kobject: convert hvc_console to use kref, not kobject

hvc_console is using a kobject only for reference counting, nothing
else.  So switch it to use a kref instead, which is all that is needed,
and is much smaller.

Cc: Anton Blanchard <anton@au.ibm.com>
Cc: Paul Mackerras <paulus@au.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ryan S. Arnold <rsa@us.ibm.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/char/hvc_console.c

@@ -27,7 +27,7 @@
 #include <linux/init.h>
 #include <linux/kbd_kern.h>
 #include <linux/kernel.h>
-#include <linux/kobject.h>
+#include <linux/kref.h>
 #include <linux/kthread.h>
 #include <linux/list.h>
 #include <linux/module.h>
@@ -89,7 +89,7 @@ struct hvc_struct {
 	int irq_requested;
 	int irq;
 	struct list_head next;
-	struct kobject kobj; /* ref count & hvc_struct lifetime */
+	struct kref kref; /* ref count & hvc_struct lifetime */
 };
 
 /* dynamic list of hvc_struct instances */
@@ -110,7 +110,7 @@ static int last_hvc = -1;
 
 /*
  * Do not call this function with either the hvc_structs_lock or the hvc_struct
- * lock held.  If successful, this function increments the kobject reference
+ * lock held.  If successful, this function increments the kref reference
  * count against the target hvc_struct so it should be released when finished.
  */
 static struct hvc_struct *hvc_get_by_index(int index)
@@ -123,7 +123,7 @@ static struct hvc_struct *hvc_get_by_index(int index)
 	list_for_each_entry(hp, &hvc_structs, next) {
 		spin_lock_irqsave(&hp->lock, flags);
 		if (hp->index == index) {
-			kobject_get(&hp->kobj);
+			kref_get(&hp->kref);
 			spin_unlock_irqrestore(&hp->lock, flags);
 			spin_unlock(&hvc_structs_lock);
 			return hp;
@@ -242,6 +242,23 @@ static int __init hvc_console_init(void)
 }
 console_initcall(hvc_console_init);
 
+/* callback when the kboject ref count reaches zero. */
+static void destroy_hvc_struct(struct kref *kref)
+{
+	struct hvc_struct *hp = container_of(kref, struct hvc_struct, kref);
+	unsigned long flags;
+
+	spin_lock(&hvc_structs_lock);
+
+	spin_lock_irqsave(&hp->lock, flags);
+	list_del(&(hp->next));
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	spin_unlock(&hvc_structs_lock);
+
+	kfree(hp);
+}
+
 /*
  * hvc_instantiate() is an early console discovery method which locates
  * consoles * prior to the vio subsystem discovering them.  Hotplugged
@@ -261,7 +278,7 @@ int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops)
 	/* make sure no no tty has been registered in this index */
 	hp = hvc_get_by_index(index);
 	if (hp) {
-		kobject_put(&hp->kobj);
+		kref_put(&hp->kref, destroy_hvc_struct);
 		return -1;
 	}
 
@@ -318,9 +335,8 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 	unsigned long flags;
 	int irq = 0;
 	int rc = 0;
-	struct kobject *kobjp;
 
-	/* Auto increments kobject reference if found. */
+	/* Auto increments kref reference if found. */
 	if (!(hp = hvc_get_by_index(tty->index)))
 		return -ENODEV;
 
@@ -341,8 +357,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 	if (irq)
 		hp->irq_requested = 1;
 
-	kobjp = &hp->kobj;
-
 	spin_unlock_irqrestore(&hp->lock, flags);
 	/* check error, fallback to non-irq */
 	if (irq)
@@ -352,7 +366,7 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 	 * If the request_irq() fails and we return an error.  The tty layer
 	 * will call hvc_close() after a failed open but we don't want to clean
 	 * up there so we'll clean up here and clear out the previously set
-	 * tty fields and return the kobject reference.
+	 * tty fields and return the kref reference.
 	 */
 	if (rc) {
 		spin_lock_irqsave(&hp->lock, flags);
@@ -360,7 +374,7 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 		hp->irq_requested = 0;
 		spin_unlock_irqrestore(&hp->lock, flags);
 		tty->driver_data = NULL;
-		kobject_put(kobjp);
+		kref_put(&hp->kref, destroy_hvc_struct);
 		printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
 	}
 	/* Force wakeup of the polling thread */
@@ -372,7 +386,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 static void hvc_close(struct tty_struct *tty, struct file * filp)
 {
 	struct hvc_struct *hp;
-	struct kobject *kobjp;
 	int irq = 0;
 	unsigned long flags;
 
