linux-kernel - Re: [PATCH -next] drm/shmob: Fix return value check in shmob_drm

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Message-ID: <279140cd-2719-9828-7399-99848411ed51@ideasonboard.com>
Date:   Mon, 17 Dec 2018 11:28:48 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     YueHaibing <yuehaibing@...wei.com>,
        laurent.pinchart@...asonboard.com, airlied@...ux.ie,
        daniel@...ll.ch
Cc:     linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH -next] drm/shmob: Fix return value check in
 shmob_drm_probe

Hi YeuHaibing,

On 17/12/2018 09:18, YueHaibing wrote:
> In case of error, the function devm_ioremap_resource() returns ERR_PTR()
> and never returns NULL. The NULL test in the return value check should
> be replaced with IS_ERR().
> 

This looks correct to me.

I wonder if this failure pattern occurs a lot in the kernel.

I wonder if we have a cocci-check for this ?
It seems the closest we have is scripts/coccinelle/null/eno.cocci.

Perhaps that could be extended sometime to check these globally.

> Fixes: 8f1597c8f1a5 ("drm: shmobile: Perform initialization/cleanup at probe/remove time")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

> ---
>  drivers/gpu/drm/shmobile/shmob_drm_drv.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/shmobile/shmob_drm_drv.c b/drivers/gpu/drm/shmobile/shmob_drm_drv.c
> index 8554102..f2cfd16 100644
> --- a/drivers/gpu/drm/shmobile/shmob_drm_drv.c
> +++ b/drivers/gpu/drm/shmobile/shmob_drm_drv.c
> @@ -229,8 +229,8 @@ static int shmob_drm_probe(struct platform_device *pdev)
>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	sdev->mmio = devm_ioremap_resource(&pdev->dev, res);
> -	if (sdev->mmio == NULL)
> -		return -ENOMEM;
> +	if (IS_ERR(sdev->mmio))
> +		return PTR_ERR(sdev->mmio);
>  
>  	ret = shmob_drm_setup_clocks(sdev, pdata->clk_source);
>  	if (ret < 0)
>