On Tue, May 10, 2016 at 07:15:01PM -0400, Cole Robinson wrote: > On 05/10/2016 11:50 AM, Daniel P. Berrange wrote: > > On Tue, May 10, 2016 at 11:26:29AM -0400, Cole Robinson wrote: > >> On 05/10/2016 05:10 AM, Daniel P. Berrange wrote: > >>> On Mon, May 09, 2016 at 06:53:01PM -0400, Cole Robinson wrote: > >>>> On 05/09/2016 09:48 AM, Daniel P. Berrange wrote: > >>> > >>> IMHO it is a total failure if we require the application to extend its > >>> parser every time we add a new enum to the domain capabilities. We have > >>> the ability to design something that is data driven - we should not build > >>> something it is forced to be code driven with code changes for every > >>> libvirt addition. > >> > >> This is ignoring the point I made previously that the schema is not already > >> fully introspectable. Most of the current enums cannot be programmatically > >> consumed anyways, because there's no way to map an enum name to its domain > >> XML > >> property. So if that's our goal to be data driven, we should address that > >> issue first. > > > > Knowing the mapping of the capabilities enums to the domain schema is > > a pre-requisite for consuming the capabilities data, no matter which > > approach discussed in this thread is chosen. Assuming the app knows > > that mapping, then the enum conditionals can be programmatically > > handled with the approach I describe. > > > > Providing a way for the app to automatically determine the mapping > > from capabilities enums to the domain schema would be a nice > > addition, but it isn't a pre-requisite blocker for what's discussed > > here. It is something that can be deal with in parallel. > > > >> I can't really think of a good way to represent that without nesting > >> deeply or using specially formatted strings. Do you have a suggestion > >> for that? > > > > Probably the best thing is to use a very simplified xpath style notation. > > If we add a 'mapping' attribute to the <enum> that expresses the attribute > > or element it is associated with, relative to the parent container element. > > > > eg, consider the tests/domaincapsschemadata/domaincaps-qemu_1.6.50-1.xml > > data file with the mapping info: > > > > <domainCapabilities> > > <path>/usr/bin/qemu-system-x86_64</path> > > <domain>kvm</domain> > > <machine>pc-1.2</machine> > > <arch>x86_64</arch> > > <os supported='yes'> > > <loader supported='yes'> > > <value>/usr/share/AAVMF/AAVMF_CODE.fd</value> > > <value>/usr/share/OVMF/OVMF_CODE.fd</value> > > <enum name='type' mapping="@type"> > > <value>rom</value> > > <value>pflash</value> > > </enum> > > <enum name='readonly' mapping="@readonly"> > > <value>yes</value> > > <value>no</value> > > </enum> > > </loader> > > </os> > > <devices> > > <disk supported='yes'> > > <enum name='diskDevice' mapping="@device"> > > <value>disk</value> > > <value>cdrom</value> > > <value>floppy</value> > > <value>lun</value> > > </enum> > > <enum name='bus' mapping="target/@bus"> > > <value>ide</value> > > <value>fdc</value> > > <value>scsi</value> > > <value>virtio</value> > > <value>usb</value> > > </enum> > > </disk> > > <hostdev supported='yes'> > > <enum name='mode' mapping="@mode"> > > <value>subsystem</value> > > </enum> > > <enum name='startupPolicy' mapping="source/@startupPolicy"> > > <value>default</value> > > <value>mandatory</value> > > <value>requisite</value> > > <value>optional</value> > > </enum> > > <enum name='subsysType' mapping="@type"> > > <value>usb</value> > > <value>pci</value> > > <value>scsi</value> > > </enum> > > <enum name='capsType' mapping="@type"/> > > <enum name='pciBackend' mapping="driver/@name"> > > <value>default</value> > > <value>kvm</value> > > <value>vfio</value> > > </enum> > > </hostdev> > > </devices> > > <features> > > <gic supported='no'/> > > </features> > > </domainCapabilities> > > > > > > NB, with my proposed conditionals, the hostdev enums above would actually > > want to be different. eg it would want to look like this: > > > > <enum name='mode' mapping="@mode"> > > <value>subsystem</value> > > </enum> > > <enum name='startupPolicy' mapping="source/@startupPolicy"> > > <value>default</value> > > <value>mandatory</value> > > <value>requisite</value> > > <value>optional</value> > > </enum> > > <enum name='type' mapping="@type"> > > <condition> > > <enum name='mode' value='subsystem'/> > > </condition> > > <value>usb</value> > > <value>pci</value> > > <value>scsi</value> > > </enum> > > <enum name='driver' mapping="driver/@name"> > > <condition> > > <enum name='mode' value='subsystem'/> > > <enum name='type' value='pci'/> > > </condition> > > <value>default</value> > > <value>kvm</value> > > <value>vfio</value> > > </enum> > > > > Yeah that mapping= bit makes sense to me. > > I don't have time to see pick this up now though, so I've stuffed it in a bug:
Thinking about this some more last night, I realize that once we have the 'mapping' attribute, then the choice of values in the 'name' attribute becomes totally irrelevant. IOW, we could use your suggestion for giving each enum a unique name, eg 'spiceGL', 'vncGL', etc, etc. So apps which want to consume this data have a choice between just matching on explicit enum names and ignoring the <condition> rules, or they can match on the 'mapping' attribute and use the <condition> rules.. So we get the best of both ideas. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
