Commit bc044774 authored by Cyan Ogilvie's avatar Cyan Ogilvie Committed by Jiri Slaby

HID: wiimote: Fix wiimote mp scale linearization

commit d3059673 upstream.

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: default avatarCyan Ogilvie <cyan.ogilvie@gmail.com>
Reviewed-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
parent cb1a03a4
......@@ -1951,9 +1951,11 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
* -----+------------------------------+-----+-----+
* 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.
......@@ -1972,15 +1974,15 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
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;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment