linux-kernel - Re: [PATCH 07/16] TTY: quatech2, remove unneeded is

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Date:	Wed, 13 Mar 2013 15:17:44 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Bill Pemberton <wfp5p@...idian.itc.virginia.edu>
CC:	gregkh@...uxfoundation.org, peter@...leysoftware.com,
	jirislaby@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/16] TTY: quatech2, remove unneeded is_open

On 03/13/2013 02:46 PM, Bill Pemberton wrote:
> Jiri Slaby writes:
>>
>> tty->ops->break_ctl cannot be called outside the gap between open and
>> close. So there is no need to check whether the port is open in
>> break_ctl in quatech2. Remove the check and also that member
>> completely.
>>
> 
> We can't get rid of is_open.  The devices use 1 read urb for all ports
> and will send various things about ports that haven't actually been
> opened.  So the driver needs to know if a port has actually been
> opened or not.  In fact, I was about to send a patch that fixes a
> warning caused by commit 2e124b4a390ca85325fae75764bef92f0547fa25
> causing the driver to try to write to ttys that weren't actually
> opened.

As long as tty_port exists for the port, calling tty buffer functions is
OK. The warning you mention is now bogus and there is a patch flying
around to disable that at the moment.

It is also that is_open was completely racy, right?

> The guard in qt2_break_ctl() can still be removed.

Ok.

thanks,
-- 
js
suse labs
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