Re: [Qemu-devel] [PATCH] Add 'query-events' command to QMP to query async events

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 16 May 2012 11:18:22 -0500
Anthony Liguori <anthony@codemonkey.ws> wrote:

> On 05/16/2012 11:04 AM, Eric Blake wrote:
> > On 05/16/2012 06:55 AM, Daniel P. Berrange wrote:
> >> From: "Daniel P. Berrange"<berrange@redhat.com>
> >>
> >> Sometimes it is neccessary for an application to determine
> >> whether a particular QMP event is available, so they can
> >> decide whether to use compatibility code instead. This
> >> introduces a new 'query-events' command to QMP todo just
> >
> > s/todo/to do/
> >
> >> that
> >>
> >>   { "execute": "query-events" }
> >>   {"return": [{"name": "WAKEUP"},
> >>               {"name": "SUSPEND"},
> >>               {"name": "DEVICE_TRAY_MOVED"},
> >>               {"name": "BLOCK_JOB_CANCELLED"},
> >>               {"name": "BLOCK_JOB_COMPLETED"},
> >>               ...snip...
> >>               {"name": "SHUTDOWN"}]}
> >>
> >> * monitor.c: Split out MonitorEvent ->  string conversion
> >>    into monitor_protocol_event_name() API. Add impl of
> >>    qmp_query_events monitor command handler
> >> * qapi-schema.json, qmp-commands.hx: Define contract of
> >>    query-events command
> >
> > Definitely useful for libvirt.
> >
> >
> >> +static const char *monitor_protocol_event_name(MonitorEvent event)
> >> +{
> >>       switch (event) {
> >>           case QEVENT_SHUTDOWN:
> >> -            event_name = "SHUTDOWN";
> >> +            return "SHUTDOWN";
> >>               break;
> >
> > These 'break' statements are now unreachable; does this matter in qemu
> > coding style?
> 
> Seems like we should just take the opportunity to kill off the function entirely 
> and replace it with a table:
> 
> static const char *monitor_event_names[] = {
>   [QEVENT_SHUTDOWN] = "SHUTDOWN",
>   ...
> };

Yes, that's really better.

Btw, the ideal way of having this would be to add the event type to the
qapi and then add schema introspection.

As I'm not sure I can guarantee that for 1.2, I'm ok with this command.

Anthony, I'm assuming you're ok too.