linux-kernel - [PATCH] iio: adc: ina219: Avoid underflow for sleeping time

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Date:   Wed, 26 Jul 2017 23:32:06 +0200
From:   Stefan Brüns <stefan.bruens@...h-aachen.de>
To:     <linux-iio@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Stefan Brüns <stefan.bruens@...h-aachen.de>
Subject: [PATCH] iio: adc: ina219: Avoid underflow for sleeping time

Proper support for the INA219 lowered the minimum sampling period from
2*140us to 2*84us. Subtracting 200us later leads to an underflow and
an almost infinite udelay later.

Using a signed int for the sampling period provides sufficient range
(at most 2*8640*1024us), but catches the underflow when comparing with
buffer_us.

Fixes: 18edac2e22f4 ("iio: adc: Fix integration time/averaging for INA219/220")
Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
---
 drivers/iio/adc/ina2xx-adc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c
index b0d9e3b80e6d..85b419ea9ba9 100644
--- a/drivers/iio/adc/ina2xx-adc.c
+++ b/drivers/iio/adc/ina2xx-adc.c
@@ -657,7 +657,7 @@ static int ina2xx_capture_thread(void *data)
 {
 	struct iio_dev *indio_dev = data;
 	struct ina2xx_chip_info *chip = iio_priv(indio_dev);
-	unsigned int sampling_us = SAMPLING_PERIOD(chip);
+	int sampling_us = SAMPLING_PERIOD(chip);
 	int buffer_us;
 
 	/*
-- 
2.13.3