Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751652AbbEGUPE (ORCPT ); Thu, 7 May 2015 16:15:04 -0400 Received: from eddie.linux-mips.org ([148.251.95.138]:52308 "EHLO cvs.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751021AbbEGUO6 (ORCPT ); Thu, 7 May 2015 16:14:58 -0400 Date: Thu, 7 May 2015 21:14:54 +0100 (BST) From: "Maciej W. Rozycki" To: Peter Hurley cc: Robert Schwebel , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@pengutronix.de Subject: Re: earlycon: no match? In-Reply-To: <554B9F43.6000702@hurleysoftware.com> Message-ID: References: <20150503211054.GR15254@pengutronix.de> <55477BC1.6000805@hurleysoftware.com> <20150504194229.GR15254@pengutronix.de> <5547D4DB.8060300@hurleysoftware.com> <20150504205241.GT15254@pengutronix.de> <5547E447.9020604@hurleysoftware.com> <554B9F43.6000702@hurleysoftware.com> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2528 Lines: 61 On Thu, 7 May 2015, Peter Hurley wrote: > > What's the point of having two parameters as synonyms whose syntax is not > > compatible to each other in the general case? I'd expect the following > > cases to be handled: > > > > 1. Regular console only (no early console requested) => `console=foo...'. > > > > 2. Both early and regular console => `earlycon=blah... console=foo...'. > > > > 3. Early console handing over to regular console => `earlycon=blah...'. > > 4. Early console only => `earlycon=blah...' > > How to distinguish between 3 & 4? Good point. If you want to disable the handover, then it has to be handled by the early console driver somehow. Perhaps an option for `earlycon=' (e.g. `nohandover') would be required for that. In that case the default selection would apply for the regular console, depending on the available drivers. Your concern appears to me unrelated to `earlycon=' vs `console=' parameter aliasing though. The same observation about the handover applies whether the parameters are aliased to each other or not. Have I missed anything? > > Why do you want to support `console=blah...' too (a question to be asked > > back in 2007, but better late than never)? > > Command line is considered to be userspace, so it doesn't really matter > what I think about whether console= should have been overloaded like that. > > The fact is, it was. The change has not been cast in stone, it can always be reverted if on the second thoughts it is concluded to have been wrong. How does this overload interact with multiple `console=' options being present BTW, which one is considered the early console? Or do we support driving multiple early consoles in parallel just as we do with regular consoles? > > If you do need to support such aliasing, then I suggest that you complain > > about no early console match only if `earlycon=blah...' has been truly > > used and avoid the warning where `console=blah...' has been used instead > > (a warning about the latter can be issued where no regular console match > > happened). > > I'm tearing it out; I'd prefer to go back to the old way where you > don't know why your earlycon didn't start, and I don't get emails > complaining about logs. Up to you. Maciej -- 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/