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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>
This commit is contained in:
Cyan Ogilvie 2016-03-16 18:59:41 +02:00 committed by Jiri Kosina
parent d66435cc7d
commit d30596737e
1 changed files with 8 additions and 6 deletions
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14
drivers/hid/hid-wiimote-modules.c
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@ -2049,9 +2049,11 @@ 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.
@ -2070,15 +2072,15 @@ 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;