Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754523Ab3DVDK6 (ORCPT ); Sun, 21 Apr 2013 23:10:58 -0400 Received: from mail-vb0-f45.google.com ([209.85.212.45]:62229 "EHLO mail-vb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754133Ab3DVDK5 (ORCPT ); Sun, 21 Apr 2013 23:10:57 -0400 MIME-Version: 1.0 In-Reply-To: <87ehe3bbsm.fsf@rustcorp.com.au> References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <87wqs02uws.fsf@rustcorp.com.au> <87ehe3bbsm.fsf@rustcorp.com.au> Date: Mon, 22 Apr 2013 08:40:56 +0530 Message-ID: Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console devices. From: Anup Patel To: Rusty Russell Cc: Pranavkumar Sawargaonkar , "kvmarm@lists.cs.columbia.edu" , linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org, patches@linaro.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1785 Lines: 45 On 22 April 2013 06:51, Rusty Russell wrote: > > Pranavkumar Sawargaonkar writes: > > 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. > > But implementing virtio inside a bootloader has already been done for > coreboot, for example. A bootloader probably wants a virtio block > device, so a console is trivial. > > A single writable field for debugging makes sense. Anything more is far > less certain. The early read can be handy for bootloader who don't want to implement complete VirtIO programming. IMHO, early read would be totally optional for host and will not introduce any new config register so it is good to have in VirtIO console spec. Also, without early read the read behavior of early_rw field would be undefined in VirtIO console spec. > > Thanks, > Rusty. Best Regards, Anup -- 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/