[PATCH v6 06/16] iio: adc: ad4134: Protect conventional device access from debug accesses

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

AD4134 sample read operations may more than one transfer to complete and
are expected to run atomically to avoid triggering any DCLK count error.
Though, register access made from debugfs interface may scramble data if
they are run amidst sample read operations and read/write/modify cycles.

Require debug access to acquire device synchronization locks before
running any transfer requested from debugfs interface.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v5 -> v6:
- Better explanation for requiring debugfs synchronization.

 drivers/iio/adc/ad4134.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iio/adc/ad4134.c b/drivers/iio/adc/ad4134.c
index 1cfa8066f13f..71f626bbe9be 100644
--- a/drivers/iio/adc/ad4134.c
+++ b/drivers/iio/adc/ad4134.c
@@ -302,6 +302,12 @@ static int ad4134_debugfs_reg_access(struct iio_dev *indio_dev,
 {
 	struct ad4134_state *st = iio_priv(indio_dev);
 
+	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
+	if (IIO_DEV_ACQUIRE_FAILED(claim))
+		return -EBUSY;
+
+	guard(mutex)(&st->sync_lock);
+
 	if (readval)
 		return regmap_read(st->regmap, reg, readval);
 
-- 
2.53.0