Re: cdev documentation (was Drop second arg of unregister_chrdev())

[Rolf Eike Beer <eike-kernel@sf-tec.de>]

Jonathan Corbet wrote:
> Rolf Eike Beer <eike-kernel@sf-tec.de> wrote:
> > > Might this, instead, be an opportunity to get rid of the internal
> > > register_chrdev() and unregister_chrdev() calls in favor of the cdev
> > > interface?
> >
> > In this case I would suggest to add documentation to this functions first
> > to get people the chance to actually know how to use them.
>
> How's the following?  Quickly done but, I hope, useful.
>
> I've also put something more tutorial-oriented at:
>
> 	http://lwn.net/SubscriberLink/195805/b835f36d3b8ee266/
>
> This can be formatted up for the Documentation directory if so desired.

Thanks from the "other developer". What I would like to have is a function 
that gives me the next (or even a random) available number from my range. 
Currently I have to do it on my own AFAICS. 

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?

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?

Eike

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