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

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Message-ID: <2024091142-flattery-graveyard-cfea@gregkh>
Date: Wed, 11 Sep 2024 07:30:31 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Li Zetao <lizetao1@...wei.com>
Cc: hverkuil-cisco@...all.nl, mchehab@...nel.org, ricardo@...liere.net,
	ruanjinjie@...wei.com, 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 Tue, Sep 10, 2024 at 11:48:02PM +0800, 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);
> -#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);

I'm going to be a pain here, and say "why do you need top_cec_dir at
all?"

Why not just look it up every time you want it after creating it with a
call to debugfs_lookup() or debugfs_lookup_and_remove()?

anyway, not a big deal, it's up to the maintainers here to want this as
well, just a thought for further calls cleanup work.

thanks,

greg k-h