[PATCH] iio: ad_sigma_delta: Introduce prepare_channel callback

[Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>]

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

The prepare channel callback will be called before starting a conversion and
can be used by the driver to configure the chip according to the selected
channel.

Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
 drivers/iio/adc/ad_sigma_delta.c       |  5 +++++
 include/linux/iio/adc/ad_sigma_delta.h | 13 +++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index ff5f2da2e1b1..00808838edd8 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -285,6 +285,7 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev,
 		return -EBUSY;
 
 	mutex_lock(&indio_dev->mlock);
+	ad_sigma_delta_prepare_channel(sigma_delta, chan);
 	ad_sigma_delta_set_channel(sigma_delta, chan->address);
 
 	spi_bus_lock(sigma_delta->spi->master);
@@ -351,6 +352,10 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
 
 	channel = find_first_bit(indio_dev->active_scan_mask,
 				 indio_dev->masklength);
+	ret = ad_sigma_delta_prepare_channel(sigma_delta,
+		&indio_dev->channels[channel]);
+	if (ret)
+		goto err_predisable;
 	ret = ad_sigma_delta_set_channel(sigma_delta,
 		indio_dev->channels[channel].address);
 	if (ret)
diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h
index 7e84351fa2c0..21ee12543bdd 100644
--- a/include/linux/iio/adc/ad_sigma_delta.h
+++ b/include/linux/iio/adc/ad_sigma_delta.h
@@ -31,6 +31,8 @@ struct iio_dev;
 
 /**
  * struct ad_sigma_delta_info - Sigma Delta driver specific callbacks and options
+ * @prepare_channel: Will be called to prepare and configure a channel, may be
+ *                   NULL.
  * @set_channel: Will be called to select the current channel, may be NULL.
  * @set_mode: Will be called to select the current mode, may be NULL.
  * @postprocess_sample: Is called for each sampled data word, can be used to
@@ -43,6 +45,8 @@ struct iio_dev;
  *   be used.
  */
 struct ad_sigma_delta_info {
+	int (*prepare_channel)(struct ad_sigma_delta *,
+		const struct iio_chan_spec *);
 	int (*set_channel)(struct ad_sigma_delta *, unsigned int channel);
 	int (*set_mode)(struct ad_sigma_delta *, enum ad_sigma_delta_mode mode);
 	int (*postprocess_sample)(struct ad_sigma_delta *, unsigned int raw_sample);
@@ -81,6 +85,15 @@ struct ad_sigma_delta {
 	uint8_t				data[4] ____cacheline_aligned;
 };
 
+static inline int ad_sigma_delta_prepare_channel(struct ad_sigma_delta *sd,
+	const struct iio_chan_spec *chan)
+{
+	if (sd->info->prepare_channel)
+		return sd->info->prepare_channel(sd, chan);
+
+	return 0;
+}
+
 static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,
 	unsigned int channel)
 {
-- 
2.17.1