Re: [PATCH] iio: Add LTC2471/LTC2473 driver

[Peter Meerwald-Stadler]

> The LTC2741 and LTC2473 are single voltage ADC chips. The LTC2473
> is similar to the LTC2471 but outputs a signed differential value.

comments below
 
> Datasheet:
>   http://cds.linear.com/docs/en/datasheet/24713fb.pdf
> 
> Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> ---
> Note: Moved from "hwmon" subsystem to "iio" as discussed per e-mail,
> see also: https://patchwork.kernel.org/patch/9816607/
> Only tested the LTC2741 in real life.
> 
>  drivers/iio/adc/Kconfig   |  10 +++
>  drivers/iio/adc/Makefile  |   1 +
>  drivers/iio/adc/ltc2471.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 174 insertions(+)
>  create mode 100644 drivers/iio/adc/ltc2471.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 401f47b..fbee44a 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -362,6 +362,16 @@ config LPC32XX_ADC
>  	  activate only one via device tree selection.  Provides direct access
>  	  via sysfs.
>  
> +config LTC2471
> +	tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for Linear Technology LTC2471 and
> +	  LTC2473 ADC.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ltc2471.
> +
>  config LTC2485
>  	tristate "Linear Technology LTC2485 ADC driver"
>  	depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 9339bec..afafe85 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
>  obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
>  obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
>  obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
> +obj-$(CONFIG_LTC2471) += ltc2471.o
>  obj-$(CONFIG_LTC2485) += ltc2485.o
>  obj-$(CONFIG_LTC2497) += ltc2497.o
>  obj-$(CONFIG_MAX1027) += max1027.o
> diff --git a/drivers/iio/adc/ltc2471.c b/drivers/iio/adc/ltc2471.c
> new file mode 100644
> index 0000000..f26bdad
> --- /dev/null
> +++ b/drivers/iio/adc/ltc2471.c
> @@ -0,0 +1,163 @@
> +/*
> + * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
> + * The LTC2473 is identical to the 2471, but reports a differential signal.
> + *
> + * Copyright (C) 2017 Topic Embedded Products
> + * Author: Mike Looijmans <mike.looijmans@xxxxxxxx>
> + *
> + * License: GPLv2
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +enum chips {

ltc2471_ prefix please

> +	ltc2471,
> +	ltc2473

end last line with a comma, so additions can be done with a one-line patch

> +};
> +
> +struct ltc2471_data {
> +	struct i2c_client *client;
> +};
> +
> +/* Reference voltage is 1.25V */
> +#define LTC2471_VREF 1250
> +
> +/* Read two bytes from the I2C bus to obtain the ADC result */
> +static int ltc2471_get_value(struct i2c_client *client)
> +{
> +	int ret;
> +	__be16 buf;
> +
> +	ret = i2c_master_recv(client, (char *)&buf, 2);

sizeof(buf) probably

> +	if (ret < 0)
> +		return ret;
> +	if (ret != 2)

sizeof(buf) probably

> +		return -EIO;
> +
> +	/* MSB first */
> +	return be16_to_cpu(buf);
> +}
> +
> +static int ltc2471_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long info)
> +{
> +	struct ltc2471_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = ltc2471_get_value(data->client);
> +		if (ret < 0)
> +			return ret;
> +		*val = ret;
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		if (chan->differential)
> +			/* Output ranges from -VREF to +VREF */
> +			*val = 2 * LTC2471_VREF;
> +		else
> +			/* Output ranges from 0 to VREF */
> +			*val = LTC2471_VREF;
> +		*val2 = 16;	/* 16 data bits */
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		if (chan->differential)
> +			*val = -LTC2471_VREF;
> +		else
> +			*val = 0;

the non-differential (single ended) chip has no offset channel anyway 
according to iio_chan_spec...

> +		return IIO_VAL_INT;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct iio_chan_spec ltc2471_channel[] = {
> +	{
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +		.differential = 0,

.differential = 0 not needed

> +	},
> +};
> +static const struct iio_chan_spec ltc2473_channel[] = {
> +	{
> +		.type = IIO_VOLTAGE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
> +					    BIT(IIO_CHAN_INFO_OFFSET),
> +		.differential = 1,
> +	},
> +};
> +
> +static const struct iio_info ltc2471_info = {
> +	.read_raw = ltc2471_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int ltc2471_i2c_probe(struct i2c_client *client,
> +			     const struct i2c_device_id *id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct ltc2471_data *data;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> +		return -EOPNOTSUPP;
> +
> +	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;
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = id->name;
> +	indio_dev->info = &ltc2471_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	if (id->driver_data == ltc2473)
> +		indio_dev->channels = ltc2473_channel;
> +	else
> +		indio_dev->channels = ltc2471_channel;
> +	indio_dev->num_channels = 1;
> +
> +	/* Trigger once to start conversion and check if chip is there */
> +	ret = ltc2471_get_value(client);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Cannot read from device.\n");
> +		return ret;
> +	}
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id ltc2471_i2c_id[] = {
> +	{ "ltc2471", ltc2471 },
> +	{ "ltc2473", ltc2473 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
> +
> +static struct i2c_driver ltc2471_i2c_driver = {
> +	.driver = {
> +		.name = "ltc2471",
> +	},
> +	.probe    = ltc2471_i2c_probe,
> +	.id_table = ltc2471_i2c_id,
> +};
> +
> +module_i2c_driver(ltc2471_i2c_driver);
> +
> +MODULE_DESCRIPTION("LTC2471/LTC2473 Sensor Driver");

maybe "ADC driver"

> +MODULE_AUTHOR("Topic Embedded Products");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
Mobile: +43 664 24 44 418