@@ -382,7 +395,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
 	/*
 	 * No driver_data means that this close was issued after a failed
 	 * hvc_open by the tty layer's release_dev() function and we can just
-	 * exit cleanly because the kobject reference wasn't made.
+	 * exit cleanly because the kref reference wasn't made.
 	 */
 	if (!tty->driver_data)
 		return;
@@ -390,7 +403,6 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
 	hp = tty->driver_data;
 	spin_lock_irqsave(&hp->lock, flags);
 
-	kobjp = &hp->kobj;
 	if (--hp->count == 0) {
 		if (hp->irq_requested)
 			irq = hp->irq;
@@ -417,7 +429,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
 		spin_unlock_irqrestore(&hp->lock, flags);
 	}
 
-	kobject_put(kobjp);
+	kref_put(&hp->kref, destroy_hvc_struct);
 }
 
 static void hvc_hangup(struct tty_struct *tty)
@@ -426,7 +438,6 @@ static void hvc_hangup(struct tty_struct *tty)
 	unsigned long flags;
 	int irq = 0;
 	int temp_open_count;
-	struct kobject *kobjp;
 
 	if (!hp)
 		return;
@@ -443,7 +454,6 @@ static void hvc_hangup(struct tty_struct *tty)
 		return;
 	}
 
-	kobjp = &hp->kobj;
 	temp_open_count = hp->count;
 	hp->count = 0;
 	hp->n_outbuf = 0;
@@ -457,7 +467,7 @@ static void hvc_hangup(struct tty_struct *tty)
 		free_irq(irq, hp);
 	while(temp_open_count) {
 		--temp_open_count;
-		kobject_put(kobjp);
+		kref_put(&hp->kref, destroy_hvc_struct);
 	}
 }
 
@@ -729,27 +739,6 @@ static const struct tty_operations hvc_ops = {
 	.chars_in_buffer = hvc_chars_in_buffer,
 };
 
-/* callback when the kboject ref count reaches zero. */
-static void destroy_hvc_struct(struct kobject *kobj)
-{
-	struct hvc_struct *hp = container_of(kobj, struct hvc_struct, kobj);
-	unsigned long flags;
-
-	spin_lock(&hvc_structs_lock);
-
-	spin_lock_irqsave(&hp->lock, flags);
-	list_del(&(hp->next));
-	spin_unlock_irqrestore(&hp->lock, flags);
-
-	spin_unlock(&hvc_structs_lock);
-
-	kfree(hp);
-}
-
-static struct kobj_type hvc_kobj_type = {
-	.release = destroy_hvc_struct,
-};
-
 struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
 					struct hv_ops *ops, int outbuf_size)
 {
@@ -776,8 +765,7 @@ struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
 	hp->outbuf_size = outbuf_size;
 	hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
 
-	kobject_init(&hp->kobj);
-	hp->kobj.ktype = &hvc_kobj_type;
+	kref_init(&hp->kref);
 
 	spin_lock_init(&hp->lock);
 	spin_lock(&hvc_structs_lock);
@@ -806,12 +794,10 @@ struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
 int __devexit hvc_remove(struct hvc_struct *hp)
 {
 	unsigned long flags;
-	struct kobject *kobjp;
 	struct tty_struct *tty;
 
 	spin_lock_irqsave(&hp->lock, flags);
 	tty = hp->tty;
-	kobjp = &hp->kobj;
 
 	if (hp->index < MAX_NR_HVC_CONSOLES)
 		vtermnos[hp->index] = -1;
@@ -821,12 +807,12 @@ int __devexit hvc_remove(struct hvc_struct *hp)
 	spin_unlock_irqrestore(&hp->lock, flags);
 
 	/*
-	 * We 'put' the instance that was grabbed when the kobject instance
-	 * was initialized using kobject_init().  Let the last holder of this
-	 * kobject cause it to be removed, which will probably be the tty_hangup
+	 * We 'put' the instance that was grabbed when the kref instance
+	 * was initialized using kref_init().  Let the last holder of this
+	 * kref cause it to be removed, which will probably be the tty_hangup
 	 * below.
 	 */
-	kobject_put(kobjp);
+	kref_put(&hp->kref, destroy_hvc_struct);
 
 	/*
 	 * This function call will auto chain call hvc_hangup.  The tty should