HID: wiimote: add pro-controller analog stick calibration

The analog sticks of the pro-controller might report slightly off values.
To guarantee a uniform setup, we now calibrate analog-stick values during
pro-controller setup.

Unfortunately, the pro-controller fails during normal EEPROM reads and I
couldn't figure out whether there are any calibration values stored on the
device. Therefore, we now use the first values reported by the device (iff
they are not _way_ off, which would indicate movement) to initialize the
calibration values. To allow users to change this calibration data, we
provide a pro_calib sysfs attribute.

We also change the "flat" values so user-space correctly smoothes our
data. It makes slightly off zero-positions less visible while still
guaranteeing highly precise movement reports. Note that the pro controller
reports zero-positions in a quite huge range (at least: -100 to +100).

Reported-by: Rafael Brune <mail@rbrune.de>
Tested-by: Rafael Brune <mail@rbrune.de>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-wiimote.h

@@ -46,6 +46,7 @@
 #define WIIPROTO_FLAG_DRM_LOCKED	0x8000
 #define WIIPROTO_FLAG_BUILTIN_MP	0x010000
 #define WIIPROTO_FLAG_NO_MP		0x020000
+#define WIIPROTO_FLAG_PRO_CALIB_DONE	0x040000
 
 #define WIIPROTO_FLAGS_LEDS (WIIPROTO_FLAG_LED1 | WIIPROTO_FLAG_LED2 | \
 					WIIPROTO_FLAG_LED3 | WIIPROTO_FLAG_LED4)
@@ -135,6 +136,7 @@ struct wiimote_state {
 
 	/* calibration/cache data */
 	__u16 calib_bboard[4][3];
+	__s16 calib_pro_sticks[4];
 	__u8 cache_rumble;
 };