linux-kernel - [PATCH] iio: chemical: scd4x: Add pressure compensation

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Date:   Tue,  4 Jul 2023 10:47:06 +0200
From:   Roan van Dijk <roan@...tonic.nl>
To:     jic23@...nel.org
Cc:     lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, roan@...tonic.nl
Subject: [PATCH] iio: chemical: scd4x: Add pressure compensation

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@...tonic.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