linux-kernel - Re: [PATCH] gpiolib: fix device

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Date:	Tue, 3 Nov 2009 16:02:00 -0800
From:	Greg KH <greg@...ah.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sergei Shtylyov <sshtylyov@...mvista.com>,
	linux-kernel@...r.kernel.org, david-b@...bell.net,
	Kay Sievers <kay.sievers@...y.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] gpiolib: fix device_create() result check

On Tue, Nov 03, 2009 at 02:44:01PM -0800, Andrew Morton wrote:
> On Tue, 20 Oct 2009 20:35:23 +0400
> Sergei Shtylyov <sshtylyov@...mvista.com> wrote:
> 
> > In case of failure, device_create() returns not NULL but the error code.
> > The current code checks for non-NULL though which causes kernel oops in
> > sysfs_create_group() when device_create() fails.  Check for error using
> > IS_ERR() and propagate the error value using PTR_ERR() instead of fixed
> > -ENODEV code returned now...
> 
> Does anyone notice any missing information here?
> 
> /**
>  * device_create - creates a device and registers it with sysfs
>  * @class: pointer to the struct class that this device should be registered to
>  * @parent: pointer to the parent struct device of this new device, if any
>  * @devt: the dev_t for the char device to be added
>  * @drvdata: the data to be added to the device for callbacks
>  * @fmt: string for the device's name
>  *
>  * This function can be used by char device classes.  A struct device
>  * will be created in sysfs, registered to the specified class.
>  *
>  * A "dev" file will be created, showing the dev_t for the device, if
>  * the dev_t is not 0,0.
>  * If a pointer to a parent struct device is passed in, the newly created
>  * struct device will be a child of that device in sysfs.
>  * The pointer to the struct device will be returned from the call.
>  * Any further sysfs files that might be required can be created using this
>  * pointer.
>  *
>  * Note: the struct class passed to this function must have previously
>  * been created with a call to class_create().
>  */
> 
> 
> Why do we do this to ourselves?

Because we suck at writing documentation?  :)

Patches to add the one line:
	"If an error happens, a PTR_ERR is returned instead of a pointer
	to the device"
would be appreciated.

And yes, I like Alan's idea, that would be much nicer overall for lots
of functions like this.

thanks,

greg k-h
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