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From: Wen Congyang <wency@cn.fujitsu.com>
Message-ID: <55F7975B.4050405@cn.fujitsu.com>
Date: Tue, 15 Sep 2015 11:58:19 +0800
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Subject: Re: [Qemu-devel] [PATCH v3 1/5] support nbd driver in blockdev-add
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To: Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Alberto Garcia <berto@igalia.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>, qemu block <qemu-block@nongnu.org>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, qemu devel <qemu-devel@nongnu.org>, "Dr. David Alan
	Gilbert" <dgilbert@redhat.com>, Gonglei <arei.gonglei@huawei.com>, Stefan Hajnoczi <stefanha@redhat.com>, Yang Hongyang <yanghy@cn.fujitsu.com>

On 09/15/2015 11:46 AM, Eric Blake wrote:
> On 09/14/2015 08:27 PM, Wen Congyang wrote:
>>> Building fails:
>>>   GEN   qmp-commands.h
>>> In file included from /work/src/qemu/qapi-schema.json:9:
>>> In file included from /work/src/qemu/qapi/block.json:6:
>>> /work/src/qemu/qapi/block-core.json:1844: Flat union 'BlockdevOptionsNBD' must have a string base field
>>> Makefile:286: recipe for target 'qmp-commands.h' failed
>>> make: *** [qmp-commands.h] Error 1
> 
> Yep, doesn't work until pending qapi patches land.

This patchset: qapi: QMP introspection?

> 
>>>
>>> What about this:
>>> { 'struct': 'BlockdevOptionsNBDBase',
>>>   'data': {  'transport': 'NBDTransport', 'export': 'str' } }
>>> { 'union': 'BlockdevOptionsNBD',
>>>   'base': 'BlockdevOptionsNBDBase',
>>>   'discriminator': 'transport',
>>>   'data': { 'unix': 'NBDUnix', 'tcp': 'NBDInet', 'udp': 'NBDInet' } }
>>
>> Another problem:
>> In file included from /work/src/qemu/qapi-schema.json:9:
>> In file included from /work/src/qemu/qapi/block.json:6:
>> /work/src/qemu/qapi/block-core.json:1866: Member 'nbd' of union 'BlockdevOptions' cannot use union type 'BlockdevOptionsNBD'
>> Makefile:286: recipe for target 'qmp-commands.h' failed
> 
> Yep. Artificial restriction; we hope to lift it soon, but don't have
> enough qapi patches in place for that one yet (I have not posted my work
> in progress to get us that far).
> 
> 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'?

Thanks
Wen Congyang

>