Re: [Qemu-devel] [PATCH v2 1/2] console: add hw_screen_dump_async

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/05/2012 11:29 AM, Avi Kivity wrote:
> On 03/05/2012 07:27 PM, Anthony Liguori wrote:
>> On 03/05/2012 11:20 AM, Avi Kivity wrote:
>>> On 03/05/2012 04:33 PM, Anthony Liguori wrote:
>>>>
>>>>
>>>> async in QEMU doesn't mean "generate a QMP event when you're done".
>>>> It should mean execute this closure when you finish (function pointer
>>>> + opaque).
>>>>
>>>> The QMP event should be dispatched from the closure such that the
>>>> screendump code doesn't have to have a direct dependency on QMP.
>>>>
>>>
>>> What about using the parallel execution facility of qmp?  It's silly to
>>> duplicate every command X with X-async and X-COMPLETED.
>>
>> We need to switch over to QAPI to get there.
>
> Just an implementation detail, yes?  No spec/protocol changes?

Correct.

>
>>    We're pretty close to being there.  Luiz, about how long do you
>> think before we get there?
>
> It's a pity to add new commands along the way.

It's more complicated than this unfortunately.

A client needs to be able to determine whether the 'screendump' command works as 
expected.  Unfortunately, when QXL was introduced, 'screendump' became broken 
across multiple releases.

screendump is the right interface, but since it was broken in multiple releases, 
we need another command for a client to determine that it's not broken.  In the 
short term, screendump_async is that.  After QAPI, it will probably be a 
screendump2.

I don't mind introducing short term commands and then deprecating it 
particularly when they are marked as such.

Regards,

Anthony Liguori