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Date: Wed, 14 Sep 2016 11:48:31 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
Message-ID: <20160914104831.GH28399@redhat.com>
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	<87h99kdwha.fsf@dusky.pond.sub.org> <20160914103005.GA2852@work-vm>
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Subject: Re: [Qemu-devel] [PATCH v2] qom: Implement qom-get HMP command
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>, kwolf@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, arei.gonglei@huawei.com, pbonzini@redhat.com, afaerber@suse.de

On Wed, Sep 14, 2016 at 11:30:06AM +0100, Dr. David Alan Gilbert wrote:
> * Markus Armbruster (armbru@redhat.com) wrote:
> > "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> writes:
> >=20
> > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > >
> > > 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 <dgilbert@redhat.com>
> >=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 which
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 properties.

Regards,
Daniel
--=20
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