Re: [Qemu-devel] [PATCH RFC 0/3] basic support for composing sysbus devices

[Anthony Liguori]

On 06/15/2011 01:56 PM, Blue Swirl wrote:
> On Tue, Jun 14, 2011 at 4:21 PM, Anthony Liguori<address@hidden>  wrote:
> > Which suggests that we really need to move away from declarative device
> > definitions.  It makes it hard to have variable numbers of properties.
>
> I'd suppose the number of slots could be fixed. Then the declaration could be
>        DEFINE_PROP_SOCKETS(I440FXState, slot, 32),

That's fine for something like a PCI controller, but for something like 
a multiport network card, it's really desirable to be able to specify 
the number of ports as part of the config.  IOW:

 -device virtio-net-pci,ports=8,netdev[0]=tap0,netdev[1]=tap1,...

> > In this case, piix3 would be defined as:
> >
> > struct I440FXState {
> >     PIIX3 piix3;
> >     PCIDevice slots[32];
> > };
> >
> > Which suggests we need an initfn to do the following:
> >
> > void i440fx_initfn(...) {
> >    qdev_init_inplace(&dev->piix3, "PIIX3");
> >    dev->slot[1] =&dev->piix3->bus;
> > }
> >
> > This gets hard to do well in C though.  I'm not sure how we could make
> > DEFINE_PROP_PLUG/SOCKET type safe.
>
> DEFINE_PROP_PCI_SOCKET()?

Yeah, that's why I said, "hard to do well".  It makes it very hard to 
add new socket types.

Regards,

Anthony Liguori

>