HID: nintendo: improve rumble performance and stability

This patch alters the method that the rumble data is sent to the
controller. Rather than using the enable rumble subcommand for this
purpose, the driver now employs the RUMBLE_ONLY output report. This has
the advantage of not needing to receive a subcommand reply (to the major
benefit of reducing IMU latency) and also seems to make the rumble
vibrations more continuous. Perhaps most importantly it reduces
disconnects during times of heavy rumble.
Signed-off-by: Daniel J. Ogorchock <djogorchock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-nintendo.c

@@ -348,6 +348,12 @@ enum joycon_msg_type {
 	JOYCON_MSG_TYPE_SUBCMD,
 };
 
+struct joycon_rumble_output {
+	u8 output_id;
+	u8 packet_num;
+	u8 rumble_data[8];
+} __packed;
+
 struct joycon_subcmd_request {
 	u8 output_id; /* must be 0x01 for subcommand, 0x10 for rumble only */
 	u8 packet_num; /* incremented every send */
@@ -1328,6 +1334,36 @@ static void joycon_parse_report(struct joycon_ctlr *ctlr,
 		joycon_parse_imu_report(ctlr, rep);
 }
 
+static int joycon_send_rumble_data(struct joycon_ctlr *ctlr)
+{
+	int ret;
+	unsigned long flags;
+	struct joycon_rumble_output rumble_output = { 0 };
+
+	spin_lock_irqsave(&ctlr->lock, flags);
+	/*
+	 * If the controller has been removed, just return ENODEV so the LED
+	 * subsystem doesn't print invalid errors on removal.
+	 */
+	if (ctlr->ctlr_state == JOYCON_CTLR_STATE_REMOVED) {
+		spin_unlock_irqrestore(&ctlr->lock, flags);
+		return -ENODEV;
+	}
+	memcpy(rumble_output.rumble_data,
+	       ctlr->rumble_data[ctlr->rumble_queue_tail],
+	       JC_RUMBLE_DATA_SIZE);
+	spin_unlock_irqrestore(&ctlr->lock, flags);
+
+	rumble_output.output_id = JC_OUTPUT_RUMBLE_ONLY;
+	rumble_output.packet_num = ctlr->subcmd_num;
+	if (++ctlr->subcmd_num > 0xF)
+		ctlr->subcmd_num = 0;
+
+	ret = __joycon_hid_send(ctlr->hdev, (u8 *)&rumble_output,
+				sizeof(rumble_output));
+	return ret;
+}
+
 static void joycon_rumble_worker(struct work_struct *work)
 {
 	struct joycon_ctlr *ctlr = container_of(work, struct joycon_ctlr,
@@ -1338,7 +1374,7 @@ static void joycon_rumble_worker(struct work_struct *work)
 
 	while (again) {
 		mutex_lock(&ctlr->output_mutex);
-		ret = joycon_enable_rumble(ctlr);
+		ret = joycon_send_rumble_data(ctlr);
 		mutex_unlock(&ctlr->output_mutex);
 
 		/* -ENODEV means the controller was just unplugged */