PCI hotplug: create symlink to hotplug driver module

Create symbolic link to hotplug driver module in the PCI slot
directory (/sys/bus/pci/slots/<SLOT#>). In the past, we need to load
hotplug drivers one by one to identify the hotplug driver that handles
the slot, and it was very inconvenient especially for trouble shooting.
With this change, we can easily identify the hotplug driver.

Signed-off-by: Taku Izumi <izumi.taku@jp.fujitsu.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Reviewed-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Documentation/ABI/testing/sysfs-bus-pci

@@ -122,3 +122,10 @@ Description:
 		This symbolic link appears when a device is a Virtual Function.
 		The symbolic link points to the PCI device sysfs entry of the
 		Physical Function this device associates with.
+
+What:		/sys/bus/pci/slots/.../module
+Date:		June 2009
+Contact:	linux-pci@vger.kernel.org
+Description:
+		This symbolic link points to the PCI hotplug controller driver
+		module that manages the hotplug slot.

drivers/pci/hotplug/pci_hotplug_core.c

@@ -424,6 +424,9 @@ static int fs_add_slot(struct pci_slot *slot)
 {
 	int retval = 0;
 
+	/* Create symbolic link to the hotplug driver module */
+	pci_hp_create_module_link(slot);
+
 	if (has_power_file(slot)) {
 		retval = sysfs_create_file(&slot->kobj,
 					   &hotplug_slot_attr_power.attr);
@@ -498,6 +501,7 @@ exit_attention:
 	if (has_power_file(slot))
 		sysfs_remove_file(&slot->kobj, &hotplug_slot_attr_power.attr);
 exit_power:
+	pci_hp_remove_module_link(slot);
 exit:
 	return retval;
 }
@@ -528,6 +532,8 @@ static void fs_remove_slot(struct pci_slot *slot)
 
 	if (has_test_file(slot))
 		sysfs_remove_file(&slot->kobj, &hotplug_slot_attr_test.attr);
+
+	pci_hp_remove_module_link(slot);
 }
 
 static struct hotplug_slot *get_slot_from_name (const char *name)
@@ -544,10 +550,10 @@ static struct hotplug_slot *get_slot_from_name (const char *name)
 }
 
 /**
- * pci_hp_register - register a hotplug_slot with the PCI hotplug subsystem
+ * __pci_hp_register - register a hotplug_slot with the PCI hotplug subsystem
  * @bus: bus this slot is on
  * @slot: pointer to the &struct hotplug_slot to register
- * @slot_nr: slot number
+ * @devnr: device number
  * @name: name registered with kobject core
  *
  * Registers a hotplug slot with the pci hotplug subsystem, which will allow
@@ -555,8 +561,9 @@ static struct hotplug_slot *get_slot_from_name (const char *name)
  *
  * Returns 0 if successful, anything else for an error.
  */
-int pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus, int slot_nr,
-			const char *name)
+int __pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus,
+		      int devnr, const char *name,
+		      struct module *owner, const char *mod_name)
 {
 	int result;
 	struct pci_slot *pci_slot;
@@ -571,14 +578,16 @@ int pci_hp_register(struct hotplug_slot *slot, struct pci_bus *bus, int slot_nr,
 		return -EINVAL;
 	}
 
-	mutex_lock(&pci_hp_mutex);
+	slot->ops->owner = owner;
+	slot->ops->mod_name = mod_name;
 
+	mutex_lock(&pci_hp_mutex);
 	/*
 	 * No problems if we call this interface from both ACPI_PCI_SLOT
 	 * driver and call it here again. If we've already created the
 	 * pci_slot, the interface will simply bump the refcount.
 	 */
-	pci_slot = pci_create_slot(bus, slot_nr, name, slot);
+	pci_slot = pci_create_slot(bus, devnr, name, slot);
 	if (IS_ERR(pci_slot)) {
 		result = PTR_ERR(pci_slot);
 		goto out;
@@ -688,6 +697,6 @@ MODULE_LICENSE("GPL");
 module_param(debug, bool, 0644);
 MODULE_PARM_DESC(debug, "Debugging mode enabled or not");
 
-EXPORT_SYMBOL_GPL(pci_hp_register);
+EXPORT_SYMBOL_GPL(__pci_hp_register);
 EXPORT_SYMBOL_GPL(pci_hp_deregister);
 EXPORT_SYMBOL_GPL(pci_hp_change_slot_info);

drivers/pci/slot.c

@@ -307,6 +307,45 @@ void pci_destroy_slot(struct pci_slot *slot)
 }
 EXPORT_SYMBOL_GPL(pci_destroy_slot);
 
