diff options
Diffstat (limited to 'drivers/iio/humidity/am2315.c')
| -rw-r--r-- | drivers/iio/humidity/am2315.c | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/drivers/iio/humidity/am2315.c b/drivers/iio/humidity/am2315.c new file mode 100644 index 000000000000..d392fc8a9d16 --- /dev/null +++ b/drivers/iio/humidity/am2315.c @@ -0,0 +1,228 @@ +/** + * Aosong AM2315 relative humidity and temperature + * + * Copyright (c) 2016, Intel Corporation. + * + * This file is subject to the terms and conditions of version 2 of + * the GNU General Public License. See the file COPYING in the main + * directory of this archive for more details. + * + * 7-bit I2C address: 0x5C. + */ + +#include <linux/acpi.h> +#include <linux/delay.h> +#include <linux/i2c.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/iio/iio.h> +#include <linux/iio/sysfs.h> + +#define AM2315_REG_HUM_MSB 0x00 +#define AM2315_REG_HUM_LSB 0x01 +#define AM2315_REG_TEMP_MSB 0x02 +#define AM2315_REG_TEMP_LSB 0x03 + +#define AM2315_FUNCTION_READ 0x03 +#define AM2315_HUM_OFFSET 2 +#define AM2315_TEMP_OFFSET 4 + +#define AM2315_DRIVER_NAME "am2315" + +struct am2315_data { + struct i2c_client *client; + struct mutex lock; +}; + +struct am2315_sensor_data { + s16 hum_data; + s16 temp_data; +}; + +static const struct iio_chan_spec am2315_channels[] = { + { + .type = IIO_HUMIDITYRELATIVE, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE) + }, + { + .type = IIO_TEMP, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE) + }, +}; + +/* CRC calculation algorithm, as specified in the datasheet (page 13). */ +static u16 am2315_crc(u8 *data, u8 nr_bytes) +{ + int i; + u16 crc = 0xffff; + + while (nr_bytes--) { + crc ^= *data++; + for (i = 0; i < 8; i++) { + if (crc & 0x01) { + crc >>= 1; + crc ^= 0xA001; + } else { + crc >>= 1; + } + } + } + + return crc; +} + +/* Simple function that sends a few bytes to the device to wake it up. */ +static void am2315_ping(struct i2c_client *client) +{ + i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB); +} + +static int am2315_read_data(struct am2315_data *data, + struct am2315_sensor_data *sensor_data) +{ + int ret; + /* tx_buf format: <function code> <start addr> <nr of regs to read> */ + u8 tx_buf[3] = { AM2315_FUNCTION_READ, AM2315_REG_HUM_MSB, 4 }; + /* + * rx_buf format: + * <function code> <number of registers read> + * <humidity MSB> <humidity LSB> <temp MSB> <temp LSB> + * <CRC LSB> <CRC MSB> + */ + u8 rx_buf[8]; + u16 crc; + + /* First wake up the device. */ + am2315_ping(data->client); + + mutex_lock(&data->lock); + ret = i2c_master_send(data->client, tx_buf, sizeof(tx_buf)); + if (ret < 0) { + dev_err(&data->client->dev, "failed to send read request\n"); + goto exit_unlock; + } + /* Wait 2-3 ms, then read back the data sent by the device. */ + usleep_range(2000, 3000); + /* Do a bulk data read, then pick out what we need. */ + ret = i2c_master_recv(data->client, rx_buf, sizeof(rx_buf)); + if (ret < 0) { + dev_err(&data->client->dev, "failed to read sensor data\n"); + goto exit_unlock; + } + mutex_unlock(&data->lock); + /* + * Do a CRC check on the data and compare it to the value + * calculated by the device. + */ + crc = am2315_crc(rx_buf, sizeof(rx_buf) - 2); + if ((crc & 0xff) != rx_buf[6] || (crc >> 8) != rx_buf[7]) { + dev_err(&data->client->dev, "failed to verify sensor data\n"); + return -EIO; + } + + sensor_data->hum_data = (rx_buf[AM2315_HUM_OFFSET] << 8) | + rx_buf[AM2315_HUM_OFFSET + 1]; + sensor_data->temp_data = (rx_buf[AM2315_TEMP_OFFSET] << 8) | + rx_buf[AM2315_TEMP_OFFSET + 1]; + + return ret; + +exit_unlock: + mutex_unlock(&data->lock); + return ret; +} + +static int am2315_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, + int *val, int *val2, long mask) +{ + int ret; + struct am2315_sensor_data sensor_data; + struct am2315_data *data = iio_priv(indio_dev); + + switch (mask) { + case IIO_CHAN_INFO_RAW: + ret = am2315_read_data(data, &sensor_data); + if (ret < 0) + return ret; + *val = (chan->type == IIO_HUMIDITYRELATIVE) ? + sensor_data.hum_data : sensor_data.temp_data; + return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: + *val = 100; + return IIO_VAL_INT; + } + + return -EINVAL; +} + +static const struct iio_info am2315_info = { + .driver_module = THIS_MODULE, + .read_raw = am2315_read_raw, +}; + +static int am2315_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct iio_dev *indio_dev; + struct am2315_data *data; + + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); + if (!indio_dev) { + dev_err(&client->dev, "iio allocation failed!\n"); + return -ENOMEM; + } + + data = iio_priv(indio_dev); + data->client = client; + i2c_set_clientdata(client, indio_dev); + mutex_init(&data->lock); + + indio_dev->dev.parent = &client->dev; + indio_dev->info = &am2315_info; + indio_dev->name = AM2315_DRIVER_NAME; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->channels = am2315_channels; + indio_dev->num_channels = ARRAY_SIZE(am2315_channels); + + return iio_device_register(indio_dev); +} + +static int am2315_remove(struct i2c_client *client) +{ + struct iio_dev *indio_dev = i2c_get_clientdata(client); + + iio_device_unregister(indio_dev); + + return 0; +} + +static const struct i2c_device_id am2315_i2c_id[] = { + {"am2315", 0}, + {} +}; + +static const struct acpi_device_id am2315_acpi_id[] = { + {"AOS2315", 0}, + {} +}; + +MODULE_DEVICE_TABLE(acpi, am2315_acpi_id); + +static struct i2c_driver am2315_driver = { + .driver = { + .name = "am2315", + .acpi_match_table = ACPI_PTR(am2315_acpi_id), + }, + .probe = am2315_probe, + .remove = am2315_remove, + .id_table = am2315_i2c_id, +}; + +module_i2c_driver(am2315_driver); + +MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>"); +MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature"); +MODULE_LICENSE("GPL v2"); |