From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g1t0027.austin.hp.com ([15.216.28.34]:25226 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751069Ab3BYQhc (ORCPT ); Mon, 25 Feb 2013 11:37:32 -0500 Message-ID: <1361810245.2975.14.camel@lorien2> Subject: Re: [PATCH 1/4] pci: Add PCI_BUS() and PCI_DEVID() interfaces to return bus number and device id From: Shuah Khan Reply-To: shuah.khan@hp.com To: Bjorn Helgaas Cc: dhowells@redhat.com, Joerg Roedel , paulmck@linux.vnet.ibm.com, linasvepstas@gmail.com, davej@redhat.com, tglx@linutronix.de, mtk.manpages@gmail.com, iommu@lists.linux-foundation.org, LKML , linux-pci@vger.kernel.org, shemminger@vyatta.com, jiang.liu@huawei.com, wangyijing@huawei.com, shuahkhan@gmail.com Date: Mon, 25 Feb 2013 09:37:25 -0700 In-Reply-To: References: <1360623637.2950.63.camel@lorien2> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, 2013-02-20 at 18:19 -0700, Bjorn Helgaas wrote: > On Mon, Feb 11, 2013 at 4:00 PM, Shuah Khan 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 > > --- > > 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,David, Looks like the following thread answers some of the questions about when this uapi export was done on the existing defines. https://lkml.org/lkml/2011/7/28/198 Sounds like the concern is that the older defines PCI_DEVFN, PCI_SLOT, PCI_FUNC, and PCI_DEVID could be exported, but not the new ones I added. I could find any discussion on whether these four older defines are exportable or the reasons for the export in the above thread. So the question is if uapi/linux.pci.h isn't the right place, do you have a recommendation on where they belong. The only alternative I can think of is include/linux/pci.h. It makes functional and logical sense to add the new defines to where the existing ones are defines. At least, not knowing the details of the change that moved PCI_DEVFN etc. to uapi/pci.h, that is my conclusion. -- Shuah