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

[PATCH] 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>
---
 drivers/iio/accel/Kconfig   |  11 +++
 drivers/iio/accel/Makefile  |   1 +
 drivers/iio/accel/mxc6255.c | 210 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 222 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..ed0f1ab
--- /dev/null
+++ b/drivers/iio/accel/mxc6255.c
@@ -0,0 +1,210 @@
+/*
+ * 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_AXIS_TO_REG(axis)	(MXC6255_REG_XOUT + axis)
+
+/*
+ * MXC6255 has only one measurement range: +/- 2G.
+ * The acceleration output is an 8-bit value.
+ *
+ * Scale is calculated as following:
+ * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
+ *
+ */
+#define MXC6255_SCALE_AVAIL		"0.153829"
+
+enum mxc6255_axis {
+	AXIS_X,
+	AXIS_Y,
+};
+
+struct mxc6255_data {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+/* scale value for +/- 2G measurement range */
+static const int mxc6255_scale = 153829;
+
+static IIO_CONST_ATTR(in_accel_scale_available, MXC6255_SCALE_AVAIL);
+
+static struct attribute *mxc6255_attributes[] = {
+	&iio_const_attr_in_accel_scale_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group mxc6255_attribute_group = {
+	.attrs = mxc6255_attributes
+};
+
+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 axis = chan->channel2 - 1;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = regmap_read(data->regmap,
+				  MXC6255_AXIS_TO_REG(axis), &reg);
+		if (ret < 0) {
+			dev_err(&data->client->dev,
+				"Error reading axis %d\n", axis);
+			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,
+	.attrs		= &mxc6255_attribute_group,
+};
+
+#define MXC6255_CHANNEL(_axis) {				\
+	.type = IIO_ACCEL,					\
+	.modified = 1,						\
+	.channel2 = IIO_MOD_##_axis,				\
+	.address = AXIS_##_axis,				\
+	.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_CHANNEL(Y),
+};
+
+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;
+	}
+
+	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] iio: accel: add support for Memsic MXC6255XC sensor

[Lars-Peter Clausen]

On 10/16/2015 12:29 PM, 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>

Looks quite good in general, a few minor things inline.

[...]
> +/* scale value for +/- 2G measurement range */
> +static const int mxc6255_scale = 153829;
> +
> +static IIO_CONST_ATTR(in_accel_scale_available, MXC6255_SCALE_AVAIL);

If there is only one scale available it does not make too much sense to have
a scale_available attribute.

[..]
> +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 axis = chan->channel2 - 1;

1 is a bit of a magic constant here. Use IIO_MOD_X instead. Or even better
use chan->address.

> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = regmap_read(data->regmap,
> +				  MXC6255_AXIS_TO_REG(axis), &reg);
> +		if (ret < 0) {
> +			dev_err(&data->client->dev,
> +				"Error reading axis %d\n", axis);
> +			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 int mxc6255_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
[...]
> +	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;
> +	}

Does it make sense to check whether chip ID matches the expected value, to
catch mistakes where the I2C address is incorrect?

> +
> +	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;
> +}
[...]

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

[Peter Meerwald]

On Fri, 16 Oct 2015, 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.

minor comments below
link to datasheet?
 
> Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
> ---
>  drivers/iio/accel/Kconfig   |  11 +++
>  drivers/iio/accel/Makefile  |   1 +
>  drivers/iio/accel/mxc6255.c | 210 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 222 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..ed0f1ab
> --- /dev/null
> +++ b/drivers/iio/accel/mxc6255.c
> @@ -0,0 +1,210 @@
> +/*
> + * 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_AXIS_TO_REG(axis)	(MXC6255_REG_XOUT + axis)
> +
> +/*
> + * MXC6255 has only one measurement range: +/- 2G.
> + * The acceleration output is an 8-bit value.

is a

> + *
> + * Scale is calculated as following:

as follows

> + * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
> + *
> + */
> +#define MXC6255_SCALE_AVAIL		"0.153829"
> +
> +enum mxc6255_axis {
> +	AXIS_X,
> +	AXIS_Y,
> +};
> +
> +struct mxc6255_data {
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +};
> +
> +/* scale value for +/- 2G measurement range */
> +static const int mxc6255_scale = 153829;

it is customary to use a #define

> +
> +static IIO_CONST_ATTR(in_accel_scale_available, MXC6255_SCALE_AVAIL);
> +
> +static struct attribute *mxc6255_attributes[] = {
> +	&iio_const_attr_in_accel_scale_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group mxc6255_attribute_group = {
> +	.attrs = mxc6255_attributes
> +};
> +
> +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 axis = chan->channel2 - 1;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = regmap_read(data->regmap,
> +				  MXC6255_AXIS_TO_REG(axis), &reg);

use chan->address, and drop the _AXIS_TO_REG macro and axis variable

> +		if (ret < 0) {
> +			dev_err(&data->client->dev,
> +				"Error reading axis %d\n", axis);
> +			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,
> +	.attrs		= &mxc6255_attribute_group,
> +};
> +
> +#define MXC6255_CHANNEL(_axis) {				\
> +	.type = IIO_ACCEL,					\
> +	.modified = 1,						\
> +	.channel2 = IIO_MOD_##_axis,				\
> +	.address = AXIS_##_axis,				\

put MXC6255_REG_XOUT / MXC6255_REG_YOUT here, add parameter to _CHANNEL 
macro

> +	.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_CHANNEL(Y),
> +};
> +
> +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;
> +	}
> +
> +	dev_dbg(&client->dev, "Chip id %x\n", chip_id);

maybe check 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");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)

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

[Teodora Baluta]

On Mon, Oct 19, 2015 at 12:52:50PM +0200, Lars-Peter Clausen wrote:
> On 10/16/2015 12:29 PM, 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>
> 
> Looks quite good in general, a few minor things inline.

