W1: w1_int.c use first available master number

Follow the example of other devices (like the joystick device).  Pick the
first available id for each detected device.  Currently for USB devices,
suspending and resuming would cause the number to increment.
Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/w1/w1_int.c

@@ -29,7 +29,6 @@
 #include "w1_netlink.h"
 #include "w1_int.h"
 
-static u32 w1_ids = 1;
 static int w1_search_count = -1; /* Default is continual scan */
 module_param_named(search_count, w1_search_count, int, 0);
 
@@ -102,9 +101,10 @@ static void w1_free_dev(struct w1_master *dev)
 
 int w1_add_master_device(struct w1_bus_master *master)
 {
-	struct w1_master *dev;
+	struct w1_master *dev, *entry;
 	int retval = 0;
 	struct w1_netlink_msg msg;
+	int id, found;
 
         /* validate minimum functionality */
         if (!(master->touch_bit && master->reset_bus) &&
@@ -126,13 +126,33 @@ int w1_add_master_device(struct w1_bus_master *master)
 		master->set_pullup = NULL;
 	}
 
-	dev = w1_alloc_dev(w1_ids++, w1_max_slave_count, w1_max_slave_ttl, &w1_master_driver, &w1_master_device);
-	if (!dev)
+	/* Lock until the device is added (or not) to w1_masters. */
+	mutex_lock(&w1_mlock);
+	/* Search for the first available id (starting at 1). */
+	id = 0;
+	do {
+		++id;
+		found = 0;
+		list_for_each_entry(entry, &w1_masters, w1_master_entry) {
+			if (entry->id == id) {
+				found = 1;
+				break;
+			}
+		}
+	} while (found);
+
+	dev = w1_alloc_dev(id, w1_max_slave_count, w1_max_slave_ttl,
+		&w1_master_driver, &w1_master_device);
+	if (!dev) {
+		mutex_unlock(&w1_mlock);
 		return -ENOMEM;
+	}
 
 	retval =  w1_create_master_attributes(dev);
-	if (retval)
+	if (retval) {
+		mutex_unlock(&w1_mlock);
 		goto err_out_free_dev;
+	}
 
 	memcpy(dev->bus_master, master, sizeof(struct w1_bus_master));
 
@@ -144,10 +164,10 @@ int w1_add_master_device(struct w1_bus_master *master)
 		dev_err(&dev->dev,
 			 "Failed to create new kernel thread. err=%d\n",
 			 retval);
+		mutex_unlock(&w1_mlock);
 		goto err_out_rm_attr;
 	}
 
-	mutex_lock(&w1_mlock);
 	list_add(&dev->w1_master_entry, &w1_masters);
 	mutex_unlock(&w1_mlock);