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

[Peter Maydell]

On 20 December 2015 at 05:43, Peter Crosthwaite
<address@hidden> 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 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 <address@hidden>
> ---
> 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) {

This looks OK to me (and I like the effective API you get for
devices using things), but I don't know enough QOM/qdev internals
to be completely confident giving it a reviewed-by.

thanks
-- PMM