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Subject[PATCH v2 4/4] staging: iio: adt7316: fix the dac write calculation
Date
The lsb calculation is not masking the correct bits from the user input.
Subtract 1 from (1 << offset) to correctly set up the mask to be applied
to user input.

The lsb register stores its value starting at the bit 7 position.
adt7316_store_DAC() currently assumes the value is at the other end of the
register. Shift the lsb value before storing it in a new variable lsb_reg,
and write this variable to the lsb register.

Fixes: 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")
Signed-off-by: Jeremy Fertic <jeremyfertic@gmail.com>
---
drivers/staging/iio/addac/adt7316.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/iio/addac/adt7316.c b/drivers/staging/iio/addac/adt7316.c
index d7f3d68e525b..6f7891b567b9 100644
--- a/drivers/staging/iio/addac/adt7316.c
+++ b/drivers/staging/iio/addac/adt7316.c
@@ -1431,7 +1431,7 @@ static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
static ssize_t adt7316_store_DAC(struct adt7316_chip_info *chip,
int channel, const char *buf, size_t len)
{
- u8 msb, lsb, offset;
+ u8 msb, lsb, lsb_reg, offset;
u16 data;
int ret;

@@ -1449,9 +1449,13 @@ static ssize_t adt7316_store_DAC(struct adt7316_chip_info *chip,
return -EINVAL;

if (chip->dac_bits > 8) {
- lsb = data & (1 << offset);
+ lsb = data & ((1 << offset) - 1);
+ if (chip->dac_bits == 12)
+ lsb_reg = lsb << ADT7316_DA_12_BIT_LSB_SHIFT;
+ else
+ lsb_reg = lsb << ADT7316_DA_10_BIT_LSB_SHIFT;
ret = chip->bus.write(chip->bus.client,
- ADT7316_DA_DATA_BASE + channel * 2, lsb);
+ ADT7316_DA_DATA_BASE + channel * 2, lsb_reg);
if (ret)
return -EIO;
}
--
2.19.1
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