linux-kernel - Re: [PATCH -next v3 1/2] media: cec: remove redundant null pointer checks in cec_devnode

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Message-ID: <b4bb440e-3998-41df-93dd-d69012ca8a08@xs4all.nl>
Date: Fri, 11 Oct 2024 13:21:35 +0200
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Li Zetao <lizetao1@...wei.com>, mchehab@...nel.org,
 gregkh@...uxfoundation.org, ricardo@...liere.net, ruanjinjie@...wei.com
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v3 1/2] media: cec: remove redundant null pointer
 checks in cec_devnode_init()

On 10/09/2024 17:48, Li Zetao wrote:
> Since the debugfs_create_dir() never returns a null pointer, checking
> the return value for a null pointer is redundant. Remove this check
> since debugfs_create_file can handle IS_ERR pointers. At the same time,
> debugfs_create_dir returns ERR_PTR (-ENODEV) by default when
> CONFIG_DEBUG_FS=N, so there is no need for CONFIG_DEBUG_FS macro
> isolation.
> 
> Signed-off-by: Li Zetao <lizetao1@...wei.com>
> ---
> v2 -> v3: Drop the null pointer check for top_cec_dir
> v2: https://lore.kernel.org/all/20240907034400.3693797-1-lizetao1@huawei.com/
> v1 -> v2: Remove this check since debugfs_create_file can handle IS_ERR
> pointers. And drop the ifdef CONFIG_DEBUG_FS statement.
> v1: https://lore.kernel.org/all/20240903143607.2004802-1-lizetao1@huawei.com/
> 
>  drivers/media/cec/core/cec-core.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/drivers/media/cec/core/cec-core.c b/drivers/media/cec/core/cec-core.c
> index e0756826d629..2897283ebe72 100644
> --- a/drivers/media/cec/core/cec-core.c
> +++ b/drivers/media/cec/core/cec-core.c
> @@ -374,10 +374,6 @@ int cec_register_adapter(struct cec_adapter *adap,
>  	}
>  
>  	dev_set_drvdata(&adap->devnode.dev, adap);
> -#ifdef CONFIG_DEBUG_FS
> -	if (!top_cec_dir)
> -		return 0;
> -
>  	adap->cec_dir = debugfs_create_dir(dev_name(&adap->devnode.dev),
>  					   top_cec_dir);
>  
> @@ -388,7 +384,6 @@ int cec_register_adapter(struct cec_adapter *adap,
>  		return 0;
>  	debugfs_create_file("error-inj", 0644, adap->cec_dir, adap,
>  			    &cec_error_inj_fops);

This still has to remain under #ifdef CONFIG_DEBUG_FS, otherwise cec_error_inj_fops
is not defined. You can probably move the #ifdef to just before the debugfs_create_file
call above.

Regards,

	Hans

> -#endif
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(cec_register_adapter);
> @@ -439,13 +434,7 @@ static int __init cec_devnode_init(void)
>  		return ret;
>  	}
>  
> -#ifdef CONFIG_DEBUG_FS
>  	top_cec_dir = debugfs_create_dir("cec", NULL);
> -	if (IS_ERR_OR_NULL(top_cec_dir)) {
> -		pr_warn("cec: Failed to create debugfs cec dir\n");
> -		top_cec_dir = NULL;
> -	}
> -#endif
>  
>  	ret = bus_register(&cec_bus_type);
>  	if (ret < 0) {