PCI: Introduce /sys/bus/pci/devices/.../rescan

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 <[e-mail]>
Signed-off-by: Alex Chiang <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

Documentation/ABI/testing/sysfs-bus-pci

···
 		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 <[e-mail]>
+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 <[e-mail]>

drivers/pci/pci-sysfs.c

···
 	__ATTR_NULL
 };
 
+static ssize_t
+dev_rescan_store(struct device *dev, struct device_attribute *attr,
+		 const char *buf, size_t count)
+{
+	unsigned long val;
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	if (strict_strtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (val) {
+		mutex_lock(&pci_remove_rescan_mutex);
+		pci_rescan_bus(pdev->bus);
+		mutex_unlock(&pci_remove_rescan_mutex);
+	}
+	return count;
+}
+
 static void remove_callback(struct device *dev)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
···
 	__ATTR(msi_bus, 0644, msi_bus_show, msi_bus_store),
 #ifdef CONFIG_HOTPLUG
 	__ATTR(remove, (S_IWUSR|S_IWGRP), NULL, remove_store),
+	__ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, dev_rescan_store),
 #endif
 	__ATTR_NULL,
 };