[PATCH v2] iio: accel: add support for Memsic MXC6255XC sensor

[PATCH v2] iio: accel: add support for Memsic MXC6255XC sensor

[Teodora Baluta]

This patch adds a minimal implementation for the Memsic MXC6255XC
orientation sensing accelerometer. The supported operations are reading
raw acceleration values for X/Y axis that can be scaled using the
exposed scale.

Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
---
Changes since v1:

- remove scale_available attribute
- use chan->address instead
- drop _AXIS_TO_REG macro
- put register address in .address field of MXC6255_CHANNEL macro
- check chip id
- use "as follows" instead of "as following"

 drivers/iio/accel/Kconfig   |  11 +++
 drivers/iio/accel/Makefile  |   1 +
 drivers/iio/accel/mxc6255.c | 199 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 211 insertions(+)
 create mode 100644 drivers/iio/accel/mxc6255.c

diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index 969428d..75ac087 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -158,6 +158,17 @@ config MXC4005
 	  To compile this driver as a module, choose M. The module will be
 	  called mxc4005.
 
+config MXC6255
+	tristate "Memsic MXC6255 Orientation Sensing Accelerometer Driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say yes here to build support for the Memsic MXC6255 Orientation
+	  Sensing Accelerometer Driver.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called mxc6255.
+
 config STK8312
 	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
 	depends on I2C
diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
index 7925f16..525ed52 100644
--- a/drivers/iio/accel/Makefile
+++ b/drivers/iio/accel/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_MMA9551)		+= mma9551.o
 obj-$(CONFIG_MMA9553)		+= mma9553.o
 
 obj-$(CONFIG_MXC4005)		+= mxc4005.o
+obj-$(CONFIG_MXC6255)		+= mxc6255.o
 
 obj-$(CONFIG_STK8312)		+= stk8312.o
 obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
diff --git a/drivers/iio/accel/mxc6255.c b/drivers/iio/accel/mxc6255.c
new file mode 100644
index 0000000..b853ff0
--- /dev/null
+++ b/drivers/iio/accel/mxc6255.c
@@ -0,0 +1,199 @@
+/*
+ * MXC6255 - MEMSIC orientation sensing accelerometer
+ *
+ * Copyright (c) 2015, 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.
+ *
+ * IIO driver for MXC6255 (7-bit I2C slave address 0x15).
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/iio/iio.h>
+#include <linux/delay.h>
+#include <linux/acpi.h>
+#include <linux/regmap.h>
+#include <linux/iio/sysfs.h>
+
+#define MXC6255_DRV_NAME		"mxc6255"
+#define MXC6255_REGMAP_NAME		"mxc6255_regmap"
+
+#define MXC6255_REG_XOUT		0x00
+#define MXC6255_REG_YOUT		0x01
+#define MXC6255_REG_CHIP_ID		0x08
+
+#define MXC6255_CHIP_ID			0x05
+
+/*
+ * MXC6255 has only one measurement range: +/- 2G.
+ * The acceleration output is an 8-bit value.
+ *
+ * Scale is calculated as follows:
+ * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
+ *
+ * Scale value for +/- 2G measurement range
+ */
+#define MXC6255_SCALE			153829
+
+enum mxc6255_axis {
+	AXIS_X,
+	AXIS_Y,
+};
+
+struct mxc6255_data {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+static int mxc6255_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct mxc6255_data *data = iio_priv(indio_dev);
+	unsigned int reg;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = regmap_read(data->regmap, chan->address, &reg);
+		if (ret < 0) {
+			dev_err(&data->client->dev,
+				"Error reading reg %lu\n", chan->address);
+			return ret;
+		}
+
+		*val = sign_extend32(reg, 7);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = MXC6255_SCALE;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info mxc6255_info = {
+	.driver_module	= THIS_MODULE,
+	.read_raw	= mxc6255_read_raw,
+};
+
+#define MXC6255_CHANNEL(_axis, reg) {				\
+	.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 mxc6255_channels[] = {
+	MXC6255_CHANNEL(X, MXC6255_REG_XOUT),
+	MXC6255_CHANNEL(Y, MXC6255_REG_YOUT),
+};
+
+static bool mxc6255_is_readable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MXC6255_REG_XOUT:
+	case MXC6255_REG_YOUT:
+	case MXC6255_REG_CHIP_ID:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config mxc6255_regmap_config = {
+	.name = MXC6255_REGMAP_NAME,
+
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.readable_reg = mxc6255_is_readable_reg,
+};
+
+static int mxc6255_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct mxc6255_data *data;
+	struct iio_dev *indio_dev;
+	struct regmap *regmap;
+	unsigned int chip_id;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	regmap = devm_regmap_init_i2c(client, &mxc6255_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "Error initializing regmap\n");
+		return PTR_ERR(regmap);
+	}
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	data->regmap = regmap;
+
+	indio_dev->name = MXC6255_DRV_NAME;
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->channels = mxc6255_channels;
+	indio_dev->num_channels = ARRAY_SIZE(mxc6255_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &mxc6255_info;
+
+	ret = regmap_read(data->regmap, MXC6255_REG_CHIP_ID, &chip_id);
+	if (ret < 0) {
+		dev_err(&client->dev, "Error reading chip id %d\n", ret);
+		return ret;
+	}
+
+	if (chip_id != MXC6255_CHIP_ID) {
+		dev_err(&client->dev, "Invalid chip id %x\n", chip_id);
+		return -ENODEV;
+	}
+
+	dev_dbg(&client->dev, "Chip id %x\n", chip_id);
+
+	ret = devm_iio_device_register(&client->dev, indio_dev);
+	if (ret < 0) {
+		dev_err(&client->dev, "Could not register IIO device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct acpi_device_id mxc6255_acpi_match[] = {
+	{"MXC6255",	0},
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, mxc6255_acpi_match);
+
+static const struct i2c_device_id mxc6255_id[] = {
+	{"mxc6255",	0},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mxc6255_id);
+
+static struct i2c_driver mxc6255_driver = {
+	.driver = {
+		.name = MXC6255_DRV_NAME,
+		.acpi_match_table = ACPI_PTR(mxc6255_acpi_match),
+	},
+	.probe		= mxc6255_probe,
+	.id_table	= mxc6255_id,
+};
+
+module_i2c_driver(mxc6255_driver);
+
+MODULE_AUTHOR("Teodora Baluta <teodora.baluta@intel.com>");
+MODULE_DESCRIPTION("MEMSIC MXC6255 orientation sensing accelerometer driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

