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From: Anthony Liguori <aliguori@us.ibm.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org, armbru@redhat.com, lcapitulino@redhat.com,
	qiaonuohan@cn.fujitsu.com, pbonzini@redhat.com,
	Amos Kong <akong@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] full introspection support for QMP
Date: Wed, 03 Jul 2013 10:59:35 -0500	[thread overview]
Message-ID: <8761wrk520.fsf@codemonkey.ws> (raw)
In-Reply-To: <20130703150807.GC2784@dhcp-200-207.str.redhat.com>

Kevin Wolf <kwolf@redhat.com> writes:

> Am 02.07.2013 um 19:06 hat Anthony Liguori geschrieben:
>> Eric Blake <eblake@redhat.com> writes:
>> > On 07/02/2013 08:51 AM, Anthony Liguori wrote:
>> >> Amos Kong <akong@redhat.com> writes:
>> >> 
>> >>> Introduces new monitor command to query QMP schema information,
>> >>> the return data is a nested dict/list, it contains the useful
>> >>> metadata.
>> >>>
>> >>> we can add events definations to qapi-schema.json, then it can
>> >>> also be queried.
>> >>>
>> >>> Signed-off-by: Amos Kong <akong@redhat.com>
>> >> 
>> >> Maybe I'm being too meta here, but why not just return qapi-schema.json
>> >> as a string and call it as day?
>
> I know you don't agree with this, but as I mentioned several times
> before, I think the schema as returned by the introspection functions
> shouldn't contain what a qemu of this version _could_ in theory provide,
> but what this specific build actually _does_ provide. It shouldn't
> include things that are compiled out.

I really don't disagree with you here.  I just don't like having two
formats for the schema.

>> > I've also been the one arguing that the additional complexity (an array of
>> > {"name":"str","type":"str","optional":bool"}) is better for libvirt in
>> > that the JSON is then well-suited for scanning (it is easier to scan
>> > through an array where the key is a constant "name", and looking for the
>> > value that we are interested in, than it is to scan through a dictionary
>> > where the keys of the dictionary are the names we are interested in).
>> > That is, the JSON in qapi-schema.json is a nice compact representation
>> > that works for humans, but may be a bit TOO compact for handling via
>> > machines.
>> 
>> But adding a bunch of code to do JSON translation just adds a bunch of
>> additional complexity.
>> 
>> One reasonable compromise would be:
>> 
>> { "command": "foo", "arguments": { "name": "str", "id": "int" },
>>                     "optional": { "bar": "bool" } }
>
> This assumes that optional vs. mandatory is the only property we ever
> want to describe for fields. Eric's approach is much more future-proof.
> Let's keep the format of qapi-schema.json an implementation detail that
> we can change and extend when necessary.

It's always possible to add another argument that describes additional
information.

For instance:

{ "command": "foo",
  "arguments": { "name": "str", "id": "int" },
  "optional": { "bar": "bool" },
  "defaults": { "bar": false } }

That doesn't mean I think exposing defaults is good, but rather that
it's still possible to do this in a compact form.

Regards,

Anthony Liguori

>
> Kevin

  reply	other threads:[~2013-07-03 16:01 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-19 12:24 [Qemu-devel] [PATCH] full introspection support for QMP Amos Kong
2013-06-19 12:49 ` Amos Kong
2013-06-20 10:16   ` Amos Kong
2013-07-02 16:39   ` Eric Blake
2013-06-21  3:20 ` Luiz Capitulino
2013-07-02  8:37   ` Amos Kong
2013-07-02 14:20     ` Luiz Capitulino
2013-07-16 10:52       ` Amos Kong
2013-07-02 14:51 ` Anthony Liguori
2013-07-02 15:28   ` Eric Blake
2013-07-02 15:39     ` Daniel P. Berrange
2013-07-02 16:44       ` Eric Blake
2013-07-02 17:01         ` Paolo Bonzini
2013-07-02 17:06           ` Eric Blake
2013-07-02 18:27             ` Anthony Liguori
2013-07-04  3:54               ` Amos Kong
2013-07-02 18:21         ` Anthony Liguori
2013-07-02 20:00           ` Paolo Bonzini
2013-07-02 20:08             ` Eric Blake
2013-07-02 20:58             ` Anthony Liguori
2013-07-03  5:52               ` Paolo Bonzini
2013-07-03 12:54                 ` Anthony Liguori
2013-07-03 14:45                   ` Paolo Bonzini
2013-07-03 16:06                     ` Anthony Liguori
2013-07-04  7:53                       ` Paolo Bonzini
2013-07-11 13:37                   ` Amos Kong
2013-07-02 17:06     ` Anthony Liguori
2013-07-02 17:11       ` Eric Blake
2013-07-02 18:28         ` Anthony Liguori
2013-07-03 15:08       ` Kevin Wolf
2013-07-03 15:59         ` Anthony Liguori [this message]
2013-07-04  7:42           ` Kevin Wolf
2013-07-04  7:55           ` Paolo Bonzini

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