[PATCH 2/4] iio: add processed write API

[Romain Gantois <romain.gantois@bootlin.com>]

Add a function to allow IIO consumers to write a processed value to a
channel.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
---
 drivers/iio/inkern.c         | 99 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/iio/consumer.h | 17 ++++++++
 2 files changed, 116 insertions(+)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index c174ebb7d5e6d183674b7ffb15c4ce0f65fa3aed..6486fdb7c66a4c84312541f0f42cc24469972a9c 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -598,6 +598,85 @@ int iio_read_channel_average_raw(struct iio_channel *chan, int *val)
 }
 EXPORT_SYMBOL_GPL(iio_read_channel_average_raw);
 
+static int iio_convert_processed_to_raw_unlocked(struct iio_channel *chan,
+						 int processed, int *raw,
+						 unsigned int scale)
+{
+	int scale_type, scale_val, scale_val2;
+	int offset_type, offset_val, offset_val2;
+	s64 tmp_num, tmp_den;
+
+	scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
+				      IIO_CHAN_INFO_SCALE);
+	if (scale_type >= 0) {
+		switch (scale_type) {
+		case IIO_VAL_INT:
+			tmp_num = processed;
+			tmp_den = scale_val;
+			break;
+		case IIO_VAL_INT_PLUS_MICRO:
+			tmp_num = (s64)processed * 1000000LL;
+
+			if (scale_val2 < 0) {
+				tmp_den = (s64)scale_val * 1000000LL - (s64)scale_val2;
+				tmp_den *= -1;
+			} else {
+				tmp_den = (s64)scale_val * 1000000LL + (s64)scale_val2;
+			}
+
+			break;
+		case IIO_VAL_INT_PLUS_NANO:
+			tmp_num = (s64)processed * 1000000000LL;
+
+			if (scale_val2 < 0) {
+				tmp_den = (s64)scale_val * 1000000000LL - (s64)scale_val2;
+				tmp_den *= -1;
+			} else {
+				tmp_den = (s64)scale_val * 1000000000LL + (s64)scale_val2;
+			}
+
+			break;
+		case IIO_VAL_FRACTIONAL:
+			tmp_num = (s64)processed * (s64)scale_val2;
+			tmp_den = scale_val;
+			break;
+		case IIO_VAL_FRACTIONAL_LOG2:
+			tmp_num = (s64)processed << scale_val2;
+			tmp_den = scale_val;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		tmp_den *= scale;
+
+		*raw = div64_s64(tmp_num, tmp_den);
+	}
+
+	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:
+		case IIO_VAL_INT_PLUS_MICRO:
+		case IIO_VAL_INT_PLUS_NANO:
+			break;
+		case IIO_VAL_FRACTIONAL:
+			offset_val /= offset_val2;
+			break;
+		case IIO_VAL_FRACTIONAL_LOG2:
+			offset_val >>= offset_val2;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		*raw -= offset_val;
+	}
+
+	return 0;
+}
+
 static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 						 int raw, int *processed,
 						 unsigned int scale)
@@ -1028,3 +1107,23 @@ ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf)
 	return do_iio_read_channel_label(chan->indio_dev, chan->channel, buf);
 }
 EXPORT_SYMBOL_GPL(iio_read_channel_label);
+
+int iio_write_channel_processed_scale(struct iio_channel *chan, int val,
+				      unsigned int scale)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev);
+	int ret, processed;
+
+	guard(mutex)(&iio_dev_opaque->info_exist_lock);
+
+	if (!chan->indio_dev->info)
+		return -ENODEV;
+
+	ret = iio_convert_processed_to_raw_unlocked(chan, val, &processed, scale);
+	if (ret)
+		return ret;
+
+	return iio_channel_write(chan, processed, 0, IIO_CHAN_INFO_RAW);
+}
+EXPORT_SYMBOL_GPL(iio_write_channel_processed_scale);
+
diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
index 6a44796164792b2dd930f8168b14de327a80a6f7..79c4804a73b0652d4c16ee5ad07c4543bccd6c92 100644
--- a/include/linux/iio/consumer.h
+++ b/include/linux/iio/consumer.h
@@ -451,4 +451,21 @@ ssize_t iio_write_channel_ext_info(struct iio_channel *chan, const char *attr,
  */
 ssize_t iio_read_channel_label(struct iio_channel *chan, char *buf);
 
+/**
+ * iio_write_channel_processed_scale() - scale and write processed value to a given channel
+ * @chan:		The channel being queried.
+ * @val:		Value to write.
+ * @scale:		Scale factor to apply during the conversion
+ *
+ * Returns an error code or 0.
+ *
+ * This function writes a processed value to a channel. A processed value means
+ * that this value will have the correct unit and not some device internal
+ * representation. If the device does not support writing a processed value, the
+ * function will query the channel's scale and offset and write an appropriately
+ * transformed raw value.
+ */
+int iio_write_channel_processed_scale(struct iio_channel *chan, int val,
+				      unsigned int scale);
+
 #endif

-- 
2.51.0