linux-kernel - [PATCH] staging: iio: tsl2x7x_core: Fix standard deviation calculation

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Message-Id: <1490009225-10268-1-git-send-email-eraretuya@gmail.com>
Date:   Mon, 20 Mar 2017 19:27:05 +0800
From:   Eva Rachel Retuya <eraretuya@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-kernel@...r.kernel.org, abhiram@...utah.edu,
        Eva Rachel Retuya <eraretuya@...il.com>
Subject: [PATCH] staging: iio: tsl2x7x_core: Fix standard deviation calculation

Standard deviation is calculated as the square root of the variance
where variance is the mean of sample_sum and length. Correct the
computation of statP->stddev in accordance to the proper calculation.

Fixes: 3c97c08b5735 ("staging: iio: add TAOS tsl2x7x driver")
Reported-by: Abhiram Balasubramanian <abhiram@...utah.edu>
Signed-off-by: Eva Rachel Retuya <eraretuya@...il.com>
---
 drivers/staging/iio/light/tsl2x7x_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/iio/light/tsl2x7x_core.c b/drivers/staging/iio/light/tsl2x7x_core.c
index ea15bc1..197201a 100644
--- a/drivers/staging/iio/light/tsl2x7x_core.c
+++ b/drivers/staging/iio/light/tsl2x7x_core.c
@@ -854,7 +854,7 @@ void tsl2x7x_prox_calculate(int *data, int length,
 		tmp = data[i] - statP->mean;
 		sample_sum += tmp * tmp;
 	}
-	statP->stddev = int_sqrt((long)sample_sum) / length;
+	statP->stddev = int_sqrt((long)sample_sum / length);
 }
 
 /**
-- 
2.7.4