Thanks for the review. I'll send a v2 as soon as possible.

> 
> [...]
> > +/* scale value for +/- 2G measurement range */
> > +static const int mxc6255_scale = 153829;
> > +
> > +static IIO_CONST_ATTR(in_accel_scale_available, MXC6255_SCALE_AVAIL);
> 
> If there is only one scale available it does not make too much sense to have
> a scale_available attribute.
> 
> [..]
> > +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 axis = chan->channel2 - 1;
> 
> 1 is a bit of a magic constant here. Use IIO_MOD_X instead. Or even better
> use chan->address.
> 
> > +	int ret;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		ret = regmap_read(data->regmap,
> > +				  MXC6255_AXIS_TO_REG(axis), &reg);
> > +		if (ret < 0) {
> > +			dev_err(&data->client->dev,
> > +				"Error reading axis %d\n", axis);
> > +			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 int mxc6255_probe(struct i2c_client *client,
> > +			 const struct i2c_device_id *id)
> > +{
> [...]
> > +	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;
> > +	}
> 
> Does it make sense to check whether chip ID matches the expected value, to
> catch mistakes where the I2C address is incorrect?
> 
> > +
> > +	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;
> > +}
> [...]

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

[Teodora Baluta]

On Mon, Oct 19, 2015 at 01:08:50PM +0200, Peter Meerwald wrote:
> On Fri, 16 Oct 2015, 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.
> 
> minor comments below
> link to datasheet?

The datasheet is not public. I've asked Memsic if they can make the
datasheet public or if we can distribute a private copy on request.

I'll address the comments in the v2 patch. Thanks for the review!

>  
> > Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
> > ---
> >  drivers/iio/accel/Kconfig   |  11 +++
> >  drivers/iio/accel/Makefile  |   1 +
> >  drivers/iio/accel/mxc6255.c | 210 ++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 222 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..ed0f1ab
> > --- /dev/null
> > +++ b/drivers/iio/accel/mxc6255.c
> > @@ -0,0 +1,210 @@
> > +/*
> > + * 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_AXIS_TO_REG(axis)	(MXC6255_REG_XOUT + axis)
> > +
> > +/*
> > + * MXC6255 has only one measurement range: +/- 2G.
> > + * The acceleration output is an 8-bit value.
> 
> is a

I think it came from "an eight-bit value", so "is an" sounds right to
me.

> 
> > + *
> > + * Scale is calculated as following:
> 
> as follows
> 
> > + * (2 + 2) * 9.80665 / (2^8 - 1) = 0.153829
> > + *
> > + */
> > +#define MXC6255_SCALE_AVAIL		"0.153829"
> > +
> > +enum mxc6255_axis {
> > +	AXIS_X,
> > +	AXIS_Y,
> > +};
> > +
> > +struct mxc6255_data {
> > +	struct i2c_client *client;
> > +	struct regmap *regmap;
> > +};
> > +
> > +/* scale value for +/- 2G measurement range */
> > +static const int mxc6255_scale = 153829;
> 
> it is customary to use a #define
> 
> > +
> > +static IIO_CONST_ATTR(in_accel_scale_available, MXC6255_SCALE_AVAIL);
> > +
> > +static struct attribute *mxc6255_attributes[] = {
> > +	&iio_const_attr_in_accel_scale_available.dev_attr.attr,
> > +	NULL,
> > +};
> > +
> > +static const struct attribute_group mxc6255_attribute_group = {
> > +	.attrs = mxc6255_attributes
> > +};
> > +
> > +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 axis = chan->channel2 - 1;
> > +	int ret;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		ret = regmap_read(data->regmap,
> > +				  MXC6255_AXIS_TO_REG(axis), &reg);
> 
> use chan->address, and drop the _AXIS_TO_REG macro and axis variable
> 
> > +		if (ret < 0) {
> > +			dev_err(&data->client->dev,
> > +				"Error reading axis %d\n", axis);
> > +			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,
> > +	.attrs		= &mxc6255_attribute_group,
> > +};
> > +
> > +#define MXC6255_CHANNEL(_axis) {				\
> > +	.type = IIO_ACCEL,					\
> > +	.modified = 1,						\
> > +	.channel2 = IIO_MOD_##_axis,				\
> > +	.address = AXIS_##_axis,				\
> 
> put MXC6255_REG_XOUT / MXC6255_REG_YOUT here, add parameter to _CHANNEL 
> macro
> 
> > +	.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_CHANNEL(Y),
> > +};
> > +
> > +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;
> > +	}
> > +
> > +	dev_dbg(&client->dev, "Chip id %x\n", chip_id);
> 
> maybe check chip id?

Will do.

> 
> > +
> > +	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");
> > 
> 
> -- 
> 
> Peter Meerwald
> +43-664-2444418 (mobile)