[PATCH] iio: chemical: scd4x: Add pressure compensation

[Roan van Dijk <roan@protonic.nl>]

This patch adds pressure compensation to the scd4x driver. The pressure can
be written to the sensor in hPa. The pressure will be compensated
internally by the sensor.

Signed-off-by: Roan van Dijk <roan@protonic.nl>
---
 drivers/iio/chemical/scd4x.c | 41 +++++++++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
index a4f22d926400..fe6b3f3f7186 100644
--- a/drivers/iio/chemical/scd4x.c
+++ b/drivers/iio/chemical/scd4x.c
@@ -36,6 +36,8 @@
 #define SCD4X_WRITE_BUF_SIZE 5
 #define SCD4X_FRC_MIN_PPM 0
 #define SCD4X_FRC_MAX_PPM 2000
+#define SCD4X_AMB_PRESSURE_MIN 700
+#define SCD4X_AMB_PRESSURE_MAX 1200
 #define SCD4X_READY_MASK 0x01
 
 /*Commands SCD4X*/
@@ -45,6 +47,8 @@ enum scd4x_cmd {
 	CMD_STOP_MEAS           = 0x3f86,
 	CMD_SET_TEMP_OFFSET     = 0x241d,
 	CMD_GET_TEMP_OFFSET     = 0x2318,
+	CMD_SET_AMB_PRESSURE	= 0xe000,
+	CMD_GET_AMB_PRESSURE	= 0xe000,
 	CMD_FRC                 = 0x362f,
 	CMD_SET_ASC             = 0x2416,
 	CMD_GET_ASC             = 0x2313,
@@ -373,7 +377,10 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_CALIBBIAS:
 		mutex_lock(&state->lock);
-		ret = scd4x_read(state, CMD_GET_TEMP_OFFSET, &tmp, sizeof(tmp));
+		if (chan->type == IIO_TEMP)
+			ret = scd4x_read(state, CMD_GET_TEMP_OFFSET, &tmp, sizeof(tmp));
+		else if (chan->type == IIO_PRESSURE)
+			ret = scd4x_read(state, CMD_GET_AMB_PRESSURE, &tmp, sizeof(tmp));
 		mutex_unlock(&state->lock);
 		if (ret)
 			return ret;
@@ -386,6 +393,25 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static const int scd4x_pressure_calibbias_available[] = {
+	SCD4X_AMB_PRESSURE_MIN, 1, SCD4X_AMB_PRESSURE_MAX,
+};
+
+static int scd4x_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			    const int **vals, int *type, int *length, long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_CALIBBIAS:
+		*vals = scd4x_pressure_calibbias_available;
+		*type = IIO_VAL_INT;
+
+		return IIO_AVAIL_RANGE;
+	}
+
+	return -EINVAL;
+}
+
+
 static int scd4x_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
 				int val, int val2, long mask)
 {
@@ -395,9 +421,11 @@ static int scd4x_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const
 	switch (mask) {
 	case IIO_CHAN_INFO_CALIBBIAS:
 		mutex_lock(&state->lock);
-		ret = scd4x_write(state, CMD_SET_TEMP_OFFSET, val);
+		if (chan->type == IIO_TEMP)
+			ret = scd4x_write(state, CMD_SET_TEMP_OFFSET, val);
+		else if (chan->type == IIO_PRESSURE)
+			ret = scd4x_write(state, CMD_SET_AMB_PRESSURE, val);
 		mutex_unlock(&state->lock);
-
 		return ret;
 	default:
 		return -EINVAL;
@@ -503,9 +531,16 @@ static const struct iio_info scd4x_info = {
 	.attrs = &scd4x_attr_group,
 	.read_raw = scd4x_read_raw,
 	.write_raw = scd4x_write_raw,
+	.read_avail = scd4x_read_avail,
 };
 
 static const struct iio_chan_spec scd4x_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBBIAS),
+		.info_mask_separate_available = BIT(IIO_CHAN_INFO_CALIBBIAS),
+		.scan_index = -1,
+	},
 	{
 		.type = IIO_CONCENTRATION,
 		.channel2 = IIO_MOD_CO2,
-- 
2.39.2