Message-ID: <20060818130242.12410.qmail@lwn.net>
To: Rolf Eike Beer <eike-kernel@sf-tec.de>
Subject: Re: cdev documentation (was Drop second arg of unregister_chrdev()) 
From: corbet@lwn.net (Jonathan Corbet)
In-reply-to: Your message of "Fri, 18 Aug 2006 09:15:28 +0200."
             <200608180915.28763.eike-kernel@sf-tec.de> 
Cc: Alexey Dobriyan <adobriyan@gmail.com>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
Date: Fri, 18 Aug 2006 07:02:42 -0600
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1238
Lines: 30

Rolf Eike Beer <eike-kernel@sf-tec.de> wrote:

> Nevertheless, I ported my driver to the new interface. I see it cdev_add() 
> succeeding, but the device never shows up in sysfs. Do I have to do any more 
> tricks with class devices and stuff?

Yes, cdevs do not, themselves, show up in sysfs.  A simple class is what
you want for that part of the job.

> While I was sneaking around in the code I found this drivers/char/tty_io:3093
> 
>         cdev_init(&driver->cdev, &tty_fops);
>         driver->cdev.owner = driver->owner;
>         error = cdev_add(&driver->cdev, dev, driver->num);
>         if (error) {
>                 cdev_del(&driver->cdev);
> 
> Isn't the call to cdev_del() just wrong here?

It is correct, in that it returns the reference you hold to the cdev's
internal kobject.  If you got the cdev with cdev_alloc(), that's the
only way it will get returned to the system.  For a cdev allocated
elsewhere (as is the case here) it probably doesn't make any difference.

jon
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/