PCI: pciehp: Rename duplicate slot name N as N-1, N-2, N-M...

Commit 3800345f723fd130d50434d4717b99d4a9f383c8 (pciehp: fix slot name)
introduces the pciehp_slot_with_bus module parameter, which was intended
to help work around broken firmware that assigns the same name to multiple
slots.

Commit 9e4f2e8d4ddb04ad16a3828cd9a369a5a5287009 (pciehp: add message about
pciehp_slot_with_bus option) tells the user to use the above parameter
in the event of a name collision.

This approach is sub-optimal because it requires too much work from
the user.

Instead, let's rename the slot on behalf of the user. If firmware
assigns the name N to multiple slots, then:

The first registered slot is assigned N
The second registered slot is assigned N-1
The third registered slot is assigned N-2
The Mth registered slot becomes N-M

In the event we overflow the slot->name parameter, we report an
error to the user.

This is a temporary fix until the entire PCI core can be reworked
such that individual drivers no longer have to manage their own
slot names.

Tested-by: Kenji Kaneshige <[e-mail]>
Acked-by: Kenji Kaneshige <[e-mail]>
Signed-off-by: Alex Chiang <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

drivers/pci/hotplug/pciehp.h

···
 extern int pciehp_poll_time;
 extern int pciehp_debug;
 extern int pciehp_force;
-extern int pciehp_slot_with_bus;
 extern struct workqueue_struct *pciehp_wq;
 
 #define dbg(format, arg...)						\

drivers/pci/hotplug/pciehp_core.c

···
 int pciehp_poll_mode;
 int pciehp_poll_time;
 int pciehp_force;
-int pciehp_slot_with_bus;
 struct workqueue_struct *pciehp_wq;
 
 #define DRIVER_VERSION	"0.4"
···
 module_param(pciehp_poll_mode, bool, 0644);
 module_param(pciehp_poll_time, int, 0644);
 module_param(pciehp_force, bool, 0644);
-module_param(pciehp_slot_with_bus, bool, 0644);
 MODULE_PARM_DESC(pciehp_debug, "Debugging mode enabled or not");
 MODULE_PARM_DESC(pciehp_poll_mode, "Using polling mechanism for hot-plug events or not");
 MODULE_PARM_DESC(pciehp_poll_time, "Polling mechanism frequency, in seconds");
 MODULE_PARM_DESC(pciehp_force, "Force pciehp, even if _OSC and OSHP are missing");
-MODULE_PARM_DESC(pciehp_slot_with_bus, "Use bus number in the slot name");
 
 #define PCIE_MODULE_NAME "pciehp"
 
···
 	struct slot *slot;
 	struct hotplug_slot *hotplug_slot;
 	struct hotplug_slot_info *info;
+	int len, dup = 1;
 	int retval = -ENOMEM;
 
 	list_for_each_entry(slot, &ctrl->slot_list, slot_list) {
···
 		dbg("Registering bus=%x dev=%x hp_slot=%x sun=%x "
 		    "slot_device_offset=%x\n", slot->bus, slot->device,
 		    slot->hp_slot, slot->number, ctrl->slot_device_offset);
+duplicate_name:
 		retval = pci_hp_register(hotplug_slot,
 					 ctrl->pci_dev->subordinate,
 					 slot->device);
 		if (retval) {
+			/*
+			 * If slot N already exists, we'll try to create
+			 * slot N-1, N-2 ... N-M, until we overflow.
+			 */
+			if (retval == -EEXIST) {
+				len = snprintf(slot->name, SLOT_NAME_SIZE,
+					       "%d-%d", slot->number, dup++);
+				if (len < SLOT_NAME_SIZE)
+					goto duplicate_name;
+				else
+					err("duplicate slot name overflow\n");
+			}
 			err("pci_hp_register failed with error %d\n", retval);
-			if (retval == -EEXIST)
-				err("Failed to register slot because of name "
-				    "collision. Try \'pciehp_slot_with_bus\' "
-				    "module option.\n");
 			goto error_info;
 		}
 		/* create additional sysfs entries */

drivers/pci/hotplug/pciehp_hpc.c

···
 	pciehp_free_irq(ctrl);
 }
 
-static void make_slot_name(struct slot *slot)
-{
-	if (pciehp_slot_with_bus)
-		snprintf(slot->name, SLOT_NAME_SIZE, "%04d_%04d",
-			 slot->bus, slot->number);
-	else
-		snprintf(slot->name, SLOT_NAME_SIZE, "%d", slot->number);
-}
-
 static int pcie_init_slot(struct controller *ctrl)
 {
 	struct slot *slot;
···
 	slot->device = ctrl->slot_device_offset + slot->hp_slot;
 	slot->hpc_ops = ctrl->hpc_ops;
 	slot->number = ctrl->first_slot;
-	make_slot_name(slot);
+	snprintf(slot->name, SLOT_NAME_SIZE, "%d", slot->number);
 	mutex_init(&slot->lock);
 	INIT_DELAYED_WORK(&slot->work, pciehp_queue_pushbutton_work);
 	list_add(&slot->slot_list, &ctrl->slot_list);