Re: [PATCH v2] iio: accel: add support for Memsic MXC6255XC sensor

[Jonathan Cameron]

On 22/10/15 13:44, Teodora Baluta wrote:
> This patch adds a minimal implementation for the Memsic MXC6255XC
> orientation sensing accelerometer. The supported operations are reading
> raw acceleration values for X/Y axis that can be scaled using the
> exposed scale.
> 
> Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
Other than a tiny nitpick below (which I'll fix up when applying)
looks good to me.  Small and perfectly formed!

Jonathan
> ---
> Changes since v1:
> 
> - remove scale_available attribute
> - use chan->address instead
> - drop _AXIS_TO_REG macro
> - put register address in .address field of MXC6255_CHANNEL macro
> - check chip id
> - use "as follows" instead of "as following"
> 
>  drivers/iio/accel/Kconfig   |  11 +++
>  drivers/iio/accel/Makefile  |   1 +
>  drivers/iio/accel/mxc6255.c | 199 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 211 insertions(+)
>  create mode 100644 drivers/iio/accel/mxc6255.c
> 
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index 969428d..75ac087 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -158,6 +158,17 @@ config MXC4005
>  	  To compile this driver as a module, choose M. The module will be
>  	  called mxc4005.
>  
> +config MXC6255
> +	tristate "Memsic MXC6255 Orientation Sensing Accelerometer Driver"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  Say yes here to build support for the Memsic MXC6255 Orientation
> +	  Sensing Accelerometer Driver.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called mxc6255.
> +
>  config STK8312
>  	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
>  	depends on I2C
> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> index 7925f16..525ed52 100644
> --- a/drivers/iio/accel/Makefile
> +++ b/drivers/iio/accel/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_MMA9551)		+= mma9551.o
>  obj-$(CONFIG_MMA9553)		+= mma9553.o
>  
>  obj-$(CONFIG_MXC4005)		+= mxc4005.o
> +obj-$(CONFIG_MXC6255)		+= mxc6255.o
>  
>  obj-$(CONFIG_STK8312)		+= stk8312.o
>  obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
> diff --git a/drivers/iio/accel/mxc6255.c b/drivers/iio/accel/mxc6255.c
> new file mode 100644
> index 0000000..b853ff0
> --- /dev/null
> +++ b/drivers/iio/accel/mxc6255.c
> @@ -0,0 +1,199 @@
> +/*
> + * MXC6255 - MEMSIC orientation sensing accelerometer
> + *
> + * Copyright (c) 2015, 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.
> + *
> + * IIO driver for MXC6255 (7-bit I2C slave address 0x15).
No need for the blank line below.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/iio/iio.h>
> +#include <linux/delay.h>
> +#include <linux/acpi.h>
> +#include <linux/regmap.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define MXC6255_DRV_NAME		"mxc6255"
> +#define MXC6255_REGMAP_NAME		"mxc6255_regmap"
> +
> +#define MXC6255_REG_XOUT		0x00
> +#define MXC6255_REG_YOUT		0x01
> +#define MXC6255_REG_CHIP_ID		0x08
> +
> +#define MXC6255_CHIP_ID			0x05
> +
> +/*
> + * MXC6255 has only one measurement range: +/- 2G.
> + * The acceleration output is an 8-bit value.
> + *
> + * Scale is calculated as follows:
> + * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
> + *
> + * Scale value for +/- 2G measurement range
> + */
> +#define MXC6255_SCALE			153829
> +
> +enum mxc6255_axis {
> +	AXIS_X,
> +	AXIS_Y,
> +};
> +
> +struct mxc6255_data {
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +};
> +
> +static int mxc6255_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct mxc6255_data *data = iio_priv(indio_dev);
> +	unsigned int reg;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = regmap_read(data->regmap, chan->address, &reg);
> +		if (ret < 0) {
> +			dev_err(&data->client->dev,
