[PATCH 4.9 012/218] iio: inkern: make a best effort on offset calculation

Greg Kroah-Hartman
2022-04-18T14:08:08Z

From: Liam Beguin <liambeguin@gmail.com>

commit ca85123354e1a65a22170286387b4791997fe864 upstream.

iio_convert_raw_to_processed_unlocked() assumes the offset is an
integer. Make a best effort to get a valid offset value for fractional
cases without breaking implicit truncations.

Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220108205319.2046348-4-liambeguin@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/inkern.c | 32 +++++++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 5 deletions(-)

--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -591,13 +591,35 @@ EXPORT_SYMBOL_GPL(iio_read_channel_avera
static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
int raw, int *processed, unsigned int scale)
{
- int scale_type, scale_val, scale_val2, offset;
+ int scale_type, scale_val, scale_val2;
+ int offset_type, offset_val, offset_val2;
s64 raw64 = raw;
- int ret;

- ret = iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_OFFSET);
- if (ret >= 0)
- raw64 += offset;
+ offset_type = iio_channel_read(chan, &offset_val, &offset_val2,
+ IIO_CHAN_INFO_OFFSET);
+ if (offset_type >= 0) {
+ switch (offset_type) {
+ case IIO_VAL_INT:
+ break;
+ case IIO_VAL_INT_PLUS_MICRO:
+ case IIO_VAL_INT_PLUS_NANO:
+ /*
+ * Both IIO_VAL_INT_PLUS_MICRO and IIO_VAL_INT_PLUS_NANO
+ * implicitely truncate the offset to it's integer form.
+ */
+ break;
+ case IIO_VAL_FRACTIONAL:
+ offset_val /= offset_val2;
+ break;
+ case IIO_VAL_FRACTIONAL_LOG2:
+ offset_val >>= offset_val2;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ raw64 += offset_val;
+ }

scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
IIO_CHAN_INFO_SCALE);