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    Subject[PATCH v4 07/12] PCI: Introduce /sys/bus/pci/rescan
    Date
    This interface allows the user to force a rescan of all PCI buses
    in system, and rediscover devices that have been removed earlier.

    pci_bus_attrs implementation from Trent Piepho.

    Thanks to Vegard Nossum for discovering locking issues with the
    sysfs interface.

    Cc: Trent Piepho <xyzzy@speakeasy.org>
    Signed-off-by: Alex Chiang <achiang@hp.com>
    ---

    Documentation/ABI/testing/sysfs-bus-pci | 9 +++++++++
    drivers/pci/pci-driver.c | 1 +
    drivers/pci/pci-sysfs.c | 29 +++++++++++++++++++++++++++++
    drivers/pci/pci.h | 6 ++++++
    4 files changed, 45 insertions(+), 0 deletions(-)

    diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
    index e638e15..ea4aee2 100644
    --- a/Documentation/ABI/testing/sysfs-bus-pci
    +++ b/Documentation/ABI/testing/sysfs-bus-pci
    @@ -41,6 +41,15 @@ Description:
    for the device and attempt to bind to it. For example:
    # echo "8086 10f5" > /sys/bus/pci/drivers/foo/new_id

    +What: /sys/bus/pci/rescan
    +Date: January 2009
    +Contact: Linux PCI developers <linux-pci@vger.kernel.org>
    +Description:
    + Writing a non-zero value to this attribute will
    + force a rescan of all PCI buses in the system, and
    + re-discover previously removed devices.
    + Depends on CONFIG_HOTPLUG.
    +
    What: /sys/bus/pci/devices/.../vpd
    Date: February 2008
    Contact: Ben Hutchings <bhutchings@solarflare.com>
    diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
    index a5f11ad..62ed864 100644
    --- a/drivers/pci/pci-driver.c
    +++ b/drivers/pci/pci-driver.c
    @@ -973,6 +973,7 @@ struct bus_type pci_bus_type = {
    .remove = pci_device_remove,
    .shutdown = pci_device_shutdown,
    .dev_attrs = pci_dev_attrs,
    + .bus_attrs = pci_bus_attrs,
    .pm = PCI_PM_OPS_PTR,
    };

    diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
    index 1c89298..22dbc65 100644
    --- a/drivers/pci/pci-sysfs.c
    +++ b/drivers/pci/pci-sysfs.c
    @@ -219,6 +219,35 @@ msi_bus_store(struct device *dev, struct device_attribute *attr,
    return count;
    }

    +#ifdef CONFIG_HOTPLUG
    +static DEFINE_MUTEX(pci_remove_rescan_mutex);
    +static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
    + size_t count)
    +{
    + unsigned long val;
    + struct pci_bus *b = NULL;
    +
    + if (strict_strtoul(buf, 0, &val) < 0)
    + return -EINVAL;
    +
    + if (!capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    + if (val) {
    + mutex_lock(&pci_remove_rescan_mutex);
    + while ((b = pci_find_next_bus(b)) != NULL)
    + pci_rescan_bus(b);
    + mutex_unlock(&pci_remove_rescan_mutex);
    + }
    + return count;
    +}
    +
    +struct bus_attribute pci_bus_attrs[] = {
    + __ATTR(rescan, S_IWUSR, NULL, bus_rescan_store),
    + __ATTR_NULL
    +};
    +#endif
    +
    struct device_attribute pci_dev_attrs[] = {
    __ATTR_RO(resource),
    __ATTR_RO(vendor),
    diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
    index 07c0aa5..6dea35f 100644
    --- a/drivers/pci/pci.h
    +++ b/drivers/pci/pci.h
    @@ -136,6 +136,12 @@ extern int pcie_mch_quirk;
    extern struct device_attribute pci_dev_attrs[];
    extern struct device_attribute dev_attr_cpuaffinity;
    extern struct device_attribute dev_attr_cpulistaffinity;
    +#ifdef CONFIG_HOTPLUG
    +extern struct bus_attribute pci_bus_attrs[];
    +#else
    +#define pci_bus_attrs NULL
    +#endif
    +

    /**
    * pci_match_one_device - Tell if a PCI device structure has a matching


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