linux-kernel - Re: [PATCH] drm/msm/disp/dpu1/dpu_encoder: Drop unnecessary NULL checks after container

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Date:   Tue, 25 May 2021 11:18:08 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/disp/dpu1/dpu_encoder: Drop unnecessary NULL
 checks after container_of

On Tue 25 May 06:29 CDT 2021, Guenter Roeck wrote:

> The result of container_of() operations is never NULL unless the embedded
> element is the first element of the structure. This is not the case here.
> The NULL checks on the result of container_of() are therefore unnecessary
> and misleading. Remove them.
> 
> This change was made automatically with the following Coccinelle script.
> 
> @@
> type t;
> identifier v;
> statement s;
> @@
> 
> <+...
> (
>   t v = container_of(...);
> |
>   v = container_of(...);
> )
>   ...
>   when != v
> - if (\( !v \| v == NULL \) ) s
> ...+>
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 8d942052db8a..a573fe211375 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -1453,11 +1453,6 @@ static void dpu_encoder_off_work(struct work_struct *work)
>  	struct dpu_encoder_virt *dpu_enc = container_of(work,
>  			struct dpu_encoder_virt, delayed_off_work.work);
>  
> -	if (!dpu_enc) {
> -		DPU_ERROR("invalid dpu encoder\n");
> -		return;
> -	}
> -
>  	dpu_encoder_resource_control(&dpu_enc->base,
>  						DPU_ENC_RC_EVENT_ENTER_IDLE);
>  
> @@ -1797,11 +1792,6 @@ static void dpu_encoder_vsync_event_work_handler(struct kthread_work *work)
>  			struct dpu_encoder_virt, vsync_event_work);
>  	ktime_t wakeup_time;
>  
> -	if (!dpu_enc) {
> -		DPU_ERROR("invalid dpu encoder\n");
> -		return;
> -	}
> -
>  	if (dpu_encoder_vsync_time(&dpu_enc->base, &wakeup_time))
>  		return;
>  
> -- 
> 2.25.1
>