Re: [Qemu-devel] [for 1.5? Qemu-devel] [PATCH 2/3] chardev: Make the name of ringbuf device consistent

[Eric Blake]

On 05/20/2013 04:59 AM, Paolo Bonzini wrote:
> Il 20/05/2013 12:43, Paolo Bonzini ha scritto:
>> Il 20/05/2013 08:51, Lei Li ha scritto:
>>> Now we have ringbuf char device, but the backend name of it
>>> is a little confusion. We actually register it by 'memory', but
>>> the description in qemu-option, the name of open functions
>>> and the new api backend called it 'ringbuf'. It should keep
>>> consistent. This patch named it all to 'ringbuf'.
>>>
>>> Signed-off-by: Lei Li <address@hidden>
>>> ---
>>>  qapi-schema.json |    2 +-
>>>  qemu-char.c      |   12 ++++++------
>>>  2 files changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/qapi-schema.json b/qapi-schema.json
>>> index 9302e7d..61f6b34 100644
>>> --- a/qapi-schema.json
>>> +++ b/qapi-schema.json
>>> @@ -3321,7 +3321,7 @@
>>>                                         'spicevmc' : 'ChardevSpiceChannel',
>>>                                         'spiceport' : 'ChardevSpicePort',
>>>                                         'vc'     : 'ChardevVC',
>>> -                                       'memory' : 'ChardevRingbuf' } }
>>> +                                       'ringbuf': 'ChardevRingbuf' } }

This would be an ABI-visible change.

> Oh, actually this is different.  The only inconsistency is in the name
> of the type, the enum is consistent with the -chardev option and it
> cannot be renamed because it was in QEMU 1.4.
> 
> So we can change the type, but we can do that post 1.5.

Careful.  While the union existed in 1.4, it had fewer elements; the
'memory' element was added in commit 1da48c65, which means it has never
been released yet.  If you want to avoid an ABI change, then this commit
must go in NOW.

This also reiterates the question of how libvirt can know which members
of a union are present, since we have added members to the union that
were not available in 1.4 but still don't have a way to introspect which
chardevs can be added.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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