Re: [Qemu-devel] [PATCH v5 2/5] arm: qmp: add query-gic-capabilities interface

[Peter Xu <peterx@redhat.com>]

On Tue, Mar 22, 2016 at 12:42:42PM -0600, Eric Blake wrote:
> On 03/17/2016 09:27 PM, Peter Xu wrote:
> > This patch adds the command "query-gic-capabilities" but not implemnet
> 
> s/not implemnet/does not implement/

Yep, again. Thanks.

> 
> > it. The command is ARM-only. Return of the command is a list of
> > GICCapability struct that describes all GIC versions that current QEMU
> > and system support.
> > 
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> 
> > +++ b/qapi-schema.json
> > @@ -4156,3 +4156,14 @@
> >    'data': { 'version': 'int',
> >              'emulated': 'bool',
> >              'kernel': 'bool' } }
> > +
> > +##
> > +# @query-gic-capabilities:
> > +#
> > +# Return a list of supported GIC version capabilities.
> > +#
> > +# Returns: a list of GICCapability.
> > +#
> > +# Since: 2.6
> > +##
> > +{ 'command': 'query-gic-capabilities', 'returns': ['GICCapability'] }
> 
> On the surface, this seems okay.  As mentioned before, I would have
> squashed 1 and 2 into a single patch.  The GICCapability type is
> extensible, and introspection is sufficient at seeing what the type is
> currently capable of exposing.
> 
> On the other hand...
> 
> > +++ b/scripts/qapi.py
> > @@ -46,6 +46,7 @@ returns_whitelist = [
> >      'query-tpm-models',
> >      'query-tpm-types',
> >      'ringbuf-read',
> > +    'query-gic-capability',
> 
> ...it required a whitelist, because you are violating the usual
> convention of returning a dict.  If you DO need the whitelist, your
> addition should have been kept sorted.  But you don't need it, if you
> would modify your QAPI to return a dict:
> 
> { 'struct': 'GICCapabilitiesReturn',
>   'data': { 'capabilities': ['GICCapability'] } }
> { 'command': 'query-gic-capabilities',
>   'returns': 'GICCapabilitiesReturn' }
> 
> Yes, the dict has only a single key, and that key points to the same
> list; but now you have future extensibility: in the future, we could
> return any future global data as a sibling to the array, without having
> to modify every element of the array to repeat redundant information.

Yes, I think this is better solution. Will adopt this in next version.

Thanks for the comments!

-- peterx