Using "end_stage - start_stage" yields "number of used stages -1".
This makes the divisor smaller, hence the dividend greater.

So for example, with 8 (0..7) stages, and max_coord of 1024, the
algo should figure out that 1024 should be split in 8, so 8 slices
of 128. Instead, dividing by 7 will give bigger slices of 146.

While adding these "slices", when stages 7 and 0 are weighted to
determine the abs_pos, a dead-zone appears where we are stuck at
max_coord because of the bigger "slices" and the if that follows:
"if abs_pos > max_coord, then abs_pos = max_coord"

Hence this commit, which re-uses variable "stag_num" initialized with
the number of used stages.

Signed-off-by: Jean-François Dagenais <redacted>
---
drivers/input/misc/ad714x.c |    3 +--
1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/ad714x.c b/drivers/input/misc/ad714x.c
index 2cf26e5..29f5d10 100644
--- a/drivers/input/misc/ad714x.c
+++ b/drivers/input/misc/ad714x.c

@@ -477,8 +477,7 @@ static void ad714x_wheel_cal_abs_pos(struct ad714x_chip *ad714x, int idx)

		ad714x->sensor_val[first_before] +
		ad714x->sensor_val[first_after];

-	sw->abs_pos = ((hw->max_coord / (hw->end_stage - hw->start_stage)) *
-			a_param) / b_param;
+	sw->abs_pos = ((hw->max_coord / stage_num) * a_param) / b_param;

	if (sw->abs_pos > hw->max_coord)
		sw->abs_pos = hw->max_coord;
-- 
1.7.9