powerpc: hv{cs, si}_close() both unsigned hp->count and hvcsd->open_count cannot be negative

[roel kluin <roel.kluin@gmail.com>]

unsigned hp->count and hvcsd->open_count cannot be negative

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
Both members of respectively struct hvcs_struct, see
vi drivers/char/hvcs.c +262

and struct hvcs_struct, see
vi drivers/char/hvsi.c +70

diff --git a/drivers/char/hvcs.c b/drivers/char/hvcs.c
index 473d9b1..b228b84 100644
--- a/drivers/char/hvcs.c
+++ b/drivers/char/hvcs.c
@@ -1222,7 +1222,8 @@ static void hvcs_close(struct tty_struct *tty, struct file *filp)
 	hvcsd = tty->driver_data;
 
 	spin_lock_irqsave(&hvcsd->lock, flags);
-	if (--hvcsd->open_count == 0) {
+	if (hvcsd->open_count == 1) {
+		hvcsd->open_count--;
 
 		vio_disable_interrupts(hvcsd->vdev);
 
@@ -1248,7 +1249,9 @@ static void hvcs_close(struct tty_struct *tty, struct file *filp)
 		free_irq(irq, hvcsd);
 		kref_put(&hvcsd->kref, destroy_hvcs_struct);
 		return;
-	} else if (hvcsd->open_count < 0) {
+	} else if (hvcsd->open_count > 1) {
+		hvcsd->open_count--;
+	} else {
 		printk(KERN_ERR "HVCS: vty-server@%X open_count: %d"
 				" is missmanaged.\n",
 		hvcsd->vdev->unit_address, hvcsd->open_count);
diff --git a/drivers/char/hvsi.c b/drivers/char/hvsi.c
index 59c6f9a..d46bccd 100644
--- a/drivers/char/hvsi.c
+++ b/drivers/char/hvsi.c
@@ -875,7 +875,8 @@ static void hvsi_close(struct tty_struct *tty, struct file *filp)
 
 	spin_lock_irqsave(&hp->lock, flags);
 
-	if (--hp->count == 0) {
+	if (hp->count == 1) {
+		hp->count--;
 		hp->tty = NULL;
 		hp->inbuf_end = hp->inbuf; /* discard remaining partial packets */
 
@@ -908,7 +909,9 @@ static void hvsi_close(struct tty_struct *tty, struct file *filp)
 
 			spin_lock_irqsave(&hp->lock, flags);
 		}
-	} else if (hp->count < 0)
+	} else if (hp->count > 1)
+		hp->count--;
+	else
 		printk(KERN_ERR "hvsi_close %lu: oops, count is %d\n",
 		       hp - hvsi_ports, hp->count);