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Commit d3059673 authored by Cyan Ogilvie's avatar Cyan Ogilvie Committed by Jiri Kosina
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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: 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>
parent d66435cc

drivers/hid/hid-wiimote-modules.c

+8 −6
Original line number Diff line number Diff line
@@ -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;