+#if defined(CONFIG_HOTPLUG_PCI) || defined(CONFIG_HOTPLUG_PCI_MODULE)
+#include <linux/pci_hotplug.h>
+/**
+ * pci_hp_create_link - create symbolic link to the hotplug driver module.
+ * @slot: struct pci_slot
+ *
+ * Helper function for pci_hotplug_core.c to create symbolic link to
+ * the hotplug driver module.
+ */
+void pci_hp_create_module_link(struct pci_slot *pci_slot)
+{
+	struct hotplug_slot *slot = pci_slot->hotplug;
+	struct kobject *kobj = NULL;
+	int no_warn;
+
+	if (!slot || !slot->ops)
+		return;
+	kobj = kset_find_obj(module_kset, slot->ops->mod_name);
+	if (!kobj)
+		return;
+	no_warn = sysfs_create_link(&pci_slot->kobj, kobj, "module");
+	kobject_put(kobj);
+}
+EXPORT_SYMBOL_GPL(pci_hp_create_module_link);
+
+/**
+ * pci_hp_remove_link - remove symbolic link to the hotplug driver module.
+ * @slot: struct pci_slot
+ *
+ * Helper function for pci_hotplug_core.c to remove symbolic link to
+ * the hotplug driver module.
+ */
+void pci_hp_remove_module_link(struct pci_slot *pci_slot)
+{
+	sysfs_remove_link(&pci_slot->kobj, "module");
+}
+EXPORT_SYMBOL_GPL(pci_hp_remove_module_link);
+#endif
+
 static int pci_slot_init(void)
 {
 	struct kset *pci_bus_kset;

include/linux/pci.h

@@ -1261,5 +1261,10 @@ static inline irqreturn_t pci_sriov_migration(struct pci_dev *dev)
 }
 #endif
 
+#if defined(CONFIG_HOTPLUG_PCI) || defined(CONFIG_HOTPLUG_PCI_MODULE)
+extern void pci_hp_create_module_link(struct pci_slot *pci_slot);
+extern void pci_hp_remove_module_link(struct pci_slot *pci_slot);
+#endif
+
 #endif /* __KERNEL__ */
 #endif /* LINUX_PCI_H */

include/linux/pci_hotplug.h

@@ -69,6 +69,7 @@ enum pcie_link_speed {
 /**
  * struct hotplug_slot_ops -the callbacks that the hotplug pci core can use
  * @owner: The module owner of this structure
+ * @mod_name: The module name (KBUILD_MODNAME) of this structure
  * @enable_slot: Called when the user wants to enable a specific pci slot
  * @disable_slot: Called when the user wants to disable a specific pci slot
  * @set_attention_status: Called to set the specific slot's attention LED to
@@ -101,6 +102,7 @@ enum pcie_link_speed {
  */
 struct hotplug_slot_ops {
 	struct module *owner;
+	const char *mod_name;
 	int (*enable_slot)		(struct hotplug_slot *slot);
 	int (*disable_slot)		(struct hotplug_slot *slot);
 	int (*set_attention_status)	(struct hotplug_slot *slot, u8 value);
@@ -159,12 +161,21 @@ static inline const char *hotplug_slot_name(const struct hotplug_slot *slot)
 	return pci_slot_name(slot->pci_slot);
 }
 
-extern int pci_hp_register(struct hotplug_slot *, struct pci_bus *, int nr,
-			   const char *name);
+extern int __pci_hp_register(struct hotplug_slot *slot, struct pci_bus *pbus,
+			     int nr, const char *name,
+			     struct module *owner, const char *mod_name);
 extern int pci_hp_deregister(struct hotplug_slot *slot);
 extern int __must_check pci_hp_change_slot_info	(struct hotplug_slot *slot,
 						 struct hotplug_slot_info *info);
 
+static inline int pci_hp_register(struct hotplug_slot *slot,
+				  struct pci_bus *pbus,
+				  int devnr, const char *name)
+{
+	return __pci_hp_register(slot, pbus, devnr, name,
+				 THIS_MODULE, KBUILD_MODNAME);
+}
+
 /* PCI Setting Record (Type 0) */
 struct hpp_type0 {
 	u32 revision;