From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754366Ab0IVSWu (ORCPT ); Wed, 22 Sep 2010 14:22:50 -0400 Received: from g1t0026.austin.hp.com ([15.216.28.33]:13502 "EHLO g1t0026.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751967Ab0IVSWt (ORCPT ); Wed, 22 Sep 2010 14:22:49 -0400 From: Bjorn Helgaas To: "H. Peter Anvin" Subject: Re: Early console confusion Date: Wed, 22 Sep 2010 12:21:59 -0600 User-Agent: KMail/1.13.2 (Linux/2.6.32-24-generic; KDE/4.4.2; x86_64; ; ) Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, yinghai@kernel.org, just.for.lkml@googlemail.com, tglx@linutronix.de, hpa@linux.intel.com, Feng Tang , Alan Cox , greg@kroah.com References: <4C7B0578.8090807@kernel.org> <201009221044.58735.bjorn.helgaas@hp.com> <4C9A3487.6080005@zytor.com> In-Reply-To: <4C9A3487.6080005@zytor.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201009221222.00475.bjorn.helgaas@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, September 22, 2010 10:53:27 am H. Peter Anvin wrote: > On 09/22/2010 09:44 AM, Bjorn Helgaas wrote: > > > > If we don't like "uart8250,io,0x3f8" (which I agree is awfully clunky), > > we could easily add something like "console=com1" which encapsulated > > the well-defined PC concept. > > console=ttyS0 ... already works fine. Yes, but it doesn't give you early output. You have to wait until the 8250 driver loads and figures out which device will be ttyS0. If we use "console=tty0" or "console=ttyS0", those are device names that don't work until the driver is loaded. But if we specify the device explicitly, via "uart8250", "com1", "hsu", "vga", etc., we can make the console work early using a minimal driver, then switch to the regular driver later. The question is whether that would be good enough to let us remove the "earlycon=" and "earlyprintk=" stuff. > But yes, it's ugly and we have bass-ackwards compatibility problem... I think earlycon and earlyprintk have minimal backwards compatibility problems, since they're mostly for developers. And if we decided we did need to keep them, they could be undocumented and implemented on top of "console=" with the appropriate explicit device. I guess this is all just hot air since I don't have time to actually produce any patches :-( Bjorn