Re: [Qemu-devel] [PATCH v6 1/6] qdev: get_child_bus(): Use QOM lookup if available

[Alistair Francis <alistair.francis@xilinx.com>]

On Wed, Jan 6, 2016 at 4:25 PM, Peter Crosthwaite
<crosthwaitepeter@gmail.com> wrote:
> On Wed, Jan 6, 2016 at 4:18 PM, Alistair Francis
> <alistair.francis@xilinx.com> wrote:
>> On Sat, Dec 19, 2015 at 9:43 PM, Peter Crosthwaite
>> <crosthwaitepeter@gmail.com> wrote:
>>> qbus_realize() adds busses as a QOM child of the device in addition to
>>> adding it to the qdev bus list. Change get_child_bus() to use the QOM
>>> child if it is available. This takes priority over the bus-list, but
>>> the child object is checked for type correctness.
>>
>> This doesn't cause problems for anything else? Is there anything else
>> with the same name or something where this causes conflicts?
>>
>
> Not that I know of, I'm just being defensive as it is core code. I
> suspect that that ignored failure path on the child setter is
> incorrect but I can't prove it beyond all doubt.

I just re-read what I said and it doesn't really make sense. My only
concern was busses with the same name somehow having conflicts that
weren't previously there. I can't think of any case where this would
happen though.

Acked-by: Alistair Francis <alistair.francis@xilinx.com>

Thanks,

Alistair

>
> Regards,
> Peter
>
>> Thanks,
>>
>> Alistair
>>
>>>
>>> This prepares support for aliasing of buses. The use case is SoCs,
>>> where a SoC container needs to present buses to the board level, but
>>> the buses are implemented by controller IP we already model as self
>>> contained qbus-containing devices.
>>>
>>> Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
>>> ---
>>> Currently qbus_realize() ignores errors from object_property_add_child,
>>> so it is hard to guarantee that the QOM linkage is reliable. If it were
>>> the case that that object_property_add_child was supposed to be error
>>> asserting, we could remove the old bus-list strcmp iterator altogether.
>>>
>>>  hw/core/qdev.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
>>> index b3ad467..c96c464 100644
>>> --- a/hw/core/qdev.c
>>> +++ b/hw/core/qdev.c
>>> @@ -581,6 +581,12 @@ void qdev_pass_gpios(DeviceState *dev, DeviceState *container,
>>>  BusState *qdev_get_child_bus(DeviceState *dev, const char *name)
>>>  {
>>>      BusState *bus;
>>> +    Object *child = object_resolve_path_component(OBJECT(dev), name);
>>> +
>>> +    bus = (BusState *)object_dynamic_cast(child, TYPE_BUS);
>>> +    if (bus) {
>>> +        return bus;
>>> +    }
>>>
>>>      QLIST_FOREACH(bus, &dev->child_bus, sibling) {
>>>          if (strcmp(name, bus->name) == 0) {
>>> --
>>> 1.9.1
>>>
>>>
>