Re: [PATCH] iio: accel: add support for the Domintech DMARD09 3-axis accelerometer

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> Minimal implementation of an IIO driver for the Domintech DMARD09 3-axis
> accelerometer. Only supports reading the x,y,z axes at the moment.

comments below

> Implementation based on the Android driver from the Acer Liquid E2
> kernel sources.
> 
> Signed-off-by: Jelle van der Waa <jelle@xxxxxxxx>
> ---
>  .../devicetree/bindings/iio/accel/dmard09.txt      |  13 ++
>  drivers/iio/accel/Kconfig                          |  10 ++
>  drivers/iio/accel/Makefile                         |   1 +
>  drivers/iio/accel/dmard09.c                        | 180 +++++++++++++++++++++
>  4 files changed, 204 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/accel/dmard09.txt
>  create mode 100644 drivers/iio/accel/dmard09.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/accel/dmard09.txt b/Documentation/devicetree/bindings/iio/accel/dmard09.txt
> new file mode 100644
> index 0000000..69b2a03
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/accel/dmard09.txt
> @@ -0,0 +1,13 @@
> +Domintech DMARD09 accelerometer devicetree bindings
> +
> +Required properties:
> +
> +  - compatible : should be "domintech,dmard09"
> +  - reg : the I2C address of the sensor
> +
> +Example:
> +
> +dmard09@0x1d {
> +	compatible = "domintech,dmard09";
> +	reg = <0x1d>;
> +};
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index e4a758c..3fb16eb 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -40,6 +40,16 @@ config BMC150_ACCEL_SPI
>  	tristate
>  	select REGMAP_SPI
>  
> +config DMARD09
> +	tristate "Domintech DMARD09 3-axis Accelerometer Driver"
> +	select I2C
> +	help
> +	  Say yes here to get support for the Domintech DMARD09 3-axis
> +	  accelerometer.
> +
> +	  Choosing M will build the driver as a module. If so, the module
> +	  will be called dmard09.
> +
>  config HID_SENSOR_ACCEL_3D
>  	depends on HID_SENSOR_HUB
>  	select IIO_BUFFER
> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> index 71b6794..b1022a0 100644
> --- a/drivers/iio/accel/Makefile
> +++ b/drivers/iio/accel/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_BMA180) += bma180.o
>  obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o
>  obj-$(CONFIG_BMC150_ACCEL_I2C) += bmc150-accel-i2c.o
>  obj-$(CONFIG_BMC150_ACCEL_SPI) += bmc150-accel-spi.o
> +obj-$(CONFIG_DMARD09) += dmard09.o
>  obj-$(CONFIG_HID_SENSOR_ACCEL_3D) += hid-sensor-accel-3d.o
>  obj-$(CONFIG_KXCJK1013) += kxcjk-1013.o
>  obj-$(CONFIG_KXSD9)	+= kxsd9.o
> diff --git a/drivers/iio/accel/dmard09.c b/drivers/iio/accel/dmard09.c
> new file mode 100644
> index 0000000..8689c5a
> --- /dev/null
> +++ b/drivers/iio/accel/dmard09.c
> @@ -0,0 +1,180 @@
> +/*
> + *  3-axis accelerometer driver for DMARD09 3-axis sensor.

remove extra space at beginning of line
3-axis mentioned twice

> + *
> + * Copyright (c) 2016, Jelle van der Waa <jelle@xxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +
> +#define DMARD09_DRV_NAME	"dmard09"
> +
> +#define DMARD09_REG_CHIPID      0x18
> +#define DMARD09_REG_STAT	0x0A
> +#define DMARD09_REG_X		0x0C
> +#define DMARD09_REG_Y		0x0E
> +#define DMARD09_REG_Z		0x10
> +#define DMARD09_CHIPID		0x95
> +
> +#define DMARD09_BUF_LEN 8
> +#define DMARD09_AXES_NUM        3
> +#define DMARD09_AXIS_X 0
> +#define DMARD09_AXIS_Y 1
> +#define DMARD09_AXIS_Z 2
> +
> +/* Used for dev_info() */
> +struct dmard09_data {
> +	struct i2c_client *client;
> +	struct device *dev;
what is this good for? use client->dev?
> +};
> +
> +static const struct iio_chan_spec dmard09_channels[] = {

a #define would help to write this in a more concise way

> +	{
> +		.type = IIO_ACCEL,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.modified = 1,
> +		.address = DMARD09_REG_X,

