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Date: Sun, 8 Aug 2010 04:38:46 +0400
From: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] tty_io: add an API to get device corresponding to
 tty_struct
Message-ID: <20100808003846.GA9123@doriath.ww600.siemens.net>
References: <20100806165844.GB3364@suse.de>
 <1281174902-6298-1-git-send-email-dbaryshkov@gmail.com>
 <20100807123333.614169f1@lxorguk.ukuu.org.uk>
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On Sat, Aug 07, 2010 at 12:33:33PM +0100, Alan Cox wrote:
> On Sat,  7 Aug 2010 13:55:02 +0400
> Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> wrote:
> 
> > Some device drivers (mostly tty line disciplines) would like to have way
> > to get a struct device instancve corresponding to passed tty_struct. Add
> > respective API call.
> 
> Most of the kernel simply keeps a parent device pointer in the struct. If
> we have a lookup method then we'll simply end up with a struct device in
> each tty ldisc struct instead, and it will be harder to clean up later.

The proposed usage (at least what we did in the second patch and what
I did in IEEE 802.15.4 tty driver) is to use this device pointer to
set up parent node for all devices created on top of given tty port.

> I think I'd much rather see this set when the tty is created and always
> available. That would also let the whole tty layer use dev_err() and
> friends usefully ?

I was afraid of messing with tty layer in such way, as it's a bit too
complex for me.

Do you mean adding struct device pointer to struct tty_struct (easy),
or refactoring code so, that struct tty_struct contains embedded
struct device and uses it for refcounting & stuff?

-- 
With best wishes
Dmitry

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