linux-kernel - Re: [PATCH] drivers/hid: Fix debugfs_create_dir's error checking method for hid-core

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Date:	Tue, 18 Aug 2015 15:12:37 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Alexander Kuleshov <kuleshovmail@...il.com>
cc:	Henrik Rydberg <rydberg@...math.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/hid: Fix debugfs_create_dir's error checking
 method for hid-core

On Sat, 15 Aug 2015, Alexander Kuleshov wrote:

> The debugfs_create_dir() function returns NULL if an error occurs. This patch
> adds check of the result of the debufs_create_dir() execution in the
> hid_debug_register().
> 
> Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> ---
>  drivers/hid/hid-core.c  | 6 ++++--
>  drivers/hid/hid-debug.c | 3 +++
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index e6fce23..315a980 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -2599,8 +2599,10 @@ int hid_add_device(struct hid_device *hdev)
>  	ret = device_add(&hdev->dev);
>  	if (!ret)
>  		hdev->status |= HID_STAT_ADDED;
> -	else
> -		hid_debug_unregister(hdev);
> +	else {
> +		if (hdev->debug_dir)
> +			hid_debug_unregister(hdev);
> +	}
>  
>  	return ret;
>  }
> diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
> index 2886b64..80fa03d 100644
> --- a/drivers/hid/hid-debug.c
> +++ b/drivers/hid/hid-debug.c
> @@ -1223,6 +1223,9 @@ static const struct file_operations hid_debug_events_fops = {
>  void hid_debug_register(struct hid_device *hdev, const char *name)
>  {
>  	hdev->debug_dir = debugfs_create_dir(name, hid_debug_root);
> +	if (!hdev->debug_dir)
> +		return -ENOMEM;
> +

What sense does it make to return -ENOMEM from void function?

>  	hdev->debug_rdesc = debugfs_create_file("rdesc", 0400,
>  			hdev->debug_dir, hdev, &hid_debug_rdesc_fops);
>  	hdev->debug_events = debugfs_create_file("events", 0400,

Fixing this is ultimately a good thing, but why did you just pick 
debugfs_create_dir() and left the other, with the same issue 
(debugfs_create_file()) intact?

-- 
Jiri Kosina
SUSE Labs

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