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

[Eric Blake]

On 3/28/19 3:06 PM, Eric Blake wrote:
> 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.
>>>

> 
> 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.

And answering myself after a bit more thought - the question is not just
about "can we use the command line instead of envvars", but one step
further of "once we are using the command line, what works in this
release as opposed to added in later releases".  So we still want
introspection to land on the full QAPI types for audiodev, even if, for
4.0, we can't actually use QMP to change them. This means we at least
need a QMP command that references the QAPI types (even if the command
is named "x-audiodev-dummy" and always fails), so that the types at
least make it into the introspection output, coupled with the
query-qemu-features bit to state that even when we remove the hack of
the x-audiodev-dummy command later, we can still use audiodev and scrape
enough out of introspection for our needs.

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

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