HID: wiimote: Parse calibration data of balance boards

The raw pressure-data that is reported by balance-boards is pretty useless
unless calibration data is applied. Therefore, we read the full
calibration data on extension initialization and apply it to every
reported data.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Florian Echtler <floe@butterbrot.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 38 insertions, 1 deletions

diff --git a/drivers/hid/hid-wiimote-ext.c b/drivers/hid/hid-wiimote-ext.c
index ae022b863593..fc98cc9ed429 100644
--- a/drivers/hid/hid-wiimote-ext.c
+++ b/drivers/hid/hid-wiimote-ext.c
@@ -28,6 +28,7 @@ struct wiimote_ext {
         bool mp_plugged;
         bool motionp;
         __u8 ext_type;
+        __u16 calib[4][3];
 };
 
 enum wiiext_type {
@@ -127,6 +128,7 @@ error:
 static __u8 ext_read(struct wiimote_ext *ext)
 {
         ssize_t ret;
+        __u8 buf[24], i, j, offs = 0;
         __u8 rmem[2], wmem;
         __u8 type = WIIEXT_NONE;
 
@@ -156,6 +158,26 @@ static __u8 ext_read(struct wiimote_ext *ext)
                         type = WIIEXT_BALANCE_BOARD;
         }
 
+        /* get balance board calibration data */
+        if (type == WIIEXT_BALANCE_BOARD) {
+                ret = wiimote_cmd_read(ext->wdata, 0xa40024, buf, 12);
+                ret += wiimote_cmd_read(ext->wdata, 0xa40024 + 12,
+                                        buf + 12, 12);
+
+                if (ret != 24) {
+                        type = WIIEXT_NONE;
+                } else {
+                        for (i = 0; i < 3; i++) {
+                                for (j = 0; j < 4; j++) {
+                                        ext->calib[j][i] = buf[offs];
+                                        ext->calib[j][i] <<= 8;
+                                        ext->calib[j][i] |= buf[offs + 1];
+                                        offs += 2;
+                                }
+                        }
+                }
+        }
+
         wiimote_cmd_release(ext->wdata);
 
         return type;
@@ -514,7 +536,8 @@ static void handler_classic(struct wiimote_ext *ext, const __u8 *payload)
 
 static void handler_balance_board(struct wiimote_ext *ext, const __u8 *payload)
 {
-        __s32 val[4];
+        __s32 val[4], tmp;
+        unsigned int i;
 
         /*   Byte |  8  7  6  5  4  3  2  1  |
          *   -----+--------------------------+
@@ -553,6 +576,20 @@ static void handler_balance_board(struct wiimote_ext *ext, const __u8 *payload)
         val[3] <<= 8;
         val[3] |= payload[7];
 
+        /* apply calibration data */
+        for (i = 0; i < 4; i++) {
+                if (val[i] < ext->calib[i][1]) {
+                        tmp = val[i] - ext->calib[i][0];
+                        tmp *= 1700;
+                        tmp /= ext->calib[i][1] - ext->calib[i][0];
+                } else {
+                        tmp = val[i] - ext->calib[i][1];
+                        tmp *= 1700;
+                        tmp /= ext->calib[i][2] - ext->calib[i][1] + 1700;
+                }
+                val[i] = tmp;
+        }
+
         input_report_abs(ext->input, ABS_HAT0X, val[0]);
         input_report_abs(ext->input, ABS_HAT0Y, val[1]);
         input_report_abs(ext->input, ABS_HAT1X, val[2]);