[RFC PATCH 06/10] PCI: Introduce /sys/bus/pci/devices/.../rescan

[Alex Chiang <achiang@hp.com>]

This interface allows the user to force a rescan of the device's
parent bus and all subordinate buses, and rediscover devices removed
earlier from this part of the device tree.

Cc: Trent Piepho <xyzzy@speakeasy.org>
Cc: djwong@us.ibm.com
Reviewed-by: James Cameron <qz@hp.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
---

 Documentation/ABI/testing/sysfs-bus-pci |   10 ++++++++++
 drivers/pci/pci-sysfs.c                 |   22 ++++++++++++++++++++++
 2 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 8c0abc7..f59e963 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -15,6 +15,16 @@ Description:
 		hot-remove the PCI device and any of its children.
 		Depends on CONFIG_HOTPLUG.
 
+What:		/sys/bus/pci/devices/.../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 the device's parent bus and all
+		child buses, and re-discover devices removed earlier
+		from this part of the device tree.
+		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-sysfs.c b/drivers/pci/pci-sysfs.c
index c300242..dcbc8bc 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -220,6 +220,27 @@ msi_bus_store(struct device *dev, struct device_attribute *attr,
 }
 
 #ifdef CONFIG_HOTPLUG
+static ssize_t
+dev_rescan_store(struct device *dev, struct device_attribute *attr,
+	      const char *buf, size_t count)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	unsigned long val;
+
+	if (strict_strtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (val) {
+		pci_scan_child_bus(pdev->bus);
+		pci_bus_add_devices(pdev->bus);
+	}
+
+	return count;
+}
+
 static void remove_callback(void *data)
 {
 	pci_remove_bus_device((struct pci_dev *)data);
@@ -266,6 +287,7 @@ struct device_attribute pci_dev_attrs[] = {
 	__ATTR(msi_bus, 0644, msi_bus_show, msi_bus_store),
 #ifdef CONFIG_HOTPLUG
 	__ATTR(remove, S_IWUSR, NULL, remove_store),
+	__ATTR(rescan, S_IWUSR, NULL, dev_rescan_store),
 #endif
 	__ATTR_NULL,
 };