linux-kernel - Re: [PATCH 1/4] gpiolib: introduce descriptor-based GPIO interface

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Message-Id: <201301091152.30047.arnd@arndb.de>
Date:	Wed, 9 Jan 2013 11:52:29 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	"Russell King - ARM Linux" <linux@....linux.org.uk>
Cc:	linux-arch@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Alexandre Courbot <acourbot@...dia.com>,
	Guenter Roeck <linux@...ck-us.net>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/4] gpiolib: introduce descriptor-based GPIO interface

On Wednesday 09 January 2013, Russell King - ARM Linux wrote:
>         d = debugfs_create_dir("pm_debug", NULL);
>         if (IS_ERR_OR_NULL(d))
>                 return PTR_ERR(d);
> 
> Well, covered above.  NULL is success here.

This one is actually worse, because in case of debugfs_create_dir,
a negative error code is documented to mean "success": The debugfs
functions intentionally return ERR_PTR(-ENODEV) when debugfs is
disabled so that any code checking for NULL pretends it is a valid
pointer, but that code is only allowed to pass this pointer into
other debugfs functions that are also stubbed out and never
dereference it.

	Arnd
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