linux-kernel - Re: [PATCH] serial: DCC(JTAG) serial and console emulation support

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Message-ID: <1286483766.23836.39.camel@c-dwalke-linux.qualcomm.com>
Date:	Thu, 07 Oct 2010 13:36:06 -0700
From:	Daniel Walker <dwalker@...eaurora.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	"Hyok S. Choi" <hyok.choi@...sung.com>,
	Tony Lindgren <tony@...mide.com>,
	Jeff Ohlstein <johlstei@...cinc.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Ben Dooks <ben-linux@...ff.org>,
	Alan Cox <alan@...ux.intel.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Mike Frysinger <vapier@...too.org>,
	Feng Tang <feng.tang@...el.com>,
	Tobias Klauser <tklauser@...tanz.ch>,
	Jason Wessel <jason.wessel@...driver.com>,
	Philippe Langlais <philippe.langlais@...ricsson.com>
Subject: Re: [PATCH] serial: DCC(JTAG) serial and console emulation support

On Thu, 2010-10-07 at 21:50 +0100, Alan Cox wrote:
> > +	  Say Y here if you want to install DCC driver as a normal serial port
> > +	  /dev/ttyS0 (major 4, minor 64). Otherwise, it appears as /dev/ttyJ0
> > +	  (major 4, minor 128) and can co-exist with other UARTs, such as
> > +	  8250/16C550 compatibles.
> > +
> 
> NAK to both

Both what?

> ttyJ0 is 204,186 for "JTAG1 DCC protocol based serial"
> 
> so there is an existing name and minor allocation, which as you won't be
> using two of them should be quite usable.
> 
> If you want to be able to switch at runtime to pretend it is ttyS0 please
> deal with that in your user space. The same rules apply to you as have
> been applied to everyone else who has tried to implement this same crap
> in their uart driver too (we'd have it in about 30 by now otherwise)

I would agree if this wasn't strictly for debugging embedded devices in
difficult situations.. After talking to Mike, it's seems like it would
be useful to have this as a ttyS* specifically because embedded devices
won't always create a ttyJ* for you and ttyS* will likely already exist.

Daniel

-- 

Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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