> +				"Error reading reg %lu\n", chan->address);
> +			return ret;
> +		}
> +
> +		*val = sign_extend32(reg, 7);
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 0;
> +		*val2 = MXC6255_SCALE;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info mxc6255_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw	= mxc6255_read_raw,
> +};
> +
> +#define MXC6255_CHANNEL(_axis, reg) {				\
> +	.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 mxc6255_channels[] = {
> +	MXC6255_CHANNEL(X, MXC6255_REG_XOUT),
> +	MXC6255_CHANNEL(Y, MXC6255_REG_YOUT),
> +};
> +
> +static bool mxc6255_is_readable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case MXC6255_REG_XOUT:
> +	case MXC6255_REG_YOUT:
> +	case MXC6255_REG_CHIP_ID:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static const struct regmap_config mxc6255_regmap_config = {
> +	.name = MXC6255_REGMAP_NAME,
> +
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +
> +	.readable_reg = mxc6255_is_readable_reg,
> +};
> +
> +static int mxc6255_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct mxc6255_data *data;
> +	struct iio_dev *indio_dev;
> +	struct regmap *regmap;
> +	unsigned int chip_id;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	regmap = devm_regmap_init_i2c(client, &mxc6255_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		dev_err(&client->dev, "Error initializing regmap\n");
> +		return PTR_ERR(regmap);
> +	}
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +	data->regmap = regmap;
> +
> +	indio_dev->name = MXC6255_DRV_NAME;
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->channels = mxc6255_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(mxc6255_channels);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &mxc6255_info;
> +
> +	ret = regmap_read(data->regmap, MXC6255_REG_CHIP_ID, &chip_id);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Error reading chip id %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (chip_id != MXC6255_CHIP_ID) {
> +		dev_err(&client->dev, "Invalid chip id %x\n", chip_id);
> +		return -ENODEV;
> +	}
> +
> +	dev_dbg(&client->dev, "Chip id %x\n", chip_id);
> +
> +	ret = devm_iio_device_register(&client->dev, indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Could not register IIO device\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct acpi_device_id mxc6255_acpi_match[] = {
> +	{"MXC6255",	0},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, mxc6255_acpi_match);
> +
> +static const struct i2c_device_id mxc6255_id[] = {
> +	{"mxc6255",	0},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, mxc6255_id);
> +
> +static struct i2c_driver mxc6255_driver = {
> +	.driver = {
> +		.name = MXC6255_DRV_NAME,
> +		.acpi_match_table = ACPI_PTR(mxc6255_acpi_match),
> +	},
> +	.probe		= mxc6255_probe,
> +	.id_table	= mxc6255_id,
> +};
> +
> +module_i2c_driver(mxc6255_driver);
> +
> +MODULE_AUTHOR("Teodora Baluta <teodora.baluta@intel.com>");
> +MODULE_DESCRIPTION("MEMSIC MXC6255 orientation sensing accelerometer driver");
> +MODULE_LICENSE("GPL v2");
> 

Re: [PATCH v2] iio: accel: add support for Memsic MXC6255XC sensor

[Jonathan Cameron]

On 25/10/15 11:49, Jonathan Cameron wrote:
> On 22/10/15 13:44, Teodora Baluta wrote:
>> This patch adds a minimal implementation for the Memsic MXC6255XC
>> orientation sensing accelerometer. The supported operations are reading
>> raw acceleration values for X/Y axis that can be scaled using the
>> exposed scale.
>>
>> Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
> Other than a tiny nitpick below (which I'll fix up when applying)
> looks good to me.  Small and perfectly formed!
oops - forgot to say

Applied to the togreg branch of iio.git. Initially pushed out as testing
for the autobuilders to play with it.

