driver model: change struct device::present to enumerated value with multiple states.

Adapted from Greg KH: 

- add multiple possible enumerated states a device can be in: UNINITIALIZED, INITIALIZED,
  REGISTERED, and GONE.
- Check whether device is INITIALIZED or REGISTERED in device_present().
- Change struct device::current_state to ::power_state to better reflect what it is.

drivers/base/core.c

@@ -33,7 +33,7 @@ int device_add(struct device *dev)
 		return -EINVAL;
 
 	down(&device_sem);
-	dev->present = 1;
+	dev->state = DEVICE_REGISTERED;
 	if (dev->parent) {
 		list_add_tail(&dev->g_list,&dev->parent->g_list);
 		list_add_tail(&dev->node,&dev->parent->children);
@@ -77,6 +77,7 @@ void device_initialize(struct device *dev)
 	INIT_LIST_HEAD(&dev->intf_list);
 	spin_lock_init(&dev->lock);
 	atomic_set(&dev->refcount,1);
+	dev->state = DEVICE_INITIALIZED;
 	if (dev->parent)
 		get_device(dev->parent);
 }
@@ -112,7 +113,7 @@ struct device * get_device(struct device * dev)
 {
 	struct device * ret = dev;
 	down(&device_sem);
-	if (dev && dev->present && atomic_read(&dev->refcount) > 0)
+	if (device_present(dev) && atomic_read(&dev->refcount) > 0)
 		atomic_inc(&dev->refcount);
 	else
 		ret = NULL;
@@ -135,7 +136,7 @@ void put_device(struct device * dev)
 	list_del_init(&dev->g_list);
 	up(&device_sem);
 
-	BUG_ON(dev->present);
+	BUG_ON((dev->state != DEVICE_GONE));
 
 	device_del(dev);
 }
@@ -177,7 +178,7 @@ void device_del(struct device * dev)
 void device_unregister(struct device * dev)
 {
 	down(&device_sem);
-	dev->present = 0;
+	dev->state = DEVICE_GONE;
 	up(&device_sem);
 
 	pr_debug("DEV: Unregistering device. ID = '%s', name = '%s'\n",

drivers/base/interface.c

@@ -19,7 +19,7 @@ static DEVICE_ATTR(name,S_IRUGO,device_read_name,NULL);
 static ssize_t
 device_read_power(struct device * dev, char * page, size_t count, loff_t off)
 {
-	return off ? 0 : sprintf(page,"%d\n",dev->current_state);
+	return off ? 0 : sprintf(page,"%d\n",dev->power_state);
 }
 
 static ssize_t

include/linux/device.h

@@ -48,6 +48,13 @@ enum {
 	RESUME_ENABLE,
 };
 
+enum device_state {
+	DEVICE_UNINITIALIZED	= 0,
+	DEVICE_INITIALIZED	= 1,
+	DEVICE_REGISTERED	= 2,
+	DEVICE_GONE		= 3,
+};
+
 struct device;
 struct device_driver;
 struct device_class;
@@ -288,8 +295,8 @@ struct device {
 	void		*platform_data;	/* Platform specific data (e.g. ACPI,
 					   BIOS data relevant to device) */
 
-	u32		present;
-	u32		current_state;  /* Current operating state. In
+	enum device_state state;
+	u32		power_state;  /* Current operating state. In
 					   ACPI-speak, this is D0-D3, D0
 					   being fully functional, and D3
 					   being off. */
@@ -363,7 +370,7 @@ extern int (*platform_notify_remove)(struct device * dev);
 
 static inline int device_present(struct device * dev)
 {
-	return (dev && dev->present == 1);
+	return (dev && (dev->state == DEVICE_INITIALIZED || dev->state == DEVICE_REGISTERED));
 }
 
 /* device and bus locking helpers.