linux-kernel - Re: [PATCH 3/4] usb: typec: fusb302: Fix debugfs issue

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Date:   Mon, 30 Apr 2018 06:34:03 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans de Goede <hdegoede@...hat.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 3/4] usb: typec: fusb302: Fix debugfs issue

On 04/30/2018 05:41 AM, Heikki Krogerus wrote:
> Removing the "fusb302" debugfs directory when unloading
> the driver. That allows the driver to be loaded more then
> ones.
> 
> This fixes an issue where the driver, if unloaded, can't be
> re-loaded, as the "fusb302" debugfs directory already
> exists. While here, removing useless condition when creating
> the debugfs directory.
> 
> Fixes: 76f0c53d08b9 ("usb: typec: fusb302: Move out of staging")
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
>   drivers/usb/typec/fusb302/fusb302.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/typec/fusb302/fusb302.c b/drivers/usb/typec/fusb302/fusb302.c
> index eba6bb890b17..0e5d0aa052f5 100644
> --- a/drivers/usb/typec/fusb302/fusb302.c
> +++ b/drivers/usb/typec/fusb302/fusb302.c
> @@ -218,11 +218,9 @@ static struct dentry *rootdir;
>   static int fusb302_debugfs_init(struct fusb302_chip *chip)
>   {
>   	mutex_init(&chip->logbuffer_lock);
> -	if (!rootdir) {
> -		rootdir = debugfs_create_dir("fusb302", NULL);
> -		if (!rootdir)
> -			return -ENOMEM;
> -	}

I think the idea here was to permit more than one instance of the driver,
and have all debugfs file entries under the fusb302 directory. Loading the
second instance will fail after this patch is applied.

> +	rootdir = debugfs_create_dir("fusb302", NULL);
> +	if (!rootdir)
> +		return -ENOMEM;
>   
>   	chip->dentry = debugfs_create_file(dev_name(chip->dev),
>   					   S_IFREG | 0444, rootdir,
> @@ -234,6 +232,7 @@ static int fusb302_debugfs_init(struct fusb302_chip *chip)
>   static void fusb302_debugfs_exit(struct fusb302_chip *chip)
>   {
>   	debugfs_remove(chip->dentry);
> +	debugfs_remove(rootdir); >   }
>   
>   #else
>