On Mon, 2015-03-30 at 12:55 +0200, Lucas Stach wrote:
> This adds a simple way to get the root port a given device
> is connected to.
>
> Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> ---
> v2: new patch in v2
> v3: rename to pci_find_rootport to fit better with other API
> v4: - rename to make it obvious that this function is PCIe specific
> - fixes wrong assumption about what is a root bus in the presence
> virtual buses
> ---
> drivers/pci/search.c | 20 ++++++++++++++++++++
> include/linux/pci.h | 1 +
> 2 files changed, 21 insertions(+)
>
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index a20ce7d5e2a7..d7c599103ae1 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -384,3 +384,23 @@ int pci_dev_present(const struct pci_device_id *ids)
> return 0;
> }
> EXPORT_SYMBOL(pci_dev_present);
> +
> +/**
> + * pcie_find_root_port - Returns the root port the given device is connected to.
> + * @dev: PCI device for which the root port should be found.
> + */
> +struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> +{
> + struct pci_bus *bus = dev->bus;
> +
> + /* if this device is located on the root bus, it is a root port */
> + if (pci_is_root_bus(bus))
> + return dev;
It could also be a root complex endpoint or a conventional PCI
device/bridge sitting on the host bridge bus.
> +
> + /* walk up the PCI hierarchy to the first level below the root */
> + while (bus->parent && bus->parent->parent)
> + bus = bus->parent;
> +
> + return bus->self;
> +}
> +EXPORT_SYMBOL(pcie_find_root_port);
IMHO, this makes too many assumptions about the topology that it's
working with for a generic interface. Your usage may be fairly fixed,
but there are too many cases where it could return something that's not
a root port as a general interface. Thanks,
Alex
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 211e9da8a7d7..308c71081034 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -844,6 +844,7 @@ static inline struct pci_dev *pci_get_bus_and_slot(unsigned int bus,
> }
> struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from);
> int pci_dev_present(const struct pci_device_id *ids);
> +struct pci_dev *pcie_find_root_port(struct pci_dev *dev);
>
> int pci_bus_read_config_byte(struct pci_bus *bus, unsigned int devfn,
> int where, u8 *val);
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