linux-kernel - Re: [Freedreno] [PATCH] drm/msm/dp: Drop unnecessary NULL checks after container

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Date:   Tue, 25 May 2021 11:34:16 -0700
From:   abhinavk@...eaurora.org
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel@...ll.ch>,
        freedreno@...ts.freedesktop.org
Subject: Re: [Freedreno] [PATCH] drm/msm/dp: Drop unnecessary NULL checks
 after container_of

On 2021-05-24 20:20, 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 check on the result of container_of() is therefore unnecessary
> and misleading. Remove it.
> 
> 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
> ...+>
> 
> While at it, remove unused but assigned variable hpd in
> dp_display_usbpd_attention_cb().
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Abhinav Kumar <abhinavk@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 25 -------------------------
>  1 file changed, 25 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c
> b/drivers/gpu/drm/msm/dp/dp_display.c
> index 1784e119269b..a74e7ef96fcf 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -208,10 +208,6 @@ static int dp_display_bind(struct device *dev,
> struct device *master,
> 
>  	dp = container_of(g_dp_display,
>  			struct dp_display_private, dp_display);
> -	if (!dp) {
> -		DRM_ERROR("DP driver bind failed. Invalid driver data\n");
> -		return -EINVAL;
> -	}
> 
>  	dp->dp_display.drm_dev = drm;
>  	priv = drm->dev_private;
> @@ -252,10 +248,6 @@ static void dp_display_unbind(struct device *dev,
> struct device *master,
> 
>  	dp = container_of(g_dp_display,
>  			struct dp_display_private, dp_display);
> -	if (!dp) {
> -		DRM_ERROR("Invalid DP driver data\n");
> -		return;
> -	}
> 
>  	dp_power_client_deinit(dp->power);
>  	dp_aux_unregister(dp->aux);
> @@ -406,11 +398,6 @@ static int dp_display_usbpd_configure_cb(struct
> device *dev)
> 
>  	dp = container_of(g_dp_display,
>  			struct dp_display_private, dp_display);
> -	if (!dp) {
> -		DRM_ERROR("no driver data found\n");
> -		rc = -ENODEV;
> -		goto end;
> -	}
> 
>  	dp_display_host_init(dp, false);
> 
> @@ -437,11 +424,6 @@ static int dp_display_usbpd_disconnect_cb(struct
> device *dev)
> 
>  	dp = container_of(g_dp_display,
>  			struct dp_display_private, dp_display);
> -	if (!dp) {
> -		DRM_ERROR("no driver data found\n");
> -		rc = -ENODEV;
> -		return rc;
> -	}
> 
>  	dp_add_event(dp, EV_USER_NOTIFICATION, false, 0);
> 
> @@ -502,7 +484,6 @@ static int dp_display_usbpd_attention_cb(struct 
> device *dev)
>  	int rc = 0;
>  	u32 sink_request;
>  	struct dp_display_private *dp;
> -	struct dp_usbpd *hpd;
> 
>  	if (!dev) {
>  		DRM_ERROR("invalid dev\n");
> @@ -511,12 +492,6 @@ static int dp_display_usbpd_attention_cb(struct
> device *dev)
> 
>  	dp = container_of(g_dp_display,
>  			struct dp_display_private, dp_display);
> -	if (!dp) {
> -		DRM_ERROR("no driver data found\n");
> -		return -ENODEV;
> -	}
> -
> -	hpd = dp->usbpd;
> 
>  	/* check for any test request issued by sink */
>  	rc = dp_link_process_request(dp->link);