Re: [Qemu-devel] [PATCH v2] qom: Implement qom-get HMP command

["Daniel P. Berrange" <berrange@redhat.com>]

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:
> > 
> > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > >
> > > This started off as Andreas Färber'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>
> > 
> > Ignorant question: how does qom-set deal with structs?
> > 
> > I tried the obvious
> > 
> >     (qemu) qom-set /machine rtc-time abc
> >     Insufficient permission to perform this operation
> 
> 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
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|