Re: [Qemu-devel] [libvirt] [PULL 04/14] audio: -audiodev command line option basic implementation

[Eric Blake]

On 3/28/19 2:32 PM, Markus Armbruster wrote:

>>> Adding Markus to CC so we can figure out how to wire up the
>>> introspection for such command line options.
>>
>> query-command-line-options has always been woefully incomplete.  Sadly,
>> my replacement is still not ready.
>>
>> A reliable "witness" could serve a stop gap.  Unfortunately,
>> query-qmp-schema doesn't provide one: the series does not change
>> generated qapi-introspect.c.
>>
>> Need to think some more.
> 
> There is no witness in query-qmp-schema.


> 5. Screw it, create a new query command to return just the information
>    from qemu_options[].
> 
> Alternatives 1. to 3. break ABI in different ways.  Finding out which of
> the ABI breaks upset libvirt would be easy enough.  But even if one of
> them is fine with libvirt, ABI breaks are best avoided.  Risking one in
> 4.0 is out of the question, we're far too late in the cycle.
> 
> Alternative 5. feels simpler than 4., and is similarly ugly.  This might
> still be acceptable (barely) for 4.0.
> 
> Opinions?

Alternative 6:

Don't worry about patching q-c-l-o, but instead patch query-qemu-features:

https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg07584.html

Add a new feature: audiodev-command-line

That addition becomes both introspectible (since query-qemu-features
options are introspectible regardless of their runtime state) and
queryable (not that this feature needs runtime queries, but others might).

And, since we're already proposing query-qemu-features for 4.0 for
another reason, making it 2 reasons instead of 1 feels like extra
justification for getting it done in a timely manner.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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