[PATCH v6 02/10] iio: adc: ad7124: Refuse invalid input specifiers

Uwe Kleine-König
2024-12-06T17:29:15Z

The ad7124-4 has 8 analog inputs; the input select values 8 to 15 are
reserved and not to be used. These are fine for ad7124-8. For both
ad7124-4 and ad7124-8 values bigger than 15 are internal channels that
might appear as inputs in the channels specified in the device
description according to the description of commit f1794fd7bdf7 ("iio:
adc: ad7124: Remove input number limitation"), values bigger than 31
don't fit into the respective register bit field and the driver masked
them to smaller values.

Check for these invalid input specifiers and fail to probe if one is
found.

Fixes: f1794fd7bdf7 ("iio: adc: ad7124: Remove input number limitation")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
---
drivers/iio/adc/ad7124.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 5352b26bb391..1f3342373f1c 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -807,6 +807,19 @@ static int ad7124_check_chip_id(struct ad7124_state *st)
return 0;
}

+/*
+ * Input specifiers 8 - 15 are explicitly reserved for ad7124-4
+ * while they are fine for ad7124-8. Values above 31 don't fit
+ * into the register field and so are invalid for sure.
+ */
+static bool ad7124_valid_input_select(unsigned int ain, const struct ad7124_chip_info *info)
+{
+ if (ain >= info->num_inputs && ain < 16)
+ return false;
+
+ return ain <= FIELD_MAX(AD7124_CHANNEL_AINM_MSK);
+}
+
static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
struct device *dev)
{
@@ -859,6 +872,11 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
if (ret)
return ret;

+ if (!ad7124_valid_input_select(ain[0], st->chip_info) ||
+ !ad7124_valid_input_select(ain[1], st->chip_info))
+ return dev_err_probe(dev, -EINVAL,
+ "diff-channels property of %pfwP contains invalid data\n", child);
+
st->channels[channel].nr = channel;
st->channels[channel].ain = AD7124_CHANNEL_AINP(ain[0]) |
AD7124_CHANNEL_AINM(ain[1]);
--
2.45.2