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). > 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. Kevin
