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

[Frans Klaver]

On Thu, Jun 29, 2017 at 12:45 PM, Mike Looijmans
<mike.looijmans@xxxxxxxx> wrote:
> The LTC2741 and LTC2473 are single voltage monitoring chips. The LTC2473
> is similar to the LTC2471 but outputs a signed differential value.
>
> Datasheet:
>   http://cds.linear.com/docs/en/datasheet/24713fb.pdf
>
> Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> ---
>  drivers/hwmon/Kconfig   |  10 ++++
>  drivers/hwmon/Makefile  |   1 +
>  drivers/hwmon/ltc2471.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 138 insertions(+)
>  create mode 100644 drivers/hwmon/ltc2471.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index fbde226..c9a2a87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -673,6 +673,16 @@ config SENSORS_LINEAGE
>           This driver can also be built as a module.  If so, the module
>           will be called lineage-pem.
>
> +config SENSORS_LTC2471
> +       tristate "Linear Technology LTC2471 and LTC2473"
> +       depends on I2C
> +       help
> +         If you say yes here you get support for Linear Technology LTC2471
> +         and LTC2473 voltage monitors.
> +
> +         This driver can also be built as a module. If so, the module will
> +         be called ltc2471.
> +
>  config SENSORS_LTC2945
>         tristate "Linear Technology LTC2945"
>         depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 58cc3ac..6f60fe7 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -99,6 +99,7 @@ obj-$(CONFIG_SENSORS_LM93)    += lm93.o
>  obj-$(CONFIG_SENSORS_LM95234)  += lm95234.o
>  obj-$(CONFIG_SENSORS_LM95241)  += lm95241.o
>  obj-$(CONFIG_SENSORS_LM95245)  += lm95245.o
> +obj-$(CONFIG_SENSORS_LTC2471)  += ltc2471.o
>  obj-$(CONFIG_SENSORS_LTC2945)  += ltc2945.o
>  obj-$(CONFIG_SENSORS_LTC2990)  += ltc2990.o
>  obj-$(CONFIG_SENSORS_LTC4151)  += ltc4151.o
> diff --git a/drivers/hwmon/ltc2471.c b/drivers/hwmon/ltc2471.c
> new file mode 100644
> index 0000000..17eaad8
> --- /dev/null
> +++ b/drivers/hwmon/ltc2471.c
> @@ -0,0 +1,127 @@
> +/*
> + * 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/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +enum chips {
> +       ltc2471,
> +       ltc2473
> +};
> +
> +struct ltc2471_data {
> +       struct i2c_client *i2c;
> +       bool differential;
> +};

I haven't checked if there are similar drivers, but how about
ltc247x_data? It's a bit odd to tie all naming in this driver to one
chip and then support another one as well.

> +
> +/* 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 *i2c)
> +{
> +       int ret;
> +       __be16 buf;
> +
> +       ret = i2c_master_recv(i2c, (char *)&buf, 2);
> +       if (ret < 0)
> +               return ret;
> +       if (ret != 2)
> +               return -EIO;
> +
> +       /* MSB first */
> +       return be16_to_cpu(buf);
> +}
> +
> +static ssize_t ltc2471_show_value(struct device *dev,
> +                                 struct device_attribute *da, char *buf)
> +{
> +       struct ltc2471_data *data = dev_get_drvdata(dev);
> +       int value;
> +
> +       value = ltc2471_get_value(data->i2c);
> +       if (unlikely(value < 0))
> +               return value;
> +
> +       if (data->differential)
> +               /* Ranges from -VREF to +VREF with "0" at 0x8000 */
> +               value = ((s32)LTC2471_VREF * (s32)(value - 0x8000)) >> 15;
> +       else
> +               /* Ranges from 0 to +VREF */
> +               value = ((u32)LTC2471_VREF * (u32)value) >> 16;
> +
> +       return snprintf(buf, PAGE_SIZE, "%d\n", value);
> +}
> +
> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2471_show_value, NULL, 0);

Octal permissions are preferred over S_IRUGO and such.

> +
> +static struct attribute *ltc2471_attrs[] = {
> +       &sensor_dev_attr_in0_input.dev_attr.attr,
> +       NULL
> +};
> +
> +ATTRIBUTE_GROUPS(ltc2471);
> +
> +static int ltc2471_i2c_probe(struct i2c_client *i2c,
> +                            const struct i2c_device_id *id)
> +{
> +       int ret;
> +       struct device *hwmon_dev;
> +       struct ltc2471_data *data;
> +
> +       if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
> +               return -ENODEV;
> +
> +       data = devm_kzalloc(&i2c->dev, sizeof(struct ltc2471_data), GFP_KERNEL);

sizeof(*data)

> +       if (unlikely(!data))
> +               return -ENOMEM;
> +
> +       data->i2c = i2c;
> +       data->differential = (id->driver_data == ltc2473);
> +
> +       /* Trigger once to start conversion and check if chip is there */
> +       ret = ltc2471_get_value(i2c);
> +       if (ret < 0) {
> +               dev_err(&i2c->dev, "Cannot read from device.\n");
> +               return ret;
> +       }
> +
> +       hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
> +                                                          i2c->name,
> +                                                          data,
> +                                                          ltc2471_groups);
> +
> +       return PTR_ERR_OR_ZERO(hwmon_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");
> +MODULE_AUTHOR("Topic Embedded Products");
> +MODULE_LICENSE("GPL v2");
> --
> 1.9.1
>

Frans