Jonathan
> 
> Jonathan
>> ---
>> Changes since v1:
>>
>> - remove scale_available attribute
>> - use chan->address instead
>> - drop _AXIS_TO_REG macro
>> - put register address in .address field of MXC6255_CHANNEL macro
>> - check chip id
>> - use "as follows" instead of "as following"
>>
>>  drivers/iio/accel/Kconfig   |  11 +++
>>  drivers/iio/accel/Makefile  |   1 +
>>  drivers/iio/accel/mxc6255.c | 199 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 211 insertions(+)
>>  create mode 100644 drivers/iio/accel/mxc6255.c
>>
>> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
>> index 969428d..75ac087 100644
>> --- a/drivers/iio/accel/Kconfig
>> +++ b/drivers/iio/accel/Kconfig
>> @@ -158,6 +158,17 @@ config MXC4005
>>  	  To compile this driver as a module, choose M. The module will be
>>  	  called mxc4005.
>>  
>> +config MXC6255
>> +	tristate "Memsic MXC6255 Orientation Sensing Accelerometer Driver"
>> +	depends on I2C
>> +	select REGMAP_I2C
>> +	help
>> +	  Say yes here to build support for the Memsic MXC6255 Orientation
>> +	  Sensing Accelerometer Driver.
>> +
>> +	  To compile this driver as a module, choose M here: the module will be
>> +	  called mxc6255.
>> +
>>  config STK8312
>>  	tristate "Sensortek STK8312 3-Axis Accelerometer Driver"
>>  	depends on I2C
>> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
>> index 7925f16..525ed52 100644
>> --- a/drivers/iio/accel/Makefile
>> +++ b/drivers/iio/accel/Makefile
>> @@ -17,6 +17,7 @@ obj-$(CONFIG_MMA9551)		+= mma9551.o
>>  obj-$(CONFIG_MMA9553)		+= mma9553.o
>>  
>>  obj-$(CONFIG_MXC4005)		+= mxc4005.o
>> +obj-$(CONFIG_MXC6255)		+= mxc6255.o
>>  
>>  obj-$(CONFIG_STK8312)		+= stk8312.o
>>  obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
>> diff --git a/drivers/iio/accel/mxc6255.c b/drivers/iio/accel/mxc6255.c
>> new file mode 100644
>> index 0000000..b853ff0
>> --- /dev/null
>> +++ b/drivers/iio/accel/mxc6255.c
>> @@ -0,0 +1,199 @@
>> +/*
>> + * MXC6255 - MEMSIC orientation sensing accelerometer
>> + *
>> + * Copyright (c) 2015, 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.
>> + *
>> + * IIO driver for MXC6255 (7-bit I2C slave address 0x15).
> No need for the blank line below.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/i2c.h>
>> +#include <linux/init.h>
>> +#include <linux/iio/iio.h>
>> +#include <linux/delay.h>
>> +#include <linux/acpi.h>
>> +#include <linux/regmap.h>
>> +#include <linux/iio/sysfs.h>
>> +
>> +#define MXC6255_DRV_NAME		"mxc6255"
>> +#define MXC6255_REGMAP_NAME		"mxc6255_regmap"
>> +
>> +#define MXC6255_REG_XOUT		0x00
>> +#define MXC6255_REG_YOUT		0x01
>> +#define MXC6255_REG_CHIP_ID		0x08
>> +
>> +#define MXC6255_CHIP_ID			0x05
>> +
>> +/*
>> + * MXC6255 has only one measurement range: +/- 2G.
>> + * The acceleration output is an 8-bit value.
>> + *
>> + * Scale is calculated as follows:
>> + * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
>> + *
>> + * Scale value for +/- 2G measurement range
>> + */
>> +#define MXC6255_SCALE			153829
>> +
>> +enum mxc6255_axis {
>> +	AXIS_X,
>> +	AXIS_Y,
>> +};
>> +
>> +struct mxc6255_data {
>> +	struct i2c_client *client;
>> +	struct regmap *regmap;
>> +};
>> +
>> +static int mxc6255_read_raw(struct iio_dev *indio_dev,
>> +			    struct iio_chan_spec const *chan,
>> +			    int *val, int *val2, long mask)
>> +{
>> +	struct mxc6255_data *data = iio_priv(indio_dev);
>> +	unsigned int reg;
>> +	int ret;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		ret = regmap_read(data->regmap, chan->address, &reg);
