Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753152Ab0HYJzo (ORCPT ); Wed, 25 Aug 2010 05:55:44 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:46191 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752696Ab0HYJzm (ORCPT ); Wed, 25 Aug 2010 05:55:42 -0400 Date: Wed, 25 Aug 2010 11:08:13 +0100 From: Alan Cox To: Greg KH Cc: Kay Sievers , Samo Pogacnik , linux kernel , linux-embedded Subject: Re: [PATCH] detour TTY driver - now ttyprintk Message-ID: <20100825110813.5f7d7ac8@lxorguk.ukuu.org.uk> In-Reply-To: <20100825004134.GA28884@suse.de> References: <20100625120329.1303aa61@lxorguk.ukuu.org.uk> <1282683470.8020.66.camel@itpsd6lap> <20100824211016.GA7176@suse.de> <1282687797.8020.108.camel@itpsd6lap> <20100824222035.GA10625@suse.de> <1282690232.8020.116.camel@itpsd6lap> <20100824225703.GA5913@suse.de> <20100825002221.68fc09a4@lxorguk.ukuu.org.uk> <20100824231241.GA6971@suse.de> <20100825005152.40ba2f12@lxorguk.ukuu.org.uk> <20100825004134.GA28884@suse.de> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1851 Lines: 45 > > Do you want to be able to flip between a real debug interface and a > > logging device on the same software set without risking changing behaviour > > I don't understand this point. A tty has a very specific set of behaviours simply by being a tty. Some applications rely upon them so being able to flip between the two interfaces is useful. > > Do you want to load a 70K daemon and an initrd or burn about 1.5K on a > > kernel interface ? > > I'd rather burn 0K on the one we have today :) So say "N" when configuring > Seriously, look at how Fedora 14 handles this, why can't you do the same > for embedded systems all from userspace, no additional code needed > anywhere. Its a whole set of extra processes and daemons and stuff, and minimally uses something like 70K even if its very compact (8K stack, 40K+ page tables, 16K of buffers, code, data) - oh and I forgot the fifo buffering and pty cost - so its near 100K. 1.5K v 100K - for something 1.5K of kernel code that anyone else can turn off and would be off by default ? On a lot of embedded systems you don't have all the stuff Fedora carts around. No modules, initrds, magic front end processes, graphical startup daemons etc, all of which work to produce that feature IFF you have pty support in your kernel, and for the current code also glibc. You also want errors to get out (or stored) even if there are crashes - which the Fedora one is not very good at. To be fair in the Fedora world its not a big deal to say 'Oh dear, boot with ....'. Embedded isn't the same, and you want to capture the odd rare error reliably. Alan -- 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/