linux-kernel - Re: How do I choose an arbitrary minor number for my tty device?

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Message-ID: <20101123230359.3c805e2e@lxorguk.ukuu.org.uk>
Date:	Tue, 23 Nov 2010 23:03:59 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Timur Tabi <timur@...escale.com>
Cc:	Greg KH <gregkh@...e.de>, Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Scott Wood <scottwood@...escale.com>,
	Stuart Yoder <stuart.yoder@...escale.com>
Subject: Re: How do I choose an arbitrary minor number for my tty device?

> Are you talking about this:
> 
> static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
> {
> 	*index = co->index;
> 
> 	return ehv_bc_driver;
> }

Yes.

> I never really understood this function, but almost everyone does the same
> thing, and it seems to work for me.  Looking at console_device(), it appears
> that all of the xxx_console_device functions are called in order until one of
> them returns non-NULL.

*index is the minor number to use - so you can return whichever minor
matches your primary interface

> > I suspect in your case you probably want to attach the primary byte
> > channel to minor 0 in the driver (and reserve it for that), or some
> > similar rule.
> 
> Yes, that's a good idea.  It does simplify things a lot.

It's probably the cleanest and simplest solution and it fits the
"natural" order of things.
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