[libvirt] [PATCH 4/9] Public API Implementation

Jim Fehlig jfehlig at novell.com
Mon Jan 25 23:22:12 UTC 2010

Daniel P. Berrange wrote:
>>>> This looks safe, but there's a subtle problem with changing the existing
>>>> virDomainAttachDevice() entry point to call virDomainAttachDeviceFlags().
>>>> It will break compatability with old libvirtd, even though the old
>>>> libvirtd supports the virDomainAttachDevice() code.
>> Ah, yes - good catch.  Thanks.
>>>>  So we need to keep
>>>> the distinct paths in the public API & driver definitions. The eventual
>>>> low level hypervisor drivers can of course just turn their existing
>>>> impl into a thin wrapper to the new method..
>>> There's one other option actually - we could put compatability code in
>>> the remote driver client instead. Either, make it always invoke the old
>>> RPC call if flags == VIR_DOMAIN_DEVICE_MODIFY_LIVE, or have it invoke
>>> the new RPC call & fallback to the old RPC call if it gets an error
>>> indicating the new one doesn't exist.
>> Do you prefer the latter option?  After a quick look, I didn't spot any
>> existing compatibility code in the remote driver client.  The first
>> option might be slightly better wrt maintenance.
> Yes, the first option is certainly simpler / clearer code todo, so lets
> just do that first. We can easily revisit adding compat code in the
> remote driver client at a later date if we find it to be neccessary.

Revised patch below.


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