Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932385Ab3DVOvF (ORCPT ); Mon, 22 Apr 2013 10:51:05 -0400 Received: from cantor2.suse.de ([195.135.220.15]:33431 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755037Ab3DVOvB convert rfc822-to-8bit (ORCPT ); Mon, 22 Apr 2013 10:51:01 -0400 Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console devices. Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: text/plain; charset=us-ascii From: Alexander Graf In-Reply-To: Date: Mon, 22 Apr 2013 16:50:58 +0200 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 Content-Transfer-Encoding: 8BIT Message-Id: <88344511-0EFA-4EA1-9793-5D25E8DA8239@suse.de> References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <87wqs02uws.fsf@rustcorp.com.au> <87ehe3bbsm.fsf@rustcorp.com.au> To: Anup Patel X-Mailer: Apple Mail (2.1278) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2195 Lines: 59 On 22.04.2013, at 05:10, Anup Patel wrote: > 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. Virtio is trivial. Seriously. Don't invent new secondary interfaces to the same thing just because you're afraid to write 5 lines of code instead of 2. Alex > > 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 > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm -- 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/