From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48358) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fSinH-0004PB-8r for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:53:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fSinD-0008I0-B5 for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:53:03 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:46112 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fSinD-0008HH-6d for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:52:59 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1865D401EF30 for ; Tue, 12 Jun 2018 12:52:58 +0000 (UTC) Date: Tue, 12 Jun 2018 13:52:54 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20180612125254.GB2512@work-vm> References: <20180608130846.22234-1-dgilbert@redhat.com> <20180608130846.22234-6-dgilbert@redhat.com> <87y3flilan.fsf@dusky.pond.sub.org> <20180611174958.GP2661@work-vm> <20180612053720.pp2xvb7r34o6ort7@sirius.home.kraxel.org> <87k1r4use2.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k1r4use2.fsf@dusky.pond.sub.org> Subject: Re: [Qemu-devel] [PATCH v3 5/7] hmp: Add info commands for preconfig List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Gerd Hoffmann , imammedo@redhat.com, Eduardo Habkost , qemu-devel@nongnu.org * Markus Armbruster (armbru@redhat.com) wrote: > Gerd Hoffmann writes: > > > Hi, > > > >> > Now let's review the three commands: > >> > > >> > * Gerd, why does "info usbhost" have no QMP equivalent? > > > > Works only when running qemu directly, in the libvirt sandbox qemu > > hasn't the permissions needed to scan the host usb bus so that would be > > rather pointless ... > > I don't think this meets either of the two criteria: > > * I meets "makes no sense in QMP" only if QMP implies "can't scan host > USB bus". Libvirt implies it, but QMP doesn't imply libvirt; it's its > most important, not its sole user. > > * It meets "of use only for human users" only if we're convinced it's of > no use to programs. > > To avoid speculation and endless arguments about what could or could > not be of use, we've always stuck to "when in doubt, assume it could > be of use". > > "Libvirt can't use it" falls short. > > "Any management application worth anything would deny QEMU the > capability to scan the USB host bus, and thus wouldn't be able to use > it" is exactly the argument we intended to avoid. > > QMP falling short of completeness in relatively unimportant ways like > this one isn't exactly terrible. The most serious effect is probably > serving as a bad example that leads to further arguments like this one. > These are well worth avoiding, though. Markus: a) This is a separate discussion; info usbhost has been there for many years; this patch set doesn't change that. b) From HMP, if someone wants to add a command like 'info usbhost' to make their debugging of USB easy, then HMP is all for that and there's no way I'm going to require QMP implementations for a debug command. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK