[Libvir] [RFC] Host and guest capabilities

Daniel Veillard veillard at redhat.com
Wed Mar 7 15:17:51 UTC 2007

On Wed, Mar 07, 2007 at 02:56:47PM +0000, Richard W.M. Jones wrote:
> Daniel Veillard wrote:
> >  This sounds too variable, adding an entry point per capability of
> >some of the hypervisor available will lead to just too many entry points
> >once the set of virtualization engines and associated benefits increase.
> >That's one of the places where I feel wy more comfortable returning an
> >XML description which can then be augmented as more features are added.
> But this API is _precisely_ designed to be extensible.  The 
> virCapabilities structure is not accessible to callers (unlike, say, 
> virNodeInfo), except through accessor functions.  We can add accessor 
> functions in future.
> Returning XML just punts the problem elsewhere.  Now clients need to 
> worry about parsing the XML, and there's no real guarantee that the XML 
> won't change in a way which is incompatible with the clients.  Whereas 
> by using ordinary functions we have that guarantee.

  It's easier to make that garantee at the XML level in my opinion.
And adding pile of accessor functions for a struct that you don't feel
you can define well enough to export is not the way I like to define APIs.
Sorry, we disagree.


Red Hat Virtualization group http://redhat.com/virtualization/
Daniel Veillard      | virtualization library  http://libvirt.org/
veillard at redhat.com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine  http://rpmfind.net/

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