Re: [Qemu-devel] [PATCH v13 6/6] qom: support arbitrary non-scalar properties with -object

[Daniel P. Berrange]

On Mon, Sep 19, 2016 at 12:58:30PM +0100, Daniel P. Berrange wrote:
> The current -object command line syntax only allows for
> creation of objects with scalar properties, or a list
> with a fixed scalar element type. Objects which have
> properties that are represented as structs in the QAPI
> schema cannot be created using -object.
> 
> This is a design limitation of the way the OptsVisitor
> is written. It simply iterates over the QemuOpts values
> as a flat list. The support for lists is enabled by
> allowing the same key to be repeated in the opts string.
> 
> It is not practical to extend the OptsVisitor to support
> more complex data structures while also maintaining
> the existing list handling behaviour that is relied upon
> by other areas of QEMU.
> 
> Fortunately there is no existing object that implements
> the UserCreatable interface that relies on the list
> handling behaviour, so it is possible to swap out the
> OptsVisitor for a different visitor implementation, so
> -object supports non-scalar properties, thus leaving
> other users of OptsVisitor unaffected.

Urgh, I've just discovered that this is not in fact true.

The 'memory-backend' object type uses uint16List which
has the hacky list syntax

  -object memory-backend-ram,\
          id=ram-node2,size=24578621440,policy=bind,\
          host-nodes=1-2,host-nodes=5,host-nodes=7,

So I'll need to figure out a way to preserve this syntax...

Regards,
Daniel
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