Re: [Qemu-devel] [PATCH 05/27] qapi: add SIZE type parser to string_input_visitor

[Paolo Bonzini <pbonzini@redhat.com>]

Il 27/11/2013 18:02, Markus Armbruster ha scritto:
> I have to admit I can't tell offhand what the heck QMP's netdev_add
> accepts, because I don't understand what "'*props:': '**'" means in
> qapi-schema.json.  Even today, we permit code to serve as documentation
> and specification for new features.  I wish we didn't.

It is ignored, because qmp_netdev_add does not use an
automatically-generated unmarshaler.

> Anyway, whatever it parses ends up in a QDict, as usual.

The QDict comes straight from the monitor dispatch.  It is the QDict
that ordinarily would be unmarshaled by automatically-generated code.

> The part that sucks is the use of QemuOpts as netdev_add() parameter,
> 
> It made some sense when it was done, because then the command line was
> the only user, its data type for option parameters was (and is)
> QemuOpts, and QemuOpts was the least inconvenient way to do a function
> that wants a a discriminated union of parameters, like netdev_add does.
> 
> It stopped making sense when we started using it from QMP, whose data
> type for parameters is QDict.  I shoehorned netdev_add into QMP in its
> early days.  Hinsight 20/20...

Yes.

> In my opinion, use of QemuOpts for anything but parsing parameter
> strings has become a mistake.

Yes.  OTOH QemuOpts is the only reason why QMP and HMP can use a common
back-end (netdev_add).  With object-add you don't use QemuOpts (for good
reasons: you want to separate the human-oriented parsing and the
JSON-oriented parsing) and thus you need separate code for QMP and
HMP---at least for now.

The HMP code can use QemuOpts just like vl.c.  The QMP code would use
qdict_iter or qdict_first/next and call object_set_property for each
element of the dictionary.

> Laszlo converted net.c to saner internal interfaces (commit
> d195325..1a0c095).  Perhaps we can build on that.

Yeah, that could be an idea.  Another is to convert netdevs to QOM
(reusing Laszlo's data structures of course) and then just use
object-add and -object.

Paolo