On 09/16/2015 01:11 AM, Wen Congyang wrote:
>>>> Possible workaround in the meantime - instead of trying to go with a
>>>> nice flat union (where all QMP keys are in the same {} level), we can
>>>> use nesting (structs that add another {} to include the unions).
>>>
>>> How to include the unions to a structs? Use 'base'?
>>
>> Conceptually, by adding a layer of nesting. On the wire, instead of:
>>
>> { "switch1":"value", "switch2":"value", "body2":"blah" }
>>
>> you would instead have:
>>
>> { "switch1":"value", "data": { "switch2":"value", "body2":"blah" } }
>>
>> Anywhere in qapi that you try to have:
>> { 'union': ..., 'data':{'switch1':'Union'}}
>>
>> you instead create a wrapper type:
>> { 'struct':'Wrapper', 'data':{'data':'Union'}}
>> { 'union': ..., 'data':{'switch1':'Wrapper'}}
>
> If so, the option is "data.switch1" not "switch1"
>
>>
>>
>> What I don't know is whether the extra QMP nesting makes it easier or
>> harder to support the existing NBD command line options, and it would
>
> Yes, it is harder to support it.All the more reason to push the qapi improvements through, so that qapi can expose a flat union and not make the command line have to go through ugly nesting. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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