Re: [PATCH v5 13/18] pci: introduce pci_find_the_only_child()

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Feb 16, 2023 at 09:03:51PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> To be used in further patch to identify the device hot-plugged into
> pcie-root-port.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Reviewed-by: Anton Kuchin <antonkuchin@yandex-team.ru>

Wait a second does this work for multifunction devices correctly?

> ---
>  include/hw/pci/pci.h |  1 +
>  hw/pci/pci.c         | 33 +++++++++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index d5a40cd058..b6c9c44527 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -341,6 +341,7 @@ void pci_for_each_device_under_bus_reverse(PCIBus *bus,
>  void pci_for_each_bus_depth_first(PCIBus *bus, pci_bus_ret_fn begin,
>                                    pci_bus_fn end, void *parent_state);
>  PCIDevice *pci_get_function_0(PCIDevice *pci_dev);
> +PCIDevice *pci_find_the_only_child(PCIBus *bus, int bus_num, Error **errp);
>  
>  /* Use this wrapper when specific scan order is not required. */
>  static inline
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 208c16f450..34fd1fb5b8 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1771,6 +1771,39 @@ void pci_for_each_device(PCIBus *bus, int bus_num,
>      }
>  }
>  
> +typedef struct TheOnlyChild {
> +    PCIDevice *dev;
> +    int count;
> +} TheOnlyChild;
> +
> +static void the_only_child_fn(PCIBus *bus, PCIDevice *dev, void *opaque)
> +{
> +    TheOnlyChild *s = opaque;
> +
> +    s->dev = dev;
> +    s->count++;
> +}
> +
> +PCIDevice *pci_find_the_only_child(PCIBus *bus, int bus_num, Error **errp)
> +{
> +    TheOnlyChild res = {0};
> +
> +    pci_for_each_device(bus, bus_num, the_only_child_fn, &res);
> +
> +    if (!res.dev) {
> +        assert(res.count == 0);
> +        error_setg(errp, "No child devices found");
> +        return NULL;
> +    }
> +
> +    if (res.count > 1) {
> +        error_setg(errp, "Several child devices found");
> +        return NULL;
> +    }
> +
> +    return res.dev;
> +}
> +
>  const pci_class_desc *get_class_desc(int class)
>  {
>      const pci_class_desc *desc;
> -- 
> 2.34.1