On Thu, Oct 06, 2016 at 05:30:05PM +0200, Kevin Wolf wrote: > Am 06.10.2016 um 17:18 hat Daniel P. Berrange geschrieben: > > On Thu, Oct 06, 2016 at 05:10:42PM +0200, Kevin Wolf wrote: > > > Am 30.09.2016 um 16:45 hat Daniel P. Berrange geschrieben: > > > > Some of the historical command line opts that had their > > > > keys in in a completely flat namespace are now represented > > > > by QAPI schemas that use a nested structs. When converting > > > > the QemuOpts to QObject, there is no information about > > > > compound types available, so the QObject will be completely > > > > flat, even after the qdict_crumple() call. So when starting > > > > a struct, we may not have a QDict available in the input > > > > data, so we auto-create a QDict containing all the currently > > > > unvisited input data keys. Not all historical command line > > > > opts require this, so the behaviour is opt-in, by specifying > > > > how many levels of structs are permitted to be auto-created. > > > > > > > > Note that this only works if the child struct is the last > > > > field to the visited in the parent struct. This is always > > > > the case for currently existing legacy command line options. > > > > > > > > The example is the NetLegacy type which has 3 levels of > > > > structs. The modern way to represent this in QemuOpts would > > > > be the dot-separated component approach > > > > > > > > -net vlan=1,id=foo,name=bar,opts.type=tap,\ > > > > opts.data.fd=3,opts.data.script=ifup > > > > > > > > The legacy syntax will just be presenting > > > > > > > > -net vlan=1,id=foo,name=bar,type=tap,fd=3,script=ifup > > > > > > > > So we need to auto-create 3 levels of struct when visiting. > > > > > > > > The implementation here will enable visiting in both the > > > > modern and legacy syntax, compared to OptsVisitor which > > > > only allows the legacy syntax. > > > > > > So you're actually introducing the modern syntax only now? > > > > No, the modern syntax is fully implemented by patch 8. > > "now" in the sense of "in this series" (because this means that there is > no external API to preserve yet).
Well the syntax implemented in patch 8 is designed to 100% mirror the QAPI schema structure nesting. I don't think we want to change that behaviour. If there are certain QAPI schemas structs can still have freedom to change though, its fine to reconsider them > > > This patch is about adding hacks for the legacy syntax used > > by the OptsVisitor. The OptsVisitor didn't interpret struct > > nesting at all, so everything looked flat - this only works > > as long as you don't have the same key used in multiple > > structs at different levels, so is not useful as a general > > approach - it only works by luck really. > > > > > I don't think an "opts.data." prefix makes a lot of sense. I suspect the > > > schema looks this way only because we didn't have flat unions in 1.2. > > > > > > So, considering that it is a purely internally used type not visible in > > > QMP, would it make sense to change NetLegacy to be a flat union instead, > > > with NetLegacyOptions as the common base? Then you get the same flat > > > namespace that we always had and that makes much more sense as an API. > > > > Changing that will impact on the QMP data structure, so I don't think > > we can do that. > > I don't see this type used in QMP at all. It's only used for command > line parsing, and only with the OptsVisitor, so I think we're fine if we > flatten it now. Ok, yes, it seems "NetLegacy" is only used in CLI arg parsing, so we do have some freedom there. This patch was also needed for -numa handling too - again we might have some flexibility to flatten that. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|