>> +		if (ret < 0) {
>> +			dev_err(&data->client->dev,
>> +				"Error reading reg %lu\n", chan->address);
>> +			return ret;
>> +		}
>> +
>> +		*val = sign_extend32(reg, 7);
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_SCALE:
>> +		*val = 0;
>> +		*val2 = MXC6255_SCALE;
>> +		return IIO_VAL_INT_PLUS_MICRO;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static const struct iio_info mxc6255_info = {
>> +	.driver_module	= THIS_MODULE,
>> +	.read_raw	= mxc6255_read_raw,
>> +};
>> +
>> +#define MXC6255_CHANNEL(_axis, reg) {				\
>> +	.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 mxc6255_channels[] = {
>> +	MXC6255_CHANNEL(X, MXC6255_REG_XOUT),
>> +	MXC6255_CHANNEL(Y, MXC6255_REG_YOUT),
>> +};
>> +
>> +static bool mxc6255_is_readable_reg(struct device *dev, unsigned int reg)
>> +{
>> +	switch (reg) {
>> +	case MXC6255_REG_XOUT:
>> +	case MXC6255_REG_YOUT:
>> +	case MXC6255_REG_CHIP_ID:
>> +		return true;
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +static const struct regmap_config mxc6255_regmap_config = {
>> +	.name = MXC6255_REGMAP_NAME,
>> +
>> +	.reg_bits = 8,
>> +	.val_bits = 8,
>> +
>> +	.readable_reg = mxc6255_is_readable_reg,
>> +};
>> +
>> +static int mxc6255_probe(struct i2c_client *client,
>> +			 const struct i2c_device_id *id)
>> +{
>> +	struct mxc6255_data *data;
>> +	struct iio_dev *indio_dev;
>> +	struct regmap *regmap;
>> +	unsigned int chip_id;
>> +	int ret;
>> +
>> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>> +	if (!indio_dev)
>> +		return -ENOMEM;
>> +
>> +	regmap = devm_regmap_init_i2c(client, &mxc6255_regmap_config);
>> +	if (IS_ERR(regmap)) {
>> +		dev_err(&client->dev, "Error initializing regmap\n");
>> +		return PTR_ERR(regmap);
>> +	}
>> +
>> +	data = iio_priv(indio_dev);
>> +	i2c_set_clientdata(client, indio_dev);
>> +	data->client = client;
>> +	data->regmap = regmap;
>> +
>> +	indio_dev->name = MXC6255_DRV_NAME;
>> +	indio_dev->dev.parent = &client->dev;
>> +	indio_dev->channels = mxc6255_channels;
>> +	indio_dev->num_channels = ARRAY_SIZE(mxc6255_channels);
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +	indio_dev->info = &mxc6255_info;
>> +
>> +	ret = regmap_read(data->regmap, MXC6255_REG_CHIP_ID, &chip_id);
>> +	if (ret < 0) {
>> +		dev_err(&client->dev, "Error reading chip id %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	if (chip_id != MXC6255_CHIP_ID) {
>> +		dev_err(&client->dev, "Invalid chip id %x\n", chip_id);
>> +		return -ENODEV;
>> +	}
>> +
>> +	dev_dbg(&client->dev, "Chip id %x\n", chip_id);
>> +
>> +	ret = devm_iio_device_register(&client->dev, indio_dev);
>> +	if (ret < 0) {
>> +		dev_err(&client->dev, "Could not register IIO device\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct acpi_device_id mxc6255_acpi_match[] = {
>> +	{"MXC6255",	0},
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(acpi, mxc6255_acpi_match);
>> +
>> +static const struct i2c_device_id mxc6255_id[] = {
>> +	{"mxc6255",	0},
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(i2c, mxc6255_id);
>> +
>> +static struct i2c_driver mxc6255_driver = {
>> +	.driver = {
>> +		.name = MXC6255_DRV_NAME,
>> +		.acpi_match_table = ACPI_PTR(mxc6255_acpi_match),
>> +	},
>> +	.probe		= mxc6255_probe,
>> +	.id_table	= mxc6255_id,
>> +};
>> +
>> +module_i2c_driver(mxc6255_driver);
>> +
>> +MODULE_AUTHOR("Teodora Baluta <teodora.baluta@intel.com>");
>> +MODULE_DESCRIPTION("MEMSIC MXC6255 orientation sensing accelerometer driver");
>> +MODULE_LICENSE("GPL v2");
>>
> 
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