I suggest to store _AXIS_N here or rather AXIS_N_OFFSET which would be 
(AXIS+1)*2

> +		.channel2 = IIO_MOD_X,
> +	},
> +	{
> +		.type = IIO_ACCEL,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.modified = 1,
> +		.address = DMARD09_REG_Y,
> +		.channel2 = IIO_MOD_Y,
> +	},
> +	{
> +		.type = IIO_ACCEL,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.modified = 1,
> +		.address = DMARD09_REG_Z,
> +		.channel2 = IIO_MOD_Z,
> +	}
> +};
> +
> +static int dmard09_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct dmard09_data *data = iio_priv(indio_dev);
> +	u8 buf[DMARD09_BUF_LEN] = {0};

why initialize buf?

> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = i2c_smbus_read_i2c_block_data(data->client,
> +						    DMARD09_REG_STAT,
> +						    DMARD09_BUF_LEN, buf);
> +		if (ret < 0) {

a comment explaining the read stragegy would be nice

I guess that _STAT would have some information if the data is 
ready/valid? why not start reading at AXIS_X?

> +			dev_err(data->dev, "Error reading reg %lu\n",
> +				chan->address);
> +			return ret;
> +		}
> +

check stat?
the if block is not necessary, maybe
*val = (s16) le16_to_cpup(&buf[chan->address])
where chan->address is the offset into buf

> +		if (chan->address == DMARD09_REG_X)
> +			*val = (s16)((buf[(DMARD09_AXIS_X+1)*2+1] << 8)
> +					| (buf[(DMARD09_AXIS_X+1)*2]));
> +		if (chan->address == DMARD09_REG_Y)
> +			*val = (s16)((buf[(DMARD09_AXIS_Y+1)*2+1] << 8)
> +					| (buf[(DMARD09_AXIS_Y+1)*2]));
> +		if (chan->address == DMARD09_REG_Z)
> +			*val = (s16)((buf[(DMARD09_AXIS_Z+1)*2+1] << 8)
> +					| (buf[(DMARD09_AXIS_Z+1)*2]));
> +
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_info dmard09_info = {
> +	.driver_module	= THIS_MODULE,
> +	.read_raw	= dmard09_read_raw,
> +};
> +
> +static int dmard09_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	int ret;
> +	struct iio_dev *indio_dev;
> +	struct dmard09_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->dev = &client->dev;
> +	data->client = client;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, DMARD09_REG_CHIPID);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Error reading chip id %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (ret != DMARD09_CHIPID) {
> +		dev_err(&client->dev, "Invalid chip id %d\n", ret);
> +		return -ENODEV;
> +	}
> +
> +	i2c_set_clientdata(client, indio_dev);
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = DMARD09_DRV_NAME;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = dmard09_channels;
> +	indio_dev->num_channels = DMARD09_AXES_NUM;

I suggest ARRAY_SIZE(dmard09_channels)

> +	indio_dev->info = &dmard09_info;
> +
> +	ret = iio_device_register(indio_dev);


could use devm_iio_device_register, just 
return devm_iio_device_register(...) and drop the if

> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int dmard09_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 dmard09_id[] = {
> +	{ "dmard09", 0},
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, dmard09_id);
> +
> +static struct i2c_driver dmard09_driver = {
> +	.driver = {
> +		.name = DMARD09_DRV_NAME
> +	},
> +	.probe = dmard09_probe,
> +	.remove = dmard09_remove,
> +	.id_table = dmard09_id,
> +};
> +
> +module_i2c_driver(dmard09_driver);
> +
> +MODULE_AUTHOR("Jelle van der Waa <jelle@xxxxxxxx>");
> +MODULE_DESCRIPTION("DMARD09 3-axis accelerometer driver");
> +MODULE_LICENSE("GPL");
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)
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