Re: [Qemu-devel] [PATCH v2 8/8] qapi: query-blockstat: add driver specific file-posix stats

[Eric Blake <eblake@redhat.com>]

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On 01/23/2018 05:28 AM, Anton Nefedov wrote:

>>> +
>>> +##
>>> +# @BlockDriverStats:
>>> +#
>>> +# Statistics of a block driver (driver-specific)
>>> +#
>>> +# Since: 2.12
>>> +##
>>> +{ 'union': 'BlockDriverStats',
>>> +  'data': {
>>> +      'file': 'BlockDriverStatsFile'
>>> +  } }
>>
>> Markus has been adamant that we add no new "simple unions" (unions with
>> a 'discriminator' field) - because they are anything but simple in the
>> long run.

> 
> Right, forgot about those unions.. Will fix.
> 
> (I guess I will need an extra enum, like BlockdevDriverWithStats with a
> single 'file' member, otherwise it seems to require to define data for
> each BlockdevDriver type)

Kevin also recently requested an easier way to make a flat union that
uses only a subset of a larger enum.  Maybe it's worth investing some
time in a QAPI generator patch to make this part easier (I have a
potential patch floating on one of my older branches that would allow
'branch':{} rather than having to declare a dummy type, but that's
slightly different than not even supplying the branches that you aren't
implementing).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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