From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:52278) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QV26s-00085b-2I for qemu-devel@nongnu.org; Fri, 10 Jun 2011 09:50:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QV26q-00048o-4f for qemu-devel@nongnu.org; Fri, 10 Jun 2011 09:50:49 -0400 Received: from mail-pv0-f173.google.com ([74.125.83.173]:32796) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QV26p-00048k-Pw for qemu-devel@nongnu.org; Fri, 10 Jun 2011 09:50:47 -0400 Received: by pvg3 with SMTP id 3so1285929pvg.4 for ; Fri, 10 Jun 2011 06:50:46 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4DF21F97.4070709@siemens.com> References: <1307532813-27175-1-git-send-email-peter.maydell@linaro.org> <4DEF6B2B.7090305@siemens.com> <4DF0FCDA.5070804@siemens.com> <4DF21334.2070204@us.ibm.com> <4DF21F97.4070709@siemens.com> Date: Fri, 10 Jun 2011 14:50:46 +0100 Message-ID: From: Peter Maydell Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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: Jan Kiszka Cc: Anthony Liguori , =?UTF-8?Q?Juha_Riihim=C3=A4ki?= , "patches@linaro.org" , "qemu-devel@nongnu.org" , Markus Armbruster , Paul Brook On 10 June 2011 14:43, Jan Kiszka wrote: > On 2011-06-10 15:10, Peter Maydell wrote: >> This makes the wiring of this signal look like a property of the >> isa-serial device, which is a bit odd, since it's just as much >> a property of the piix3. Actually it's neither, it's a property >> of the machine model, and you might actually want a syntax a bit >> more like: >> >> =C2=A0piix3 =3D piix3(property=3Dvalue, property=3Dvalue...); >> =C2=A0serial =3D isa-serial(property=3Dvalue...); >> =C2=A0connect(serial.irq, piix3.irq[3]); > > In fact, in the ISA case, it is a device property: The device, and only > the device decides which IRQ to use - from the bus it is attached to. So > attaching an ISA device to the bus of an ISA bridge like the PIIX3 and > selecting local IRQ 3 are the steps we can already express today. Ah, in that case Anthony's suggestion of -device piix3,id=3Dpiix3 -device isa-serial,id=3Dserial,irq=3Dpiix3.irq[3= ] wrong in a different way -- the isa-serial shouldn't care what other device is providing the ISA bus it is sitting on, it just has a property of which ISA irq line it is using (and rely on an isa bus abstraction to wire things up at the machine model level). [As you say, this works now.] But I think that's a non-typical case compared to the usual one of "these wires are just hardwired this way by the machine". -- PMM