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From: Arnd Bergmann <arnd@arndb.de>
To: "Russell King - ARM Linux" <linux@arm.linux.org.uk>
Subject: Re: [PATCH 1/4] gpiolib: introduce descriptor-based GPIO interface
Date: Wed, 9 Jan 2013 11:52:29 +0000
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Cc: linux-arch@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>,
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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