From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48109) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blx9e-0002JT-BK for qemu-devel@nongnu.org; Mon, 19 Sep 2016 07:54:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1blx9Z-0005YL-N4 for qemu-devel@nongnu.org; Mon, 19 Sep 2016 07:54:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48586) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blx9Z-0005Y3-Dj for qemu-devel@nongnu.org; Mon, 19 Sep 2016 07:54:29 -0400 Date: Mon, 19 Sep 2016 12:54:24 +0100 From: "Daniel P. Berrange" Message-ID: <20160919115424.GM15201@redhat.com> Reply-To: "Daniel P. Berrange" References: <1473157086-12062-1-git-send-email-dgilbert@redhat.com> <87h99kdwha.fsf@dusky.pond.sub.org> <20160914103005.GA2852@work-vm> <20160914104831.GH28399@redhat.com> <87d1k0l036.fsf@dusky.pond.sub.org> <20160919095449.GJ15201@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160919095449.GJ15201@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] qom: Implement qom-get HMP command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: kwolf@redhat.com, qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , lcapitulino@redhat.com, arei.gonglei@huawei.com, pbonzini@redhat.com, afaerber@suse.de On Mon, Sep 19, 2016 at 10:54:49AM +0100, Daniel P. Berrange wrote: > On Mon, Sep 19, 2016 at 11:18:05AM +0200, Markus Armbruster wrote: > > "Daniel P. Berrange" writes: > >=20 > > > On Wed, Sep 14, 2016 at 11:30:06AM +0100, Dr. David Alan Gilbert wr= ote: > > >> * Markus Armbruster (armbru@redhat.com) wrote: > > >> > "Dr. David Alan Gilbert (git)" writes: > > >> >=20 > > >> > > From: "Dr. David Alan Gilbert" > > >> > > > > >> > > This started off as Andreas F=C3=A4rber's implementation from > > >> > > March 2015, but after feedback from Paolo morphed into > > >> > > using the json output which handles structs reasonably. > > >> > > > > >> > > Use with qom-list to find the members of an object. > > >> > > > > >> > > (qemu) qom-get /backend/console[0]/device/vga.rom[0] size > > >> > > 65536 > > >> > > (qemu) qom-get /machine smm > > >> > > "auto" > > >> > > (qemu) qom-get /machine rtc-time > > >> > > { > > >> > > "tm_year": 116, > > >> > > "tm_sec": 0, > > >> > > "tm_hour": 9, > > >> > > "tm_min": 46, > > >> > > "tm_mon": 8, > > >> > > "tm_mday": 6 > > >> > > } > > >> > > (qemu) qom-get /machine frob > > >> > > Property '.frob' not found > > >> > > > > >> > > Signed-off-by: Dr. David Alan Gilbert > > >> >=20 > > >> > Ignorant question: how does qom-set deal with structs? > > >> >=20 > > >> > I tried the obvious > > >> >=20 > > >> > (qemu) qom-set /machine rtc-time abc > > >> > Insufficient permission to perform this operation > > >>=20 > > >> I don't think it does. > > > > > > Indeed it can't - qom_set ends up calling object_property_parse whi= ch > > > uses string-input-visitor to parse the value, which can only handle > > > scalars as the magic special case list-of-ints. > > > > > > To deal with compound properties would really require us to use a > > > qdict_crumple + qmp_input_visitor combination, similar to how I've > > > made -object and object_add be able to deal with compound propertie= s. > >=20 > > HMP I/O formats are not ABI. We can use visitors in whatever way we > > want, as long as we keep -get and -set consistent. The sane way to d= o > > that is using the same kind of visitor for both, in its input and out= put > > form, respectively. > >=20 > > Right now, qom-set uses the string input visitor. As long as it does > > that, qom-get should use the string output visitor. Sadly, this pair= of > > visitors is quite limited ("does not implement support for visiting Q= API > > structs, alternates, null, or arbitrary QTypes"). We can extend it t= o > > cover more, or we can switch to another, less limited pair of visitor= s. > >=20 > > Can we agree on what to do so we can have qom-get sooner rather than > > later? It doesn't have to be perfect, we can iterate. >=20 > I think that -object sets the precedent that the rest should ultimately > follow. It currently uses the opts visitor syntax, but is being switche= d > over to the combination of qdict_crumple + qobject input visitor, which > is basically the same as opts visitor syntax for scalars and with dotte= d > notation for compound types. >=20 > The HMP object_add command will use the exact same syntax as -object > CLI arg. Given this, I think 'qom-set' really ought to be updated to us= e > qdict_crumple + qobject input visitor too, so it can deal with compound > types. In fact I'd view the lack of conversion of qom-set as a mistake > in my patch series - I should have converted that too, while adding > support for compound properties to -object and object_add. >=20 > This ultimately means that qom-get probably ought to use qobject output > visitor, followed by a qdict flatten operation to turn the nested > dicts/lists, into a flat dict with dotted syntax. Further, QOM has two methods which are intended to be mirror imges of each other - object_property_parse and object_property_print. The current qom-set impl uses object_property_parse, so we ought to make 'qom-get' use object_property_print. We would still need to enhance object_property_print() to deal with compound types, but that's doesn't have to be a blocker - Dave's qom-get patch can just use object_property_print() as it exists today and we can enhance the impl separately. Regards, Daniel --=20 |: http://berrange.com -o- http://www.flickr.com/photos/dberrange= / :| |: http://libvirt.org -o- http://virt-manager.or= g :| |: http://autobuild.org -o- http://search.cpan.org/~danberr= / :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vn= c :|