[PATCH v2 05/19] iio: adc: at91-sama5d2_adc: exit from write_raw() when buffers are enabled

[Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>]

When buffers are enabled conversion may start asynchronously thus
allowing changes on actual hardware could lead to bad behavior. Thus
do not allow changing oversampling ratio and sample frequency when
if iio_device_claim_direct_mode() returns with error.

Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index 2c087d52f164..cd2b8190a8da 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1641,6 +1641,7 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
 			      int val, int val2, long mask)
 {
 	struct at91_adc_state *st = iio_priv(indio_dev);
+	int ret;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
@@ -1650,20 +1651,29 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
 		/* if no change, optimize out */
 		if (val == st->oversampling_ratio)
 			return 0;
+
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
 		mutex_lock(&st->lock);
 		st->oversampling_ratio = val;
 		/* update ratio */
 		at91_adc_config_emr(st);
 		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 		return 0;
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		if (val < st->soc_info.min_sample_rate ||
 		    val > st->soc_info.max_sample_rate)
 			return -EINVAL;
 
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
 		mutex_lock(&st->lock);
 		at91_adc_setup_samp_freq(indio_dev, val);
 		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 		return 0;
 	default:
 		return -EINVAL;
-- 
2.34.1