HID: wiimote: Fix wiimote mp scale linearization
The wiimote motion plus gyros use two scales to report fast and slow
rotation - below 440 deg/s uses 8192/440 units / deg/s, and above uses
8192/2000 units / deg/s.
Previously this driver attempted to linearize the two by scaling the fast
rate by 18 and the slow by 9, but this results in a scale of
8192*9/440 = ~167.564 for slow and 8192*18/2000 = 73.728 for fast.
Correct the fast motion scale factor so that both report ~167.564
units / deg/s
Signed-off-by: Cyan Ogilvie <cyan.ogilvie@gmail.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-wiimote-modules.c b/drivers/hid/hid-wiimote-modules.c
index 4390eee..c830ed3 100644
--- a/drivers/hid/hid-wiimote-modules.c
+++ b/drivers/hid/hid-wiimote-modules.c
@@ -2049,9 +2049,11 @@
* -----+------------------------------+-----+-----+
* The single bits Yaw, Roll, Pitch in the lower right corner specify
* whether the wiimote is rotating fast (0) or slow (1). Speed for slow
- * roation is 440 deg/s and for fast rotation 2000 deg/s. To get a
- * linear scale we multiply by 2000/440 = ~4.5454 which is 18 for fast
- * and 9 for slow.
+ * roation is 8192/440 units / deg/s and for fast rotation 8192/2000
+ * units / deg/s. To get a linear scale for fast rotation we multiply
+ * by 2000/440 = ~4.5454 and scale both fast and slow by 9 to match the
+ * previous scale reported by this driver.
+ * This leaves a linear scale with 8192*9/440 (~167.564) units / deg/s.
* If the wiimote is not rotating the sensor reports 2^13 = 8192.
* Ext specifies whether an extension is connected to the motionp.
* which is parsed by wiimote-core.
@@ -2070,15 +2072,15 @@
z -= 8192;
if (!(ext[3] & 0x02))
- x *= 18;
+ x = (x * 2000 * 9) / 440;
else
x *= 9;
if (!(ext[4] & 0x02))
- y *= 18;
+ y = (y * 2000 * 9) / 440;
else
y *= 9;
if (!(ext[3] & 0x01))
- z *= 18;
+ z = (z * 2000 * 9) / 440;
else
z *= 9;