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

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Date:	Wed, 20 Feb 2013 18:19:27 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	shuah.khan@...com, dhowells@...hat.com
Cc:	Joerg Roedel <joro@...tes.org>, paulmck@...ux.vnet.ibm.com,
	linasvepstas@...il.com, davej@...hat.com, tglx@...utronix.de,
	mtk.manpages@...il.com, iommu@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
	shemminger@...tta.com, jiang.liu@...wei.com, wangyijing@...wei.com,
	shuahkhan@...il.com
Subject: Re: [PATCH 1/4] pci: Add PCI_BUS() and PCI_DEVID() interfaces to
 return bus number and device id

On Mon, Feb 11, 2013 at 4:00 PM, Shuah Khan <shuah.khan@...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@...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
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