[v1] drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

[PATCH RESEND] drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Posted by sunliming@linux.dev 1 week, 2 days ago

From: sunliming <sunliming@kylinos.cn>

Fix below smatch warnings:
drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
warn: variable dereferenced before check 'ctx' (see line 159)

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
Signed-off-by: sunliming <sunliming@kylinos.cn>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
index e65f1fc026fd..312ee6597ab1 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
@@ -156,11 +156,13 @@ static void dpu_hw_sspp_setup_pe_config_v13(struct dpu_hw_sspp *ctx,
 	u8 color;
 	u32 lr_pe[4], tb_pe[4];
 	const u32 bytemask = 0xff;
-	u32 offset = ctx->cap->sblk->sspp_rec0_blk.base;
+	u32 offset;
 
 	if (!ctx || !pe_ext)
 		return;
 
+	offset = ctx->cap->sblk->sspp_rec0_blk.base;
+
 	c = &ctx->hw;
 	/* program SW pixel extension override for all pipes*/
 	for (color = 0; color < DPU_MAX_PLANES; color++) {
-- 
2.25.1

Re: [PATCH RESEND] drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Posted by Rob Clark 5 days, 21 hours ago

On Wed, Jan 28, 2026 at 6:50 PM <sunliming@linux.dev> wrote:
>
> From: sunliming <sunliming@kylinos.cn>
>
> Fix below smatch warnings:
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
> warn: variable dereferenced before check 'ctx' (see line 159)
>
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <error27@gmail.com>
> Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
> Signed-off-by: sunliming <sunliming@kylinos.cn>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
> index e65f1fc026fd..312ee6597ab1 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c
> @@ -156,11 +156,13 @@ static void dpu_hw_sspp_setup_pe_config_v13(struct dpu_hw_sspp *ctx,
>         u8 color;
>         u32 lr_pe[4], tb_pe[4];
>         const u32 bytemask = 0xff;
> -       u32 offset = ctx->cap->sblk->sspp_rec0_blk.base;
> +       u32 offset;
>
>         if (!ctx || !pe_ext)
>                 return;
>
> +       offset = ctx->cap->sblk->sspp_rec0_blk.base;
> +

btw, in this case (and probably most/all such cases in dpu code that
I've looked at) we should probably just remove the impossible null
checks.  (Although the extra indirections in the dpu code make it
harder to see that they are impossible..)

BR,
-R

>         c = &ctx->hw;
>         /* program SW pixel extension override for all pipes*/
>         for (color = 0; color < DPU_MAX_PLANES; color++) {
> --
> 2.25.1
>

Re: [PATCH RESEND] drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Posted by Dmitry Baryshkov 1 week ago

On Thu, Jan 29, 2026 at 10:49:19AM +0800, sunliming@linux.dev wrote:
> From: sunliming <sunliming@kylinos.cn>
> 
> Fix below smatch warnings:
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
> warn: variable dereferenced before check 'ctx' (see line 159)
> 
> Reported-by: kernel test robot <lkp@intel.com>

Closes? (you can just reply to this email with the Closes: line and the
URL for the LKP report).

> Reported-by: Dan Carpenter <error27@gmail.com>
> Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
> Signed-off-by: sunliming <sunliming@kylinos.cn>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>


-- 
With best wishes
Dmitry

Re: [PATCH RESEND] drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Posted by Dan Carpenter 1 week, 2 days ago

On Thu, Jan 29, 2026 at 10:49:19AM +0800, sunliming@linux.dev wrote:
> From: sunliming <sunliming@kylinos.cn>
> 
> Fix below smatch warnings:
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
> warn: variable dereferenced before check 'ctx' (see line 159)
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <error27@gmail.com>
> Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
> Signed-off-by: sunliming <sunliming@kylinos.cn>
> ---

Could you capitalize your name?  It's supposed to be a bit formal like
signing a legal document.

This isn't a RESEND, it's a v2.  A RESEND means we accidentally ignored
your email so now you have to send the exact same email again.

https://staticthinking.wordpress.com/2022/07/27/how-to-send-a-v2-patch/

regards,
dan carpenter