Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965752Ab3DRIog (ORCPT ); Thu, 18 Apr 2013 04:44:36 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38417 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935341Ab3DRIoe convert rfc822-to-8bit (ORCPT ); Thu, 18 Apr 2013 04:44:34 -0400 References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <87wqs02uws.fsf@rustcorp.com.au> Mime-Version: 1.0 (1.0) In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Message-Id: <47354634-CA37-47E3-99D2-D4DDB08A9870@suse.de> Cc: Rusty Russell , "linaro-kernel@lists.linaro.org" , "patches@linaro.org" , "linux-kernel@vger.kernel.org" , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" X-Mailer: iPhone Mail (10B142) From: Alexander Graf Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console devices. Date: Thu, 18 Apr 2013 10:44:32 +0200 To: Pranavkumar Sawargaonkar Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1458 Lines: 33 Am 18.04.2013 um 09:32 schrieb Pranavkumar Sawargaonkar : > On 18 April 2013 12:21, Rusty Russell wrote: >> >> PranavkumarSawargaonkar writes: >>> From: Pranavkumar Sawargaonkar >>> >>> This patch implements early printk support for virtio-mmio console devices without using any hypercalls. >> >> This makes some sense, though not sure that early console *read* makes >> much sense. I can see the PCI version of this being useful as well. > > Read can be useful for "mach-virt" which will have only virtio console > as a console device. Then if someone wants to have UEFI or any other > boot-loader emulation, which expects user to input few things, in that > case read might become handy. A boot loader should easily be able to implement virtio-console for real. In fact, you should be able to do a simple virtio-console implementation for early printk too, that polls the host for acks rather than use interrupts. Check out my s390-zipl code for reference. I use that there. The advantage to that would be that no host changes are required whatsoever and the interface strictly stays as it is. Alex -- 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/