iio:inkern: Add function to read the processed value

Add a function to read a processed value from a channel. The function will first
attempt to read the IIO_CHAN_INFO_PROCESSED attribute. If that fails it will
read the IIO_CHAN_INFO_RAW attribute and convert the result from a raw value to
a processed value.

The patch also introduces a function to convert raw value to a processed value
and exports it, in case a user needs or wants to do the conversion by itself.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/inkern.c

@@ -238,9 +238,21 @@ void iio_channel_release_all(struct iio_channel *channels)
 }
 EXPORT_SYMBOL_GPL(iio_channel_release_all);
 
+static int iio_channel_read(struct iio_channel *chan, int *val, int *val2,
+	enum iio_chan_info_enum info)
+{
+	int unused;
+
+	if (val2 == NULL)
+		val2 = &unused;
+
+	return chan->indio_dev->info->read_raw(chan->indio_dev, chan->channel,
+						val, val2, info);
+}
+
 int iio_read_channel_raw(struct iio_channel *chan, int *val)
 {
-	int val2, ret;
+	int ret;
 
 	mutex_lock(&chan->indio_dev->info_exist_lock);
 	if (chan->indio_dev->info == NULL) {
@@ -248,10 +260,7 @@ int iio_read_channel_raw(struct iio_channel *chan, int *val)
 		goto err_unlock;
 	}
 
-	ret = chan->indio_dev->info->read_raw(chan->indio_dev,
-					      chan->channel,
-					      val, &val2,
-					      IIO_CHAN_INFO_RAW);
+	ret = iio_channel_read(chan, val, NULL, IIO_CHAN_INFO_RAW);
 err_unlock:
 	mutex_unlock(&chan->indio_dev->info_exist_lock);
 
@@ -259,6 +268,100 @@ int iio_read_channel_raw(struct iio_channel *chan, int *val)
 }
 EXPORT_SYMBOL_GPL(iio_read_channel_raw);
 
+static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
+	int raw, int *processed, unsigned int scale)
+{
+	int scale_type, scale_val, scale_val2, offset;
+	s64 raw64 = raw;
+	int ret;
+
+	ret = iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_SCALE);
+	if (ret == 0)
+		raw64 += offset;
+
+	scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
+					IIO_CHAN_INFO_SCALE);
+	if (scale_type < 0)
+		return scale_type;
+
+	switch (scale_type) {
+	case IIO_VAL_INT:
+		*processed = raw64 * scale_val;
+		break;
+	case IIO_VAL_INT_PLUS_MICRO:
+		if (scale_val2 < 0)
+			*processed = -raw64 * scale_val;
+		else
+			*processed = raw64 * scale_val;
+		*processed += div_s64(raw64 * (s64)scale_val2 * scale,
+				      1000000LL);
+		break;
+	case IIO_VAL_INT_PLUS_NANO:
+		if (scale_val2 < 0)
+			*processed = -raw64 * scale_val;
+		else
+			*processed = raw64 * scale_val;
+		*processed += div_s64(raw64 * (s64)scale_val2 * scale,
+				      1000000000LL);
+		break;
+	case IIO_VAL_FRACTIONAL:
+		*processed = div_s64(raw64 * (s64)scale_val * scale,
+				     scale_val2);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
+	int *processed, unsigned int scale)
+{
+	int ret;
+
+	mutex_lock(&chan->indio_dev->info_exist_lock);
+	if (chan->indio_dev->info == NULL) {
+		ret = -ENODEV;
+		goto err_unlock;
+	}
+
+	ret = iio_convert_raw_to_processed_unlocked(chan, raw, processed,
+							scale);
+err_unlock:
+	mutex_unlock(&chan->indio_dev->info_exist_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_convert_raw_to_processed);
+
+int iio_read_channel_processed(struct iio_channel *chan, int *val)
+{
+	int ret;
+
+	mutex_lock(&chan->indio_dev->info_exist_lock);
+	if (chan->indio_dev->info == NULL) {
+		ret = -ENODEV;
+		goto err_unlock;
+	}
+
+	if (iio_channel_has_info(chan->channel, IIO_CHAN_INFO_PROCESSED)) {
+		ret = iio_channel_read(chan, val, NULL,
+				       IIO_CHAN_INFO_PROCESSED);
+	} else {
+		ret = iio_channel_read(chan, val, NULL, IIO_CHAN_INFO_RAW);
+		if (ret < 0)
+			goto err_unlock;
+		ret = iio_convert_raw_to_processed_unlocked(chan, *val, val, 1);
+	}
+
+err_unlock:
+	mutex_unlock(&chan->indio_dev->info_exist_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_read_channel_processed);
+
 int iio_read_channel_scale(struct iio_channel *chan, int *val, int *val2)
 {
 	int ret;
@@ -269,10 +372,7 @@ int iio_read_channel_scale(struct iio_channel *chan, int *val, int *val2)
 		goto err_unlock;
 	}
 
