linux-kernel - Re: [PATCH] Fix debugfs_create_file's error checking method for usb/gadget/

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Date:	Fri, 17 Oct 2008 11:18:15 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Zhaolei <zhaolei@...fujitsu.com>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<dbrownell@...rs.sourceforge.net>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] Fix debugfs_create_file's error checking method for
 usb/gadget/

On Fri, 17 Oct 2008, Zhaolei wrote:

> Hi,
> 
> debugfs_create_file() returns NULL if an error occurs, returns -ENODEV
> when debugfs is not enabled in the kernel.
> 
> Signed-off-by: Zhao Lei <zhaolei@...fujitsu.com>
> ---
>  drivers/usb/gadget/s3c2410_udc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/usb/gadget/s3c2410_udc.c b/drivers/usb/gadget/s3c2410_udc.c
> index 29d13eb..4ba50ef 100644
> --- a/drivers/usb/gadget/s3c2410_udc.c
> +++ b/drivers/usb/gadget/s3c2410_udc.c
> @@ -1894,7 +1894,7 @@ static int s3c2410_udc_probe(struct platform_device *pdev)
>  		udc->regs_info = debugfs_create_file("registers", S_IRUGO,
>  				s3c2410_udc_debugfs_root,
>  				udc, &s3c2410_udc_debugfs_fops);
> -		if (IS_ERR(udc->regs_info)) {
> +		if (IS_ERR(udc->regs_info) || !udc->regs_info) {
>  			dev_warn(dev, "debugfs file creation failed %ld\n",
>  				 PTR_ERR(udc->regs_info));
>  			udc->regs_info = NULL;

In fact the original code and your patch are both wrong.  The test 
should simply be:

		if (!udc->regs_info) {
			dev_warn(dev, "debugfs file creation failed\n");

(The line setting udc->regs_info to NULL can then be removed.)

The driver should be able to work even if debugfs isn't enabled in the 
kernel.

Alan Stern

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