[PATCH 2/3] iio: pressure: Add driver for Sensirion SDP500

[Petar Stoykov]

Sensirion SDP500 is a digital differential pressure sensor. The sensor is
accessed over I2C.

Signed-off-by: Petar Stoykov <pd.pstoykov@xxxxxxxxx>
---
 drivers/iio/pressure/Kconfig  |   9 ++
 drivers/iio/pressure/Makefile |   1 +
 drivers/iio/pressure/sdp500.c | 201 ++++++++++++++++++++++++++++++++++
 3 files changed, 211 insertions(+)
 create mode 100644 drivers/iio/pressure/sdp500.c

diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index 95efa32e4289..5debdfbd5324 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -212,6 +212,15 @@ config MS5637
       This driver can also be built as a module. If so, the module will
       be called ms5637.

+config SDP500
+    tristate "Sensirion SDP500 differential pressure sensor I2C driver"
+    depends on I2C
+    help
+      Say Y here to build support for Sensirion SDP500 differential pressure
+      sensor I2C driver.
+      To compile this driver as a module, choose M here: the core module
+      will be called sdp500.
+
 config IIO_ST_PRESS
     tristate "STMicroelectronics pressure sensor Driver"
     depends on (I2C || SPI_MASTER) && SYSFS
diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
index 436aec7e65f3..489ef7b7befa 100644
--- a/drivers/iio/pressure/Makefile
+++ b/drivers/iio/pressure/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_MS5611) += ms5611_core.o
 obj-$(CONFIG_MS5611_I2C) += ms5611_i2c.o
 obj-$(CONFIG_MS5611_SPI) += ms5611_spi.o
 obj-$(CONFIG_MS5637) += ms5637.o
+obj-$(CONFIG_SDP500) += sdp500.o
 obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
 st_pressure-y := st_pressure_core.o
 st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
diff --git a/drivers/iio/pressure/sdp500.c b/drivers/iio/pressure/sdp500.c
new file mode 100644
index 000000000000..bc492ef3ef3e
--- /dev/null
+++ b/drivers/iio/pressure/sdp500.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+
+#define SDP500_CRC8_POLYNOMIAL  0x31   // x8 + x5 + x4 + 1 (normalized to 0x31)
+#define SDP500_READ_SIZE        3
+
+#define SDP500_SCALE_FACTOR 60
+
+#define SDP500_I2C_START_MEAS 0xF1
+
+#define sdp500_err(idev, fmt, ...)                    \
+    dev_err(idev->dev.parent, fmt "\n", ##__VA_ARGS__)
+
+#define sdp500_dbg(idev, fmt, ...)                    \
+    dev_dbg(idev->dev.parent, fmt "\n", ##__VA_ARGS__)
+
+#define sdp500_info(idev, fmt, ...)                    \
+    dev_info(idev->dev.parent, fmt "\n", ##__VA_ARGS__)
+
+struct sdp500_data {
+    struct device *dev;
+};
+
+uint8_t calculate_crc8(uint8_t *data, uint32_t len, uint8_t poly)
+{
+    uint8_t    count = 0;
+    uint8_t    value = 0;
+    uint8_t    temp = 0;
+
+    while (len--) {
+        temp = *(data);
+        data++;
+        value ^= temp;
+        for (count = 0; count < BITS_PER_BYTE; count++) {
+            if (value & 0x80)
+                value = (value << 1) ^ poly;
+            else
+                value = value << 1;
+        }
+    }
+
+    return value;
+}
+
+static int sdp500_xfer(struct sdp500_data *data, u8 *txbuf, size_t txsize,
+              u8 *rxbuf, size_t rxsize, const struct iio_dev *indio_dev)
+{
+    struct i2c_client *client = to_i2c_client(data->dev);
+    int ret;
+
+    ret = i2c_master_send(client, txbuf, txsize);
+    if (ret < 0) {
+        sdp500_err(indio_dev, "Failed to send data");
+        return ret;
+    }
+    if (ret != txsize) {
+        sdp500_err(indio_dev, "Data is sent wrongly");
+        return -EIO;
+    }
+
+    if (!rxsize)
+        return 0;
+
+    ret = i2c_master_recv(client, rxbuf, rxsize);
+    if (ret < 0) {
+        sdp500_err(indio_dev, "Failed to receive data");
