linux-kernel - Re: [PATCH] usb: dwc3: debugfs: fix error check

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Date:	Tue, 31 Jan 2012 06:53:32 -0800
From:	Greg KH <greg@...ah.com>
To:	Felipe Balbi <balbi@...com>
Cc:	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: debugfs: fix error check

On Tue, Jan 31, 2012 at 02:03:51PM +0200, Felipe Balbi wrote:
> debugfs APIs will return two different error
> values depending on the situation:
> 
>  -> if debugfs isn't enabled in the kernel:
> 	it will return -ENODEV
> 
>  -> if debugfs is enabled in the kernel:
> 	it will return NULL
> 
> This means that blindly using IS_ERR() isn't
> enough and, in fact, will not work on a real
> error condition.
> 
> While we could be checking for a NULL pointer
> only because we only compile and link debugfs.o
> when CONFIG_DEBUG_FS is enabled, we decided
> to play it safe should any of the debugfs rules
> change over time.

The rules should not change over time, and if they do, any in-kernel
users will be fixed up.

This shouldn't be that hard, just check for NULL and move on if an error
happens, don't mess with the IS_ERR() stuff at all.

Look at how the USB core handles this, and use that logic.

thanks,

greg k-h
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