-	ret = chan->indio_dev->info->read_raw(chan->indio_dev,
-					      chan->channel,
-					      val, val2,
-					      IIO_CHAN_INFO_SCALE);
+	ret = iio_channel_read(chan, val, val2, IIO_CHAN_INFO_SCALE);
 err_unlock:
 	mutex_unlock(&chan->indio_dev->info_exist_lock);
 

include/linux/iio/consumer.h

@@ -70,6 +70,21 @@ void iio_channel_release_all(struct iio_channel *chan);
 int iio_read_channel_raw(struct iio_channel *chan,
 			 int *val);
 
+/**
+ * iio_read_channel_processed() - read processed value from a given channel
+ * @chan:		The channel being queried.
+ * @val:		Value read back.
+ *
+ * Returns an error code or 0.
+ *
+ * This function will read a processed value from 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 reporting a processed value
+ * the function will query the raw value and the channels scale and offset and
+ * do the appropriate transformation.
+ */
+int iio_read_channel_processed(struct iio_channel *chan, int *val);
+
 /**
  * iio_get_channel_type() - get the type of a channel
  * @channel:		The channel being queried.
@@ -93,4 +108,27 @@ int iio_get_channel_type(struct iio_channel *channel,
 int iio_read_channel_scale(struct iio_channel *chan, int *val,
 			   int *val2);
 
+/**
+ * iio_convert_raw_to_processed() - Converts a raw value to a processed value
+ * @chan:		The channel being queried
+ * @raw:		The raw IIO to convert
+ * @processed:		The result of the conversion
+ * @scale:		Scale factor to apply during the conversion
+ *
+ * Returns an error code or 0.
+ *
+ * This function converts a raw value to processed value for a specific channel.
+ * A raw value is the device internal representation of a sample and the value
+ * returned by iio_read_channel_raw, so the unit of that value is device
+ * depended. A processed value on the other hand is value has a normed unit
+ * according with the IIO specification.
+ *
+ * The scale factor allows to increase the precession of the returned value. For
+ * a scale factor of 1 the function will return the result in the normal IIO
+ * unit for the channel type. E.g. millivolt for voltage channels, if you want
+ * nanovolts instead pass 1000 as the scale factor.
+ */
+int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
+	int *processed, unsigned int scale);
+
 #endif

include/linux/iio/iio.h

@@ -40,6 +40,8 @@ enum iio_chan_info_enum {
 
 #define IIO_CHAN_INFO_SHARED_BIT(type) BIT(type*2)
 #define IIO_CHAN_INFO_SEPARATE_BIT(type) BIT(type*2 + 1)
+#define IIO_CHAN_INFO_BITS(type) (IIO_CHAN_INFO_SHARED_BIT(type) | \
+				    IIO_CHAN_INFO_SEPARATE_BIT(type))
 
 #define IIO_CHAN_INFO_RAW_SEPARATE_BIT			\
 	IIO_CHAN_INFO_SEPARATE_BIT(IIO_CHAN_INFO_RAW)
@@ -261,6 +263,21 @@ struct iio_chan_spec {
 	unsigned		differential:1;
 };
 
+
+/**
+ * iio_channel_has_info() - Checks whether a channel supports a info attribute
+ * @chan: The channel to be queried
+ * @type: Type of the info attribute to be checked
+ *
+ * Returns true if the channels supports reporting values for the given info
+ * attribute type, false otherwise.
+ */
+static inline bool iio_channel_has_info(const struct iio_chan_spec *chan,
+	enum iio_chan_info_enum type)
+{
+	return chan->info_mask & IIO_CHAN_INFO_BITS(type);
+}
+
 #define IIO_ST(si, rb, sb, sh)						\
 	{ .sign = si, .realbits = rb, .storagebits = sb, .shift = sh }