From mboxrd@z Thu Jan 1 00:00:00 1970 From: Markus Armbruster Subject: Re: [Qemu-devel] Re: RFC qdev path semantics Date: Wed, 16 Jun 2010 16:31:51 +0200 Message-ID: References: <20100614054923.879.33717.stgit@localhost.localdomain> <201006161423.58499.paul@codesourcery.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: chrisw@redhat.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, Alex Williamson , avi@redhat.com, kraxel@redhat.com To: Paul Brook Return-path: Received: from mx1.redhat.com ([209.132.183.28]:38718 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753498Ab0FPOcD (ORCPT ); Wed, 16 Jun 2010 10:32:03 -0400 In-Reply-To: <201006161423.58499.paul@codesourcery.com> (Paul Brook's message of "Wed, 16 Jun 2010 14:23:57 +0100") Sender: kvm-owner@vger.kernel.org List-ID: Paul Brook writes: >> > Bus names are chosen by the system as follows: >> > >> > * If the driver of the parent device model provides a name, use that. >> > >> > * Else, if the parent device has id ID, use ID.NUM, where NUM is the bus >> > >> > number, counting from zero in creation order. >> > >> > * Else, use TYPE.NUM, where TYPE is derived from the bus type, and NUM >> > >> > is the bus number, as above. >> > >> > ### Paul proposes to drop ID.NUM. >> >> ABI change: "-device lsi,id=my-scsi -device scsi-disk,bus=my-scsi.0" no >> longer works. > > IMO this is a fundamentally broken ABI, so I don't care. Users of this ABI won't appreciate that attitude. I do support dropping ID.NUM, but we owe our users due ABI diligence. >> > ### Paul proposes to either drop TYPE.NUM (and require drivers to >> > provide bus names), or make NUM count separately for each bus type. >> >> Likewise. > > I'd be surprised if anyone actually uses absolute device paths at this time, > and they're probably going to be broken by other changes. Yes. > Using these default bus names as global identifiers is fixable using aliases > (e.g. -device lsi,bus=pci.0). I'd expect this to cover most interesting uses. > See http://lists.nongnu.org/archive/html/qemu-devel/2010-06/msg02149.html Keeping the old bus names work for the buses we create automatically shouldn't be hard. Only a few, and no ID.NUM there. It's the user-created buses that worry me. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=46289 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OOtev-0000Pz-Ez for qemu-devel@nongnu.org; Wed, 16 Jun 2010 10:32:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OOtet-0001yr-RP for qemu-devel@nongnu.org; Wed, 16 Jun 2010 10:32:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31106) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OOtet-0001yb-Kl for qemu-devel@nongnu.org; Wed, 16 Jun 2010 10:32:03 -0400 From: Markus Armbruster Subject: Re: [Qemu-devel] Re: RFC qdev path semantics References: <20100614054923.879.33717.stgit@localhost.localdomain> <201006161423.58499.paul@codesourcery.com> Date: Wed, 16 Jun 2010 16:31:51 +0200 In-Reply-To: <201006161423.58499.paul@codesourcery.com> (Paul Brook's message of "Wed, 16 Jun 2010 14:23:57 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: chrisw@redhat.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, Alex Williamson , kraxel@redhat.com, avi@redhat.com Paul Brook writes: >> > Bus names are chosen by the system as follows: >> > >> > * If the driver of the parent device model provides a name, use that. >> > >> > * Else, if the parent device has id ID, use ID.NUM, where NUM is the bus >> > >> > number, counting from zero in creation order. >> > >> > * Else, use TYPE.NUM, where TYPE is derived from the bus type, and NUM >> > >> > is the bus number, as above. >> > >> > ### Paul proposes to drop ID.NUM. >> >> ABI change: "-device lsi,id=my-scsi -device scsi-disk,bus=my-scsi.0" no >> longer works. > > IMO this is a fundamentally broken ABI, so I don't care. Users of this ABI won't appreciate that attitude. I do support dropping ID.NUM, but we owe our users due ABI diligence. >> > ### Paul proposes to either drop TYPE.NUM (and require drivers to >> > provide bus names), or make NUM count separately for each bus type. >> >> Likewise. > > I'd be surprised if anyone actually uses absolute device paths at this time, > and they're probably going to be broken by other changes. Yes. > Using these default bus names as global identifiers is fixable using aliases > (e.g. -device lsi,bus=pci.0). I'd expect this to cover most interesting uses. > See http://lists.nongnu.org/archive/html/qemu-devel/2010-06/msg02149.html Keeping the old bus names work for the buses we create automatically shouldn't be hard. Only a few, and no ID.NUM there. It's the user-created buses that worry me.