Re: [Qemu-devel] [PATCH 5/6] PPC: e500: Support dynamically spawned sysbus devices

[Scott Wood]

On Wed, 2014-07-02 at 19:12 +0200, Alexander Graf wrote:
> On 02.07.14 00:50, Scott Wood wrote:
> > Plus, let's please not hardcode any more addresses that are going to be
> > a problem for giving guests a large amount of RAM (yes, CCSRBAR is also
> > blocking that, but that has a TODO to parameterize).  How about
> > 0xf00000000ULL?  Unless of course we're emulating an e500v1, which
> > doesn't support 36-bit physical addressing.  Parameterization would help
> > there as well.
> 
> I don't think we have to worry about e500v1. I'll change it :).

We theoretically support it elsewhere...  Once parameterized, it
shouldn't be hard to base the address for this, CCSRBAR, and similar
things on whether MAS7 is supported.

> >> @@ -122,6 +131,77 @@ static void dt_serial_create(void *fdt, unsigned long 
> >> long offset,
> >>       }
> >>   }
> >>   
> >> +typedef struct PlatformDevtreeData {
> >> +    void *fdt;
> >> +    const char *mpic;
> >> +    int irq_start;
> >> +    const char *node;
> >> +    int id;
> >> +} PlatformDevtreeData;
> > What is id?  How does irq_start work?
> 
> "id" is just a linear counter over all devices in the platform bus so 
> that if you need to have a unique identifier, you can have one.
> 
> "irq_start" is the offset of the first mpic irq that's connected to the 
> platform bus.

OK, but why is that here but no irq_end, and no address range?  How do
allocations from the irq range happen?

> >> +static int sysbus_device_create_devtree(Object *obj, void *opaque)
> >> +{
> >> +    PlatformDevtreeData *data = opaque;
> >> +    Object *dev;
> >> +    SysBusDevice *sbdev;
> >> +    bool matched = false;
> >> +
> >> +    dev = object_dynamic_cast(obj, TYPE_SYS_BUS_DEVICE);
> >> +    sbdev = (SysBusDevice *)dev;
> >> +
> >> +    if (!sbdev) {
> >> +        /* Container, traverse it for children */
> >> +        return object_child_foreach(obj, sysbus_device_create_devtree, 
> >> data);
> >> +    }
> >> +
> >> +    if (matched) {
> >> +        data->id++;
> >> +    } else {
> >> +        error_report("Device %s is not supported by this machine yet.",
> >> +                     qdev_fw_name(DEVICE(dev)));
> >> +        exit(1);
> >> +    }
> >> +
> >> +    return 0;
> >> +}
> > It's not clear to me how this function is creating a device tree node.
> 
> It's not yet - it's only the stub that allows to plug in specific device 
> code that then generates device tree nodes :).

How does the plugging in work?

It looks like all this does is increment id.

-Scott