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

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> 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/
>
>> 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 <address@hidden>
>> ---
>
>> +++ 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.

I just tested it, the whitelist entry is superfluous, check_command()
accepts a list of dicts just fine.