Hi On Wed, Mar 16, 2016 at 5:59 PM, Cyan Ogilvie <cyan.ogilvie@xxxxxxxxx> wrote: > 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@xxxxxxxxx> > --- > drivers/hid/hid-wiimote-modules.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > 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 @@ 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. Oh dear! My initial reasoning was completely off. I somehow upscaled 4.5 to 18, and 1 to 9, when it should have been 1 to 4. Oops! > + * 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; So 2000/440 ~= 4.5, so this is exactly what the initial comment said. Patch looks good to me: Reviewed-by: David Herrmann <dh.herrmann@xxxxxxxxx> Thanks David > else > z *= 9; > > -- > 2.1.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
