Re: [Qemu-devel] [PATCH 4/9] Add S390x virtio machine bus

[Alexander Graf]

On 19.10.2009, at 21:34, Gerd Hoffmann wrote:

> > +VirtIOS390Bus *s390_virtio_bus_init(ram_addr_t *ram_size)
> > +{
> > +    VirtIOS390Bus *bus;
> > +
> > +    bus = (VirtIOS390Bus *)qbus_create(&s390_virtio_bus_info,  
> > NULL, "s390-virtio");
>
> While a cast works the political correct way to do this is using  
> DO_UPCAST.

Oh - that one's new to me :-)

> Also I'd suggest to add a sysbus -> s390-virtio bus bridge device,  
> so your bus gets properly hooked up in the device tree.  Have a look  
> at the (quite simple) "isabus-bridge" device in isa-bus.c, which is  
> used with 'qemu -M isapc'.  You'll see the s390-virtio bus and all  
> virtio devices attached to it in 'info qtree' then.

Uh, ok :o. Is that really important?

> > +    bus = (VirtIOS390Bus *)dev->qdev.parent_bus;
>
> DO_UPCAST().
>
> > +VirtIOS390Device *s390_virtio_bus_console(VirtIOS390Bus *bus)
> > +{
> > +    return bus->console;
> > +}
>
> What this is needed for?

We need to know the console to do early printk. I figured it'd be  
better to have a function returning it, so we could possibly change  
semantics later.

Alex