Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752587AbZIHWxQ (ORCPT ); Tue, 8 Sep 2009 18:53:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751284AbZIHWxP (ORCPT ); Tue, 8 Sep 2009 18:53:15 -0400 Received: from terminus.zytor.com ([198.137.202.10]:41364 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbZIHWxP (ORCPT ); Tue, 8 Sep 2009 18:53:15 -0400 Message-ID: <4AA6DF50.3030603@zytor.com> Date: Tue, 08 Sep 2009 15:48:48 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: Mauro Carvalho Chehab CC: LKML , Kay Sievers , Andrew Morton , Alan Cox , Greg Kroah-Hartman Subject: Re: [PATCH RFC] char/tty_io: fix legacy pty name when more than 256 pty devices are requested References: <20090908144942.76ddf0e7@caramujo.chehab.org> In-Reply-To: <20090908144942.76ddf0e7@caramujo.chehab.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1269 Lines: 33 On 09/08/2009 10:49 AM, Mauro Carvalho Chehab wrote: > > It is important to preserve the old nomenclature for tty/pty devices for the > first 256 devices, to avoid breakage on existing applications and with udev. > > So, in order to allow more pty devices, the nomenclature were extended for > the devices with minor 256 or above. For those, the nomenclature will be: > ttyf0000-ttfpffff (pty slave) > ptyf0000-ttyfffff (pty master) > This would seem to be a somewhat silly way to extend it, especially given the arbitrary artificial limit of just over 2^16 entries. If you're going to do this, I would suggest using the following namespace, as such: [pt]ty[p-za-e][0-9a-f]+ sprintf(name, "%cty%c%x", slave ? 't' : 'p', "pqrstuvwxyzabcde"[(index >> 4) & 15], ((index >> 4) & ~15) | (index & 15)); No arbitrary limits, and it still extends the existing namespace with some reasonable continuity. It means bits [7:4] are weirdly encoded, but we get straightforward backwards compatibility as a result. -hpa -- 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/