Re: [Qemu-devel] [RFC 00/11]: QMP feature negotiation support

[Jamie Lokier]

Daniel P. Berrange wrote:
> On Tue, Jan 26, 2010 at 12:57:54PM +0000, Jamie Lokier wrote:
> > Luiz Capitulino wrote:
> > > capability_enable [ "foo", "bar" ]
> > > 
> > >  Now, only one command is not terrible difficult, but we would
> > > have to accept an array of objects, like:
> > > 
> > > [ { "name": "foo", "enabled": true }, { "name": "bar", "enabled": true } ]
> > 
> > That looks like XML-itis.
> > 
> > Why not { "foo": true, "bar": true }?
> 
> It depends on whether we think we're going to need to add more metadata
> beyond just the enabled/disabled status. If we did want to add a further
> item against foo & bar, then having the array of hashes makes that 
> extension easier becaue you add easily add more key/value pairs to
> each.

Sure, extensibility is good, and I personally don't care which
format/function are used.  Just wanted to question the padded
structure, because sometimes that style is done unintentially.

Look at the argument leading up here - Luiz says let's use separate,
non-extensible enable/disable commands taking a list, because if it
were a single command it'd be important to make it extensible.  Does
that make sense?  I don't understand that reasoning.

On that topic: In the regular monitor, commands are often extensible
because they take command-line-style options, and you can always add
more options.  What about QMP - are QMP commands all future-extensible
with options in a similar way?

-- Jamie

(ps. XML-itis: a tendancy to write
<element><name>tag</name><attribute><attr-name>name</attr-name><attr-value>value</attr-value></attribute></element>,
when <tag name=value/> would do).