diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 7f6f3ab5b8a6770060cae81445aecd9e88d1cc48..f3803fa7c0077567a1399f5b56136639d651bd2f 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -173,7 +173,7 @@ static int acm_wb_alloc(struct acm *acm)
 	for (;;) {
 		wb = &acm->wb[wbn];
 		if (!wb->use) {
-			wb->use = 1;
+			wb->use = true;
 			wb->len = 0;
 			return wbn;
 		}
@@ -191,7 +191,8 @@ static int acm_wb_is_avail(struct acm *acm)
 	n = ACM_NW;
 	spin_lock_irqsave(&acm->write_lock, flags);
 	for (i = 0; i < ACM_NW; i++)
-		n -= acm->wb[i].use;
+		if(acm->wb[i].use)
+			n--;
 	spin_unlock_irqrestore(&acm->write_lock, flags);
 	return n;
 }
@@ -201,7 +202,7 @@ static int acm_wb_is_avail(struct acm *acm)
  */
 static void acm_write_done(struct acm *acm, struct acm_wb *wb)
 {
-	wb->use = 0;
+	wb->use = false;
 	acm->transmitting--;
 	usb_autopm_put_interface_async(acm->control);
 }
@@ -741,7 +742,7 @@ static void acm_port_shutdown(struct tty_port *port)
 		if (!urb)
 			break;
 		wb = urb->context;
-		wb->use = 0;
+		wb->use = false;
 		usb_autopm_put_interface_async(acm->control);
 	}
 
@@ -792,7 +793,7 @@ static int acm_tty_write(struct tty_struct *tty,
 	wb = &acm->wb[wbn];
 
 	if (!acm->dev) {
-		wb->use = 0;
+		wb->use = false;
 		spin_unlock_irqrestore(&acm->write_lock, flags);
 		return -ENODEV;
 	}
@@ -804,7 +805,7 @@ static int acm_tty_write(struct tty_struct *tty,
 
 	stat = usb_autopm_get_interface_async(acm->control);
 	if (stat) {
-		wb->use = 0;
+		wb->use = false;
 		spin_unlock_irqrestore(&acm->write_lock, flags);
 		return stat;
 	}
diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index cd5e9d8ab237588bb2aa9cd615b9b1356b59e1cc..a50ea39110424259e2d06f128b2fc95cb550c4d4 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -64,12 +64,12 @@
 #define ACM_NR  16
 
 struct acm_wb {
-	unsigned char *buf;
+	u8 *buf;
 	dma_addr_t dmah;
-	int len;
-	int use;
+	unsigned int len;
 	struct urb		*urb;
 	struct acm		*instance;
+	bool use;
 };
 
 struct acm_rb {