Re: [Qemu-devel] [PATCH 1/3] arm: gic: add GICType

[Markus Armbruster]

Peter Xu <address@hidden> writes:

> On Wed, Mar 02, 2016 at 02:59:57PM +0100, Markus Armbruster wrote:
>> Peter Xu <address@hidden> writes:
>> > What's "query-schema"? Is that a QMP command?
>> 
>> Yes.
>> 
>> More than you ever wanted to know:
>> http://events.linuxfoundation.org/sites/events/files/slides/armbru-qemu-introspection.pdf
>> https://www.youtube.com/watch?v=IEa8Ao8_B9o&list=PLW3ep1uCIRfyLNSu708gWG7uvqlolk0ep&index=28
>
> Thanks for the pointers and cool slides! It's a good thing to pick
> up. :-)
>
> It'll be cool we treat data as codes, and codes as data.
>
> I see that qapi-introspect branch is not there now. Is it merged to
> some other branch already? When will it be there in QEMU master
> (still not in, right?)? Just curious about it.

Merged in commit 9e72681.

Between the talk and the merge, query-schema got renamed to
query-qmp-schema.  Sometimes I relapse.  Sorry for the confusion!

>> > What I meant is that, we can define the following (for example):
>> >
>> > { 'struct': 'GICCapInfo',
>> >   'data': [
>> >     'version': 'int',
>> >     'emulated': 'bool',
>> >     'kernel': 'bool'] }
>> >
>> > And:
>> >
>> > { 'command': 'query-gic-capability',
>> >   'returns': ['GICCapInfo'] }
>> >
>> > So we can keep this schema as it is when new versions arrive. We
>> > can just push another element in.
>> 
>> To answer questions of the sort "can this QEMU version do X?", it's
>> often useful to tie X to a schema change that is visible in the result
>> of query-schema.
>
> Now I can understand. For this case, I guess both ways work, right?
> Considering that if "query-schema" is still not there, I'd still
> prefer the "array" solution. At least, it can keep the schema
> several lines shorter (as you have mentioned already, it's *big*
> enough :). Also, even we would have "query-schema", I would still
> prefer not change schema unless necessary. What do you think?

I can't say without understanding what the introspection question would
be.  That needs actual thought, which is in short supply, especially
before breakfast ;)