linux-kernel - Re: should RTS init in serial core be tied to CRTSCTS

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Message-ID: <20070308142849.GC30023@flint.arm.linux.org.uk>
Date:	Thu, 8 Mar 2007 14:28:49 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Oleksiy Kebkal <kebkal@...il.com>
Cc:	Robin Getz <rgetz@...ckfin.uclinux.org>,
	Krzysztof Halasa <khc@...waw.pl>,
	Mike Frysinger <vapier.adi@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: should RTS init in serial core be tied to CRTSCTS

On Thu, Mar 08, 2007 at 03:23:49PM +0100, Oleksiy Kebkal wrote:
> 2007/3/8, Russell King <rmk+lkml@....linux.org.uk>:
> >On Thu, Mar 08, 2007 at 08:44:31AM -0500, Robin Getz wrote:
> >> On Wed 7 Mar 2007 16:30, Oleksiy Kebkal pondered:
> >> > 2007/3/7, Robin Getz <rgetz@...ckfin.uclinux.org>:
> >> > > Right - so the question is where to manage the default state? I was
> >> > > thinking in the resource might be a good idea, but there isn't 
> >really a
> >> > > good place for it. (You could re-use some bits if flags, but I think 
> >that
> >> > > would not be a good idea).
> >> >
> >> > /proc/tty/driver/uartN/settings?
> >> >
> >>
> >> That would let you change things are run time, but the problem is at boot
> >> time. A default setting needs to be set, so when things initialize, and 
> >proc
> >> does not exist yet, it is still set properly...
> >
> >I disagree.  "proc does not exist yet" - the only time that applies is
> >long before userspace as active.
> >
> >As I've said already, having a console on the same port as your application
> >program is just asking for trouble.  All bets are off - the kernel _will_
> >corrupt your data stream in random places.
> >
> >Don't do it - it will _NEVER_ be reliable.
> >
> >Never, ever, mix kernel consoles with application serial ports.
> 
> Ok. I understand now one of the sources of misunderstanding. I don't
> want to mix console and application serial port.

It's not a misunderstanding if you realise that email is threaded and
you _follow_ the individual threads.  Robin has a similar concern to
you but _additionally_ wants something that you don't.

So really to remove the "confusion" from this discussion you should
avoid trying to correct replies to Robin's emails.

> The other problem is how to open serial port with correct settings
> _after_ booting. In this case /proc could be applicable, isn't it?

Doubt it with todays opinions about /proc contents.  Probably more
appropriate in sysfs, if someone can be bothered to do the work
required to properly integrate tty and sysfs.

Don't look at me; I'm not doing very much with serial anymore.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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