USB: serial: use kmemdup instead of kmalloc + memcpy

For code neat purpose, we can use kmemdup to replace
kmalloc + memcpy.
Signed-off-by: Slark Xiao <slark_xiao@163.com>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/garmin_gps.c

@@ -988,7 +988,7 @@ static int garmin_write_bulk(struct usb_serial_port *port,
 	garmin_data_p->flags &= ~FLAGS_DROP_DATA;
 	spin_unlock_irqrestore(&garmin_data_p->lock, flags);
 
-	buffer = kmalloc(count, GFP_ATOMIC);
+	buffer = kmemdup(buf, count, GFP_ATOMIC);
 	if (!buffer)
 		return -ENOMEM;
 
@@ -998,8 +998,6 @@ static int garmin_write_bulk(struct usb_serial_port *port,
 		return -ENOMEM;
 	}
 
-	memcpy(buffer, buf, count);
-
 	usb_serial_debug_data(&port->dev, __func__, count, buffer);
 
 	usb_fill_bulk_urb(urb, serial->dev,

drivers/usb/serial/opticon.c

@@ -208,7 +208,7 @@ static int opticon_write(struct tty_struct *tty, struct usb_serial_port *port,
 	priv->outstanding_bytes += count;
 	spin_unlock_irqrestore(&priv->lock, flags);
 
-	buffer = kmalloc(count, GFP_ATOMIC);
+	buffer = kmemdup(buf, count, GFP_ATOMIC);
 	if (!buffer)
 		goto error_no_buffer;
 
@@ -216,8 +216,6 @@ static int opticon_write(struct tty_struct *tty, struct usb_serial_port *port,
 	if (!urb)
 		goto error_no_urb;
 
-	memcpy(buffer, buf, count);
-
 	usb_serial_debug_data(&port->dev, __func__, count, buffer);
 
 	/* The connected devices do not have a bulk write endpoint,

drivers/usb/serial/sierra.c

@@ -453,7 +453,7 @@ static int sierra_write(struct tty_struct *tty, struct usb_serial_port *port,
 		goto error_simple;
 	}
 
-	buffer = kmalloc(writesize, GFP_ATOMIC);
+	buffer = kmemdup(buf, writesize, GFP_ATOMIC);
 	if (!buffer) {
 		retval = -ENOMEM;
 		goto error_no_buffer;
@@ -465,8 +465,6 @@ static int sierra_write(struct tty_struct *tty, struct usb_serial_port *port,
 		goto error_no_urb;
 	}
 
-	memcpy(buffer, buf, writesize);
-
 	usb_serial_debug_data(&port->dev, __func__, writesize, buffer);
 
 	usb_fill_bulk_urb(urb, serial->dev,