Input: xpad - update Xbox One Force Feedback Support

There's apparently a serial number woven into both input and output
packets; neglecting to specify a valid serial number causes the controller
to ignore the rumble packets.

The scale of the rumble was also apparently halved in the packets.

The initialization packet had to be changed to allow force feedback to
work.

see https://github.com/paroj/xpad/issues/7 for details.
Signed-off-by: Pavel Rojtberg <rojtberg@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/joystick/xpad.c

@@ -348,6 +348,7 @@ struct usb_xpad {
 	struct urb *irq_out;		/* urb for interrupt out report */
 	bool irq_out_active;		/* we must not use an active URB */
 	unsigned char *odata;		/* output data */
+	u8 odata_serial;		/* serial number for xbox one protocol */
 	dma_addr_t odata_dma;
 	spinlock_t odata_lock;
 
@@ -923,7 +924,10 @@ static int xpad_start_xbox_one(struct usb_xpad *xpad)
 	/* Xbox one controller needs to be initialized. */
 	packet->data[0] = 0x05;
 	packet->data[1] = 0x20;
-	packet->len = 2;
+	packet->data[2] = xpad->odata_serial++; /* packet serial */
+	packet->data[3] = 0x01; /* rumble bit enable?  */
+	packet->data[4] = 0x00;
+	packet->len = 5;
 	packet->pending = true;
 
 	/* Reset the sequence so we send out start packet first */
@@ -998,17 +1002,18 @@ static int xpad_play_effect(struct input_dev *dev, void *data, struct ff_effect
 	case XTYPE_XBOXONE:
 		packet->data[0] = 0x09; /* activate rumble */
 		packet->data[1] = 0x08;
-		packet->data[2] = 0x00;
+		packet->data[2] = xpad->odata_serial++;
 		packet->data[3] = 0x08; /* continuous effect */
 		packet->data[4] = 0x00; /* simple rumble mode */
 		packet->data[5] = 0x03; /* L and R actuator only */
 		packet->data[6] = 0x00; /* TODO: LT actuator */
 		packet->data[7] = 0x00; /* TODO: RT actuator */
-		packet->data[8] = strong / 256;	/* left actuator */
-		packet->data[9] = weak / 256;	/* right actuator */
+		packet->data[8] = strong / 512;	/* left actuator */
+		packet->data[9] = weak / 512;	/* right actuator */
 		packet->data[10] = 0x80;	/* length of pulse */
 		packet->data[11] = 0x00;	/* stop period of pulse */
-		packet->len = 12;
+		packet->data[12] = 0x00;
+		packet->len = 13;
 		packet->pending = true;
 		break;