Re: [libvirt] [PATCH 0/8] Normalization API

On 09/18/2013 11:43 AM, Daniel P. Berrange wrote: > On Wed, Sep 18, 2013 at 09:38:23AM -0600, Eric Blake wrote: >> On 09/18/2013 09:32 AM, Cole Robinson wrote: >>> >>> Seems overkill IMO. Do we really need to add an API to facilitate the crappy >>> interface that is virsh detach-device? Will any other application ever want to >>> use this API? >> >> Yes, I can envision other use cases. In fact, virt-manager is one of them: >> >> Oftentimes, we add features to XML, but you don't have an easy way to >> probe if the feature is supported. Rather than complicate the (already >> large) capabilities xml to call out yet more features, it is rather >> simple to write up XML that tries to use the feature, then run it >> through the normalizing API, then look at the result. If the feature is >> still present in the output, then libvirt understands the feature (and >> you can safely use it); if the feature got stripped as unrecognized, >> then you can issue a much nicer error message to the user stating that >> the libvirtd on the other end of the connection can't honor the user's >> request. > > IMHO a better way to deal with that usage scenario is to add ability > to validate XML via the RNG schema to the API. > > eg we should add a "validate" flag that can be passed to virDomainDefineXML > / virDomainCreateXML that would enable RNG validation during parsing of > those APis. And possibly even have a dedicated API to request validation > of an XML doc in general (virt-xml-validate, but part of the API instead > of local CLI tool) > Yeah that could be useful. Though so would an API to just return the libvirt domain rng and let apps cache it, or parse it and use that as a poor man's XML capabilities and make virt-install --disk cache=? list all available cache modes without having to hardcode them. Granted that won't be accurate across hypervisors but its a start.