iio:adc:ad799x: Fix reading and writing of event values, apply shift

last two bits of ADC and limit values are zero and should not be reported
(ad7993, ad7997); compare with read_raw()

event values are 10 (ad7993, ad7997) or 12 bit max., check the range on write

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Stable@vger.kernel.org
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 39b4cb48d738..6eba301ee03d 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -427,9 +427,12 @@ static int ad799x_write_event_value(struct iio_dev *indio_dev,
         int ret;
         struct ad799x_state *st = iio_priv(indio_dev);
 
+        if (val < 0 || val > RES_MASK(chan->scan_type.realbits))
+                return -EINVAL;
+
         mutex_lock(&indio_dev->mlock);
         ret = ad799x_i2c_write16(st, ad799x_threshold_reg(chan, dir, info),
-                val);
+                val << chan->scan_type.shift);
         mutex_unlock(&indio_dev->mlock);
 
         return ret;
@@ -452,7 +455,8 @@ static int ad799x_read_event_value(struct iio_dev *indio_dev,
         mutex_unlock(&indio_dev->mlock);
         if (ret < 0)
                 return ret;
-        *val = valin;
+        *val = (valin >> chan->scan_type.shift) &
+                RES_MASK(chan->scan_type.realbits);
 
         return IIO_VAL_INT;
 }