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iio: dac: ad5758: Fix the offset calculation

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The offset is a count of DAC codes, so the microamp or microvolt units
of min and max cancel out and the final division by 1000 is wrong. For
the +-20 mA range the driver reports -32 instead of -32768. For the
+-5 V and +-10 V ranges min * (1 << 16) also overflows int, and the
reported offset is 0.

Drop the division and do the multiplication in 64 bits.

Fixes: 28d1a7ac2a ("iio: dac: Add AD5758 support")
Signed-off-by: Arka Mondal <arka@arkamondal.net>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
This commit is contained in:
Arka Mondal 2026-09-18 21:20:30 +09:00 committed by Jonathan Cameron
parent ebc026be1b
commit a3b3580713
1 changed files with 2 additions and 1 deletions
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3
drivers/iio/dac/ad5758.c
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@ -9,6 +9,7 @@
#include <linux/bsearch.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/spi/spi.h>
@ -540,7 +541,7 @@ static int ad5758_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_OFFSET:
min = st->out_range.min;
max = st->out_range.max;
*val = ((min * (1 << 16)) / (max - min)) / 1000;
*val = div_s64((s64)min * (1 << 16), max - min);
return IIO_VAL_INT;
default:
return -EINVAL;