linux-kernel - [PATCH 4.4 46/86] Input: xpad - fix Xbox One rumble stopping after 2.5 secs

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Date:   Thu, 29 Nov 2018 15:12:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Cameron Gutman <aicommander@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 46/86] Input: xpad - fix Xbox One rumble stopping after 2.5 secs

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit ae3b4469dbcd3b842a9fd20940946e4d092d8731 ]

Unlike previous Xbox pads, the Xbox One pad doesn't have "sticky" rumble
packets. The duration is encoded into the command and expiration is handled
by the pad firmware.

ff-memless needs pseudo-sticky behavior for rumble effects to behave
properly for long duration effects. We already specify the maximum rumble
on duration in the command packets, but it's still only good for about 2.5
seconds of rumble. This is easily reproducible running fftest's sine
vibration test.

It turns out there's a repeat count encoded in the rumble command. We can
abuse that to get the pseudo-sticky behavior needed for rumble to behave as
expected for effects with long duration.

By my math, this change should allow a single ff_effect to rumble for 10
minutes straight, which should be more than enough for most needs.

Signed-off-by: Cameron Gutman <aicommander@...il.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/input/joystick/xpad.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
index 4dc8befc92e4..b9f48d4e155a 100644
--- a/drivers/input/joystick/xpad.c
+++ b/drivers/input/joystick/xpad.c
@@ -1047,9 +1047,9 @@ static int xpad_play_effect(struct input_dev *dev, void *data, struct ff_effect
 		packet->data[7] = 0x00;
 		packet->data[8] = strong / 512;	/* left actuator */
 		packet->data[9] = weak / 512;	/* right actuator */
-		packet->data[10] = 0xFF;
-		packet->data[11] = 0x00;
-		packet->data[12] = 0x00;
+		packet->data[10] = 0xFF; /* on period */
+		packet->data[11] = 0x00; /* off period */
+		packet->data[12] = 0xFF; /* repeat count */
 		packet->len = 13;
 		packet->pending = true;
 		break;
-- 
2.17.1