[virt-tools-list] Re: libosinfo - another try

[Arjun Roy]

On 10/22/2009 11:51 AM, Daniel P. Berrange wrote:
> Version number comparisons are a really bad way to determine whether
> functionality is available. RHEL-5 has 2.6.18 kernel, but has VirtIO
> support which didn't appear until 2.6.20-something. 
>
> If we need to determine if a particular item is available, we should
> have an explicit piece for metadata for it. eg to determine if virtio
> block is supported we should be checking a 'supported block devices'
> tag of some kind, rather comparing version numbers. Version numbers 
> should be purely informative, not used for any functional purpose
>
An example Cole gave me was the following:

Suppose we have a distro that can use two drivers for sound. If we have a KVM
hypervisor of version 1.2 and one of version 3.4, then the driver that must be
used is different.

More specifically, we want to be able to say that for KVM versions < 2.1, we use
ac97 and for versions 2.2 and up, we use intel_hda. And let's suppose the XML is
expressing that.

So in that case, how do we handle it?

-Arjun