_prepare_mcache_programming(struct dc *in_dc, struct dc_state *context, struct dml2_context *dml_ctx)
>  {
> -       unsigned int num_pipes, dml_prog_idx, dml_phantom_prog_idx, dc_pipe_index;
> +       unsigned int dml_prog_idx, dml_phantom_prog_idx, dc_pipe_index;
> +       int num_pipes;
>         struct pipe_ctx *dc_main_pipes[__DML2_WRAPPER_MAX_STREAMS_PLANES__];
>         struct pipe_ctx *dc_phantom_pipes[__DML2_WRAPPER_MAX_STREAMS_PLANES__] = {0};
>
> @@ -314,10 +315,8 @@ void dml21_prepare_mcache_programming(struct dc *in_dc, struct dc_state *context
>                 }
>
>                 num_pipes = dml21_find_dc_pipes_for_plane(in_dc, context, dml_ctx, dc_main_pipes, dc_phantom_pipes, dml_prog_idx);
> -
> -               if (num_pipes <= 0 ||
> -                               dc_main_pipes[0]->stream == NULL ||
> -                               dc_main_pipes[0]->plane_state == NULL)
> +               if (num_pipes <= 0 || dc_main_pipes[0]->stream == NULL ||
> +                   dc_main_pipes[0]->plane_state == NULL)
>                         continue;
>
>                 /* get config for each pipe */
> @@ -356,10 +355,8 @@ void dml21_prepare_mcache_programming(struct dc *in_dc, struct dc_state *context
>                 pln_prog = &dml_ctx->v21.mode_programming.programming->plane_programming[dml_prog_idx];
>
>                 num_pipes = dml21_find_dc_pipes_for_plane(in_dc, context, dml_ctx, dc_main_pipes, dc_phantom_pipes, dml_prog_idx);
> -
> -               if (num_pipes <= 0 ||
> -                               dc_main_pipes[0]->stream == NULL ||
> -                               dc_main_pipes[0]->plane_state == NULL)
> +               if (num_pipes <= 0 || dc_main_pipes[0]->stream == NULL ||
> +                   dc_main_pipes[0]->plane_state == NULL)
>                         continue;
>
>                 /* get config for each pipe */
> --
> 2.20.1.7.g153144c
>