[libvirt] [PATCH 11/15] qemu: capabilities: Detect support for gluster debug setting

[Eric Blake]

On 10/21/2016 08:22 AM, Peter Krempa wrote:

>>>  static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
>>> -    { "bogus/path/to/satisfy/compiler", 0 },
>>> +    { "blockdev-add/arg-type/options/+gluster/debug-level", QEMU_CAPS_GLUSTER_DEBUG_LEVEL},
>>
>> Okay, I see how you plan to use this.
>>
>> BIG WARNING FLAG - in qemu 2.7, blockdev-add is unstable (it should have
>> been named x-blockdev-add; but we goofed); but you can use the existence
>> of x-blockdev-del as a witness that blockdev-add is incomplete.
>>
>> In qemu 2.8, we are taking advantage of the fact that 2.7 wasn't
>> complete in order to get rid of the 'options' nesting layer; the plan is
>> to also rename x-blockdev-add at the same time.  Which means this probe,
>> as written, will only succeed for 2.7.
> 
> So. Should I add both? One with the "options" indirection and one
> without? Since there is no other way to access the structure than via
> blockdev-add and I really don't want to add a version check I see it as
> the only option.

Qemu 2.8 isn't released yet.  We tend to only commit into libvirt
support for released qemu. So I think I'm okay with using this patch
as-is (it will detect support for 2.7); then a followup patch once 2.8
is actually released and we've tested that we can still detect the
capability with the new-and-improved blockdev-add and corresponding
second query addition at that time.

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

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