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Date: Tue, 25 Feb 2014 09:30:44 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] QOM vs QAPI for QMP APIs
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To: Markus Armbruster <armbru@redhat.com>, Eric Blake <eblake@redhat.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>, qemu-devel@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>, Luiz Capitulino <lcapitulino@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Andreas Faerber <afaerber@suse.de>, Anthony Liguori <aliguori@amazon.com>

Il 25/02/2014 09:25, Markus Armbruster ha scritto:
>> > Haven't we already done that in the past?  For example, object-add
>> > currently takes an unspecified dictionary of options, where you would
>> > have to consult QOM documentation to learn what makes sense to send.
> My question isn't about where the command details are documented, or
> even whether they are documented.  It's about ABI promises, or lack
> thereof.  The general promise for QMP is we treat it as stable ABI.  If
> we add QMP commands to examine and manipulate QOM, doesn't that move all
> of QOM under the QMP ABI promise, unless we explicitly excempt it?

We did already exempt it, in general.  QOM is not declared stable.

However, there are parts (-object, and in 2.0 object_add/object-add) 
that are part of the QEMU API/ABI.  Now that we have a way to restrict 
which classes will be compatible (only classes that are UserCreatable 
can be created and thus will require backwards compatibility), we need 
to document those closses.

Paolo