+        return ret;
+    }
+    if (ret != rxsize) {
+        sdp500_err(indio_dev, "Data is received wrongly");
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static int sdp500_start_measurement(struct sdp500_data *data, const
struct iio_dev *indio_dev)
+{
+    u8 txbuf = SDP500_I2C_START_MEAS;
+
+    return sdp500_xfer(data, &txbuf, 1, NULL, 0, indio_dev);
+}
+
+static const struct iio_chan_spec sdp500_channels[] = {
+    {
+        .type = IIO_PRESSURE,
+        .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+    },
+};
+
+static int sdp500_read_raw(struct iio_dev *indio_dev,
+              struct iio_chan_spec const *chan,
+              int *val, int *val2, long mask)
+{
+    int ret = -EINVAL;
+    u8 rxbuf[SDP500_READ_SIZE];
+    u8 rec_crc, calculated_crc;
+    s16 dec_value;
+    struct sdp500_data *data = iio_priv(indio_dev);
+
+    switch (mask) {
+    case IIO_CHAN_INFO_PROCESSED:
+        sdp500_xfer(data, NULL, 0, rxbuf, SDP500_READ_SIZE, indio_dev);
+        rec_crc = rxbuf[2];
+        calculated_crc = calculate_crc8(rxbuf, SDP500_READ_SIZE - 1,
+                        SDP500_CRC8_POLYNOMIAL);
+        if (rec_crc != calculated_crc) {
+            sdp500_err(indio_dev, "calculated crc = 0x%.2X but
received 0x%.2X",
+                calculated_crc, rec_crc);
+            return -EIO;
+        }
+
+        dec_value = ((rxbuf[0] << 8) & 0xFF00) | rxbuf[1];
+        sdp500_dbg(indio_dev, "dec value = %d", dec_value);
+
+        *val = dec_value;
+        *val2 = SDP500_SCALE_FACTOR;
+        ret = IIO_VAL_FRACTIONAL;
+        break;
+    }
+    return ret;
+}
+
+static const struct iio_info sdp500_info = {
+    .read_raw = &sdp500_read_raw,
+};
+
+static int sdp500_probe(struct i2c_client *client)
+{
+    struct iio_dev *indio_dev;
+    struct sdp500_data *data;
+    struct device *dev = &client->dev;
+    int ret;
+
+    indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+    if (!indio_dev) {
+        dev_err(dev->parent, "Failed to allocate iio device\n");
+        return -ENOMEM;
+    }
+
+    i2c_set_clientdata(client, indio_dev);
+
+    data = iio_priv(indio_dev);
+    data->dev = dev;
+
+    indio_dev->dev.parent = dev;
+    indio_dev->name = client->name;
+    indio_dev->channels = sdp500_channels;
+    indio_dev->info = &sdp500_info;
+    indio_dev->modes = INDIO_DIRECT_MODE;
+    indio_dev->num_channels = ARRAY_SIZE(sdp500_channels);
+
+    ret = sdp500_start_measurement(data, indio_dev);
+    if (ret) {
+        sdp500_err(indio_dev, "Failed to start measurement");
+        return ret;
+    }
+
+    ret = iio_device_register(indio_dev);
+    if (ret < 0) {
+        sdp500_err(indio_dev, "Failed to register indio_dev");
+        return ret;
+    }
+
+    return 0;
+}
+
+static const struct i2c_device_id sdp500_id[] = {
+    { "sdp500" },
+    { },
+};
+MODULE_DEVICE_TABLE(i2c, sdp500_id);
+
+static void sdp500_remove(struct i2c_client *client)
+{
+    struct iio_dev *indio_dev = dev_get_drvdata(&client->dev);
+
+    iio_device_unregister(indio_dev);
+}
+
+static const struct of_device_id sdp500_of_match[] = {
+    { .compatible = "sensirion,sdp500" },
+    { }
+};
+MODULE_DEVICE_TABLE(of, sdp500_of_match);
+
+static struct i2c_driver sdp500_driver = {
+    .driver = {
+        .name    = "sensirion,sdp500",
+        .of_match_table = sdp500_of_match,
+    },
+    .probe        = sdp500_probe,
+    .remove        = sdp500_remove,
+    .id_table    = sdp500_id,
+};
+module_i2c_driver(sdp500_driver);
+
+MODULE_AUTHOR("Thomas Sioutas <thomas.sioutas@xxxxxxxxxxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Driver for Sensirion SDP500 differential pressure sensor");
+MODULE_LICENSE("GPL");
-- 
2.30.2