--- /dev/null
+/**
+ * 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");
projects / platform / kernel / linux-exynos.git / commitdiff