linux-kernel - Re: [PATCH] drm/msm/dpu: Delete a variable initialisation before a null pointer check in two functions

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Message-ID: <90f32378-fa1c-a23e-2db2-2e83a42fd45e@linaro.org>
Date:   Tue, 11 Apr 2023 19:43:06 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Markus Elfring <Markus.Elfring@....de>,
        kernel-janitors@...r.kernel.org, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Archit Taneja <architt@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Vinod Koul <vkoul@...nel.org>
Cc:     cocci@...ia.fr, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/dpu: Delete a variable initialisation before a
 null pointer check in two functions

On 11/04/2023 19:38, Markus Elfring wrote:
> Date: Tue, 11 Apr 2023 18:24:24 +0200
> 
> The address of a data structure member was determined before
> a corresponding null pointer check in the implementation of
> the functions “dpu_hw_pp_enable_te” and “dpu_hw_pp_get_vsync_info”.
> 
> Thus avoid the risk for undefined behaviour by removing extra
> initialisations for the variable “c” (also because it was already
> reassigned with the same value behind this pointer check).
> 
> This issue was detected by using the Coccinelle software.
> 
> Fixes: 25fdd5933e4c0f5fe2ea5cd59994f8ac5fbe90ef ("drm/msm: Add SDM845 DPU support")

Plese follow the format for the Fixes tags and limit the hash to 12 
chars. Proper tag:

Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")

Other than that LGTM.

> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> index 0fcad9760b6f..870ab3ebbc94 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> @@ -176,7 +176,7 @@ static int dpu_hw_pp_enable_te(struct dpu_hw_pingpong *pp, bool enable)
>   static int dpu_hw_pp_connect_external_te(struct dpu_hw_pingpong *pp,
>   		bool enable_external_te)
>   {
> -	struct dpu_hw_blk_reg_map *c = &pp->hw;
> +	struct dpu_hw_blk_reg_map *c;
>   	u32 cfg;
>   	int orig;
> 
> @@ -221,7 +221,7 @@ static int dpu_hw_pp_get_vsync_info(struct dpu_hw_pingpong *pp,
> 
>   static u32 dpu_hw_pp_get_line_count(struct dpu_hw_pingpong *pp)
>   {
> -	struct dpu_hw_blk_reg_map *c = &pp->hw;
> +	struct dpu_hw_blk_reg_map *c;
>   	u32 height, init;
>   	u32 line = 0xFFFF;
> 
> --
> 2.40.0
> 

-- 
With best wishes
Dmitry