From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:37822) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QUHtJ-0006Ko-Oy for qemu-devel@nongnu.org; Wed, 08 Jun 2011 08:29:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QUHtH-00012X-Vh for qemu-devel@nongnu.org; Wed, 08 Jun 2011 08:29:45 -0400 Received: from goliath.siemens.de ([192.35.17.28]:29500) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QUHtH-00011u-BG for qemu-devel@nongnu.org; Wed, 08 Jun 2011 08:29:43 -0400 Message-ID: <4DEF6B2B.7090305@siemens.com> Date: Wed, 08 Jun 2011 14:29:31 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1307532813-27175-1-git-send-email-peter.maydell@linaro.org> In-Reply-To: <1307532813-27175-1-git-send-email-peter.maydell@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC 0/3] basic support for composing sysbus devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Anthony Liguori , =?UTF-8?B?SnVoYSBSaWloaW3DpGtp?= , patches@linaro.org, qemu-devel@nongnu.org, Markus Armbruster , Paul Brook On 2011-06-08 13:33, Peter Maydell wrote: > At the moment you can't really implement one sysbus device by saying > that it's composed of a set of other sysbus devices. This patch adds > new functions sysbus_pass_mmio() and sysbus_pass_one_irq() which > allow a sysbus device to delegate an MMIO or IRQ to another sysbus > device (The approach is inspired by the existing sysbus_pass_irq() > which lets a sysbus device delegate all its IRQs at once). > > This works; the most obvious deficiency is that the subcomponent > device will still appear as its own device on the bus. > > So: is this a reasonable solution to the problem, or an unacceptable > hack? Comments welcome :-) Sounds more like a little hack. :) The relationships should be expressed via qdev, not yet another sysbus-specific extension. Generally, many services of sysbus should rather be generic qdev things. Is there anything that today prevents creating a local bus and attaching the component devices to that? If it's multi-bus support, that should to be added anyway. Passing-through of MMIO and IRQs is still a worthwhile generic service, then probably qbus associated. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux