Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755886Ab3EJXc1 (ORCPT ); Fri, 10 May 2013 19:32:27 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:48204 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754418Ab3EJXc0 (ORCPT ); Fri, 10 May 2013 19:32:26 -0400 Date: Sat, 11 May 2013 00:29:55 +0100 From: Russell King - ARM Linux To: Greg KH Cc: Arnd Bergmann , Jean-Christophe PLAGNIOL-VILLARD , Srinivas KANDAGATLA , Viresh Kumar , Will Deacon , jslaby@suse.cz, Samuel Ortiz , Nicolas Pitre , linux-doc@vger.kernel.org, Stephen Gallimore , linux-serial@vger.kernel.org, Jason Cooper , devicetree-discuss@lists.ozlabs.org, Rob Herring , Stuart Menefy , Stephen Warren , Dong Aisheng , linux-arm-kernel@lists.infradead.org, Mark Brown , linux-kernel@vger.kernel.org Subject: Re: [RFC 1/8] serial:st-asc: Add ST ASC driver. Message-ID: <20130510232955.GY18614@n2100.arm.linux.org.uk> References: <1368022187-1633-1-git-send-email-srinivas.kandagatla@st.com> <20130508161527.GA28080@kroah.com> <201305081831.48566.arnd@arndb.de> <20130508163613.GA13761@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130508163613.GA13761@kroah.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1680 Lines: 36 On Wed, May 08, 2013 at 09:36:13AM -0700, Greg KH wrote: > On Wed, May 08, 2013 at 06:31:48PM +0200, Arnd Bergmann wrote: > > On Wednesday 08 May 2013, Greg KH wrote: > > > > just mention there is not hardware reason to not use the generic ttySx > > > > in place of ttyAS as we have only one IP that handle serial on this > > > > family of SoC > > > > > > > > personally I'll switch to ttySx > > > > > > Great, then you can use the same major/minor range as well, so there's > > > no more objection from me about this :) > > > > Does that work these days when you have kernel with multiple built-in > > uart drivers? > > It "should", as the major/minor registration should only happen when the > hardware is found, but I haven't tested it out, so I can't say for sure. serial stuff has never operated like that. More specifically, it's a limitation with the tty stuff that the way stuff works is that a tty driver can only drive a single bunch of contiguous minor numbers. No interleaving is allowed. That limitation has existed for years, and I don't see it going away. As long as that limitation exists, you can only ever have one serial driver driving a set of contiguous minor numbers. There has been an attempt to "work around" this by making the 8250 driver "special" which was a complete hack to get it to work. That was while I maintained this stuff and I outright refused to make one serial driver magically special. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/