Re: [Qemu-devel] [PATCH] Name the default PCI bus "pci.0" on all architectures

[Markus Armbruster]

Paul Brook <address@hidden> writes:

>> The system emulators for each arch are using inconsistent
>> naming for the default PCI bus "pci" vs "pci.0". Since it
>> is conceivable we'll have multiple PCI buses in the future
>> standardize on "pci.0" for all architectures. This ensures
>> mgmt apps can rely on a name when assigning PCI devices an
>> address on the bus using eg '-device e1000,bus=pci.0,addr=3'
>
> No. Bus names are local to the parent device.  None of the host bridges 
> support multiple bridges, so the ".0" suffix makes no sense.  The parent 
> device has no idea whether it owns the "default" pci bus or not.
> If you have multiple PCI busses then you can identify them by the device path.

>From qbus_create_inplace():

    if (name) {
        /* use supplied name */
        bus->name = qemu_strdup(name);
    } else if (parent && parent->id) {
        /* parent device has id -> use it for bus name */
        len = strlen(parent->id) + 16;
        buf = qemu_malloc(len);
        snprintf(buf, len, "%s.%d", parent->id, parent->num_child_bus);
        bus->name = buf;
    } else {
        /* no id -> use lowercase bus type for bus name */
        len = strlen(info->name) + 16;
        buf = qemu_malloc(len);
        len = snprintf(buf, len, "%s.%d", info->name,
                       parent ? parent->num_child_bus : 0);
        for (i = 0; i < len; i++)
            buf[i] = qemu_tolower(buf[i]);
        bus->name = buf;
    }

If appending ".0" really makes no sense when the device has just one
bus, then we shouldn't append it in cases 2 & 3.

But I'd simply append it always.  One bus is just as countable as many.