From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk (caramon.arm.linux.org.uk [217.147.92.249]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 9F994DDF4E for ; Thu, 5 Apr 2007 04:15:54 +1000 (EST) Date: Wed, 4 Apr 2007 19:15:32 +0100 From: Russell King To: Theodore Tso , "H. Peter Anvin" , David Miller , dwmw2@infradead.org, paulus@samba.org, alan@lxorguk.ukuu.org.uk, flar@allandria.com, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Stop pmac_zilog from abusing 8250's device numbers. Message-ID: <20070404181531.GA9388@flint.arm.linux.org.uk> References: <1175663999.2932.8.camel@shinybook.infradead.org> <17939.15726.114059.679277@cargo.ozlabs.ibm.com> <1175666635.2932.17.camel@shinybook.infradead.org> <20070404.011208.120446173.davem@davemloft.net> <20070404083803.GA13134@flint.arm.linux.org.uk> <20070404122154.GF31973@thunk.org> <4613CF6A.2090407@zytor.com> <20070404174153.GI31973@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20070404174153.GI31973@thunk.org> Sender: Russell King List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Apr 04, 2007 at 01:41:53PM -0400, Theodore Tso wrote: > On Wed, Apr 04, 2007 at 09:16:42AM -0700, H. Peter Anvin wrote: > > One option would be to move the 8250-based serial ports, to, say, > > /dev/ttyN* (for National Semiconductors -- the best I could come up > > with) and redefine /dev/ttyS* as a serial port multiplexer which maps in > > all the types, for the ones that really want dynamic mapping. > > > Of course, now you have the potential of aliasing, again, which tends to > > cause all kinds of headaches w.r.t. locking. > > That would break the 99.9% of the the world using Intel-based systems > which only have 8250's, for very little gain. > > Like it or not, /dev/ttySx and 8250 UART's are to serial ports what > the PCI is to system buses.... And the simple answer to this (oh I've been here before) is to leave the existing serial allocations well alone. Then, you allocate a new major number and device name for the dynamically assigned space and arrange for the serial layer to map these new chardevs to the real serial ports. *However* you still run into the issue that you do not know how many serial ports you will need to register a tty driver with the tty layer. Solve that technical problem and the idea of having a single namespace for chosen serial ports and 8250 ports suddenly becomes realistic. Continue ignoring that problem and this thread will just grow with zero real progress. I'm repeating myself though. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: