From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christopher Covington Subject: Re: what should a virtio-mmio transport without a backend look like? Date: Mon, 24 Jun 2013 08:26:26 -0400 Message-ID: <51C83AF2.5080404@codeaurora.org> References: <1371726501.3231.22.camel@hornet> <51C2FC5B.7080406@codeaurora.org> <51C4792F.6010709@codeaurora.org> <1371833230.3155.19.camel@hornet> <51C494EF.4060509@codeaurora.org> <51C49F52.1070906@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Peter Maydell Cc: =?UTF-8?B?S09OUkFEIEZyw6lkw6lyaWM=?= , Pawel Moll , "virtualization@lists.linux-foundation.org" List-Id: virtualization@lists.linuxfoundation.org On 06/22/2013 06:51 AM, Peter Maydell wrote: > On 21 June 2013 19:45, Christopher Covington wrote: >> You were proposing to use a valid/existing MagicValue/Version/VendorID with a >> special DeviceID that does nothing. I'm saying why not use a valid/existing >> MagicValue/Version/VendorID/DeviceID with a special parameter setting, size=0, >> that does nothing? [...] > Also, it's mixing a detail of the backend layer (what > a zero-sized disk happens to look like) with the transport layer, > which seems a bit ugly spec-wise. I don't think that has to be the case. From what I understand of your architecture, the device layer is completely opaque to the transport layer, and the transport layer is immutable, but surely the device layer will at least know how many transports are available? As long as that's true, can't the device layer just create real devices and hook them up to transports, and then create no-op devices and hook them up to any remaining transports? > (Implementation wise I'm not crazy about it either since it would > be way more complicated than saying "no backend? OK, RAZ/WI".) (I thought virtio block devices were already implemented.) Christopher -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation.