[PATCH v2] iio: accel: Add driver for the Analog Devices ADXL345 3-axis accelerometer

[Eva Rachel Retuya]

Add basic IIO support for the Analog Devices ADXL345 3-axis accelerometer.
The datasheet can be found here:
http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf

Signed-off-by: Eva Rachel Retuya <eraretuya@xxxxxxxxx>
Cc: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
Cc: Daniel Baluta <daniel.baluta@xxxxxxxxx>
Cc: Alison Schofield <amsfield22@xxxxxxxxx>
---
v1 Mailing list discussion:
https://marc.info/?l=linux-iio&m=148533644407371&w=2 

Changes since v1:
* Switch tag from RFC to PATCH
>From Jonathan's Review
* Kconfig: add input driver's (adxl34x) selection state as dependency.
>From Peter's Review
* Implement full-resolution mode scale.
* Add comment stating FULL_RES is up to 13-bits in resolution.
* Drop newline and le16_to_cpu usage in read_raw.
* Allow the sensor to return to standby mode if iio_device_register fails.

 drivers/iio/accel/Kconfig   |  11 +++
 drivers/iio/accel/Makefile  |   1 +
 drivers/iio/accel/adxl345.c | 194 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 206 insertions(+)
 create mode 100644 drivers/iio/accel/adxl345.c

diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index ef8401a..2308bac 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -5,6 +5,17 @@
 
 menu "Accelerometers"
 
+config ADXL345
+	tristate "Analog Devices ADXL345 3-Axis Digital Accelerometer Driver"
+	depends on !(INPUT_ADXL34X=y || INPUT_ADXL34X=m)
+	depends on I2C
+	help
+	  Say Y here if you want to build support for the Analog Devices
+	  ADXL345 3-axis digital accelerometer.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called adxl345.
+
 config BMA180
 	tristate "Bosch BMA180/BMA250 3-Axis Accelerometer Driver"
 	depends on I2C
diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
index 69fe8ed..618488d 100644
--- a/drivers/iio/accel/Makefile
+++ b/drivers/iio/accel/Makefile
@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_ADXL345) += adxl345.o
 obj-$(CONFIG_BMA180) += bma180.o
 obj-$(CONFIG_BMA220) += bma220_spi.o
 obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o
diff --git a/drivers/iio/accel/adxl345.c b/drivers/iio/accel/adxl345.c
new file mode 100644
index 0000000..c34991f
--- /dev/null
+++ b/drivers/iio/accel/adxl345.c
@@ -0,0 +1,194 @@
+/*
+ * ADXL345 3-Axis Digital Accelerometer
+ *
+ * Copyright (c) 2017 Eva Rachel Retuya <eraretuya@xxxxxxxxx>
+ *
+ * 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.
+ *
+ * IIO driver for ADXL345
+ * 7-bit I2C slave address: 0x1D (ALT ADDRESS pin tied to VDDIO) or
+ * 0x53 (ALT ADDRESS pin grounded)
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+
+#define ADXL345_REG_DEVID		0x00
+#define ADXL345_REG_POWER_CTL		0x2D
+#define ADXL345_REG_DATA_FORMAT		0x31
+#define ADXL345_REG_DATAX0		0x32
+#define ADXL345_REG_DATAY0		0x34
+#define ADXL345_REG_DATAZ0		0x36
+
+#define ADXL345_POWER_CTL_MEASURE	BIT(3)
+#define ADXL345_POWER_CTL_STANDBY	0x00
+
+#define ADXL345_DATA_FORMAT_FULL_RES	BIT(3) /* Up to 13-bits resolution */
+#define ADXL345_DATA_FORMAT_2G		0
+#define ADXL345_DATA_FORMAT_4G		1
+#define ADXL345_DATA_FORMAT_8G		2
+#define ADXL345_DATA_FORMAT_16G		3
+
+#define ADXL345_DEVID			0xE5
+
+/*
+ * In full-resolution mode, scale factor is maintained at ~4 mg/LSB
+ * in all g ranges.
+ *
+ * At +/- 16g with 13-bit resolution, scale is computed as:
+ * (16 + 16) * 9.81 / (2^13 - 1) = 0.0383
+ */
+static const int adxl345_uscale = 38300;
+
+struct adxl345_data {
+	struct i2c_client *client;
+	u8 data_range;
+};
+
+#define ADXL345_CHANNEL(reg, axis) {					\
+	.type = IIO_ACCEL,						\
+	.modified = 1,							\
+	.channel2 = IIO_MOD_##axis,					\
+	.address = reg,							\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+}
+
+static const struct iio_chan_spec adxl345_channels[] = {
+	ADXL345_CHANNEL(ADXL345_REG_DATAX0, X),
+	ADXL345_CHANNEL(ADXL345_REG_DATAY0, Y),
+	ADXL345_CHANNEL(ADXL345_REG_DATAZ0, Z),
+};
+
+static int adxl345_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct adxl345_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		/*
+		 * Data is stored in adjacent registers:
+		 * ADXL345_REG_DATA(X0/Y0/Z0) contain the least significant byte
+		 * and ADXL345_REG_DATA(X0/Y0/Z0) + 1 the most significant byte
+		 */
+		ret = i2c_smbus_read_word_data(data->client, chan->address);
+		if (ret < 0)
+			return ret;
+
+		*val = sign_extend32(ret, 12);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = adxl345_uscale;
+
+		return IIO_VAL_INT_PLUS_MICRO;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info adxl345_info = {
+	.driver_module	= THIS_MODULE,
+	.read_raw	= adxl345_read_raw,
+};
+
+static int adxl345_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct adxl345_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(client, ADXL345_REG_DEVID);
+	if (ret < 0) {
+		dev_err(&client->dev, "Error reading device ID: %d\n", ret);
+		return ret;
+	}
+
+	if (ret != ADXL345_DEVID) {
+		dev_err(&client->dev, "Invalid device ID: %d\n", ret);
+		return -ENODEV;
+	}
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	/* Enable full-resolution mode */
+	data->data_range = ADXL345_DATA_FORMAT_FULL_RES;
+
+	ret = i2c_smbus_write_byte_data(data->client, ADXL345_REG_DATA_FORMAT,
+					data->data_range);
+	if (ret < 0) {
+		dev_err(&client->dev, "Failed to set data range: %d\n", ret);
+		return ret;
+	}
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = id->name;
+	indio_dev->info = &adxl345_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = adxl345_channels;
+	indio_dev->num_channels = ARRAY_SIZE(adxl345_channels);
+
+	/* Enable measurement mode */
+	ret = i2c_smbus_write_byte_data(data->client, ADXL345_REG_POWER_CTL,
+					ADXL345_POWER_CTL_MEASURE);
+	if (ret < 0) {
+		dev_err(&client->dev, "Failed to enable measurement mode: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0) {
+		dev_err(&client->dev, "iio_device_register failed: %d\n", ret);
+		i2c_smbus_write_byte_data(data->client, ADXL345_REG_POWER_CTL,
+					  ADXL345_POWER_CTL_STANDBY);
+	}
+
+	return ret;
+}
+
+static int adxl345_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct adxl345_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	return i2c_smbus_write_byte_data(data->client, ADXL345_REG_POWER_CTL,
+					 ADXL345_POWER_CTL_STANDBY);
+}
+
+static const struct i2c_device_id adxl345_i2c_id[] = {
+	{ "adxl345", 0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, adxl345_i2c_id);
+
+static struct i2c_driver adxl345_driver = {
+	.driver = {
+		.name	= "adxl345",
+	},
+	.probe		= adxl345_probe,
+	.remove		= adxl345_remove,
+	.id_table	= adxl345_i2c_id,
+};
+
+module_i2c_driver(adxl345_driver);
+
+MODULE_AUTHOR("Eva Rachel Retuya <eraretuya@xxxxxxxxx>");
+MODULE_DESCRIPTION("ADXL345 3-Axis Digital Accelerometer driver");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4