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    SubjectRe: [patch 2/8] [Intel IOMMU] Some generic search functions required to lookup device relationships.
    On Tue, Apr 10, 2007 at 04:11:38PM +0800, Shaohua Li wrote:
    > On Mon, 2007-04-09 at 20:46 -0700, Greg KH wrote:
    > > On Mon, Apr 09, 2007 at 02:55:54PM -0700, Ashok Raj wrote:
    > > > +/*
    > > > + * find the upstream PCIE-to-PCI bridge of a PCI device
    > > > + * if the device is PCIE, return NULL
    > > > + * if the device isn't connected to a PCIE bridge (that is its parent is a
    > > > + * legacy PCI bridge and the bridge is directly connected to bus 0), return its
    > > > + * parent
    > > > + */
    > > > +struct pci_dev *
    > > > +pci_find_upstream_pcie_bridge(struct pci_dev *pdev)
    > > > +{
    > > > + struct pci_dev *tmp = NULL;
    > > > +
    > > > + if (pdev->is_pcie)
    > > > + return NULL;
    > > > + while (1) {
    > > > + if (!pdev->bus->self)
    > > > + break;
    > > > + pdev = pdev->bus->self;
    > > > + /* a p2p bridge */
    > > > + if (!pdev->is_pcie) {
    > > > + tmp = pdev;
    > > > + continue;
    > > > + }
    > > > + /* PCI device should connect to a PCIE bridge */
    > > > + BUG_ON(pdev->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE);
    > > > + return pdev;
    > > > + }
    > > > +
    > > > + return tmp;
    > > > +}
    > >
    > > No locking while you walk up the bus list?
    > hmm, iommu driver didn't support pci hotplug in current stage. But we
    > can add lock here.

    Please do, as PCI-E hotplug is much more common than PCI hotplug these
    days (think ExpressCard in millions of laptops...)

    > > > --- linux-2.6.21-rc5.orig/include/linux/pci.h 2007-04-03 04:30:51.000000000 -0700
    > > > +++ linux-2.6.21-rc5/include/linux/pci.h 2007-04-03 06:58:58.000000000 -0700
    > > > @@ -126,6 +126,7 @@
    > > > unsigned short subsystem_device;
    > > > unsigned int class; /* 3 bytes: (base,sub,prog-if) */
    > > > u8 hdr_type; /* PCI header type (`multi' flag masked out) */
    > > > + u8 pcie_type; /* PCI-E device/port type */
    > > > u8 rom_base_reg; /* which config register controls the ROM */
    > > > u8 pin; /* which interrupt pin this device uses */
    > > >
    > > > @@ -168,6 +169,7 @@
    > > > unsigned int msi_enabled:1;
    > > > unsigned int msix_enabled:1;
    > > > unsigned int is_managed:1;
    > > > + unsigned int is_pcie:1;
    > >
    > > Do you really need both fields? Wouldn't just the pcie_type one work
    > > (with some NOT_PCIE type being set for it if it isn't I suppose.)
    > There are some encodings are reserved for future. Just don't want to use
    > reserved bits, as we don't know which one is proper for NOT_PCIE.

    What are the current encodings? I don't have my copy of the pci spec
    availble at the moment...

    thanks,

    greg k-h
    -
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