Re: [PATCH 1/4] pci: Add PCI_BUS() and PCI_DEVID() interfaces to return bus number and device id

Bjorn Helgaas
2013-02-21T01:19:50Z

On Mon, Feb 11, 2013 at 4:00 PM, Shuah Khan <shuah.khan@hp.com> wrote:
> pci defines PCI_DEVFN(), PCI_SLOT(), and PCI_FUNC() interfaces, however,
> it doesn't have interfaces to return PCI bus and PCI device id. Drivers
> (AMD IOMMU, and AER) implement module specific definitions for PCI_BUS()
> and AMD_IOMMU driver also has a module specific interface to calculate PCI
> device id from bus number and devfn.
>
> Add PCI_BUS and PCI_DEVID interfaces to return PCI bus number and PCI device
> id respectively to avoid the need for duplicate definitions in other modules.
> AER driver code and AMD IOMMU driver define PCI_BUS. AMD IOMMU driver defines
> an interface to calculate device id from bus number, and devfn pair.
>
> Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> ---
> include/uapi/linux/pci.h | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/include/uapi/linux/pci.h b/include/uapi/linux/pci.h
> index 3c292bc0..6b2c8b3 100644
> --- a/include/uapi/linux/pci.h
> +++ b/include/uapi/linux/pci.h
> @@ -30,6 +30,10 @@
> #define PCI_DEVFN(slot, func) ((((slot) & 0x1f) << 3) | ((func) & 0x07))
> #define PCI_SLOT(devfn) (((devfn) >> 3) & 0x1f)
> #define PCI_FUNC(devfn) ((devfn) & 0x07)
> +#define PCI_DEVID(bus, devfn) ((((u16)bus) << 8) | devfn)
> +
> +/* return bus from PCI devid = ((u16)bus_number) << 8) | devfn */
> +#define PCI_BUS(x) (((x) >> 8) & 0xff)
>
> /* Ioctls for /proc/bus/pci/X/Y nodes. */
> #define PCIIOC_BASE ('P' << 24 | 'C' << 16 | 'I' << 8)

David, can you point me at a description of include/uapi ... what is
there and why, and how we should decide what new things go in
include/uapi/linux/pci.h as opposed to include/linux/pci.h? Maybe
there should be something in Documentation/?

I'm guessing it's something to do with being exported to userland, but
I'm not sure the things in this patch (PCI_DEV_ID, PCI_BUS) are really
exportable in the sense of being used for syscalls, etc.

Bjorn