linux-imx

/*

 * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver

 * Copyright 2016 Rockwell Collins

 *

 * Datasheet:

 * http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the gnu general public license version 2 as

 * published by the free software foundation.

 *

 */

​

#include <linux/acpi.h>

#include <linux/iio/iio.h>

#include <linux/iio/sysfs.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/of_device.h>

#include <linux/spi/spi.h>

​

/* write wiper reg */

#define MAX5481_WRITE_WIPER (0 << 4)

/* copy wiper reg to NV reg */

#define MAX5481_COPY_AB_TO_NV (2 << 4)

/* copy NV reg to wiper reg */

#define MAX5481_COPY_NV_TO_AB (3 << 4)

​

#define MAX5481_MAX_POS    1023

​

enum max5481_variant {

    max5481,

    max5482,

    max5483,

    max5484,

};

​

struct max5481_cfg {

    int kohms;

};

​

static const struct max5481_cfg max5481_cfg[] = {

    [max5481] = { .kohms =  10, },

    [max5482] = { .kohms =  50, },

    [max5483] = { .kohms =  10, },

    [max5484] = { .kohms =  50, },

};

​

struct max5481_data {

    struct spi_device *spi;

    const struct max5481_cfg *cfg;

    u8 msg[3] ____cacheline_aligned;

};

​

#define MAX5481_CHANNEL {                   \

    .type = IIO_RESISTANCE,                 \

    .indexed = 1,                       \

    .output = 1,                        \

    .channel = 0,                       \

    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),       \

    .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \

}

​

static const struct iio_chan_spec max5481_channels[] = {

    MAX5481_CHANNEL,

};

​

static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val)

{

    struct spi_device *spi = data->spi;

​

    data->msg[0] = cmd;

​

    switch (cmd) {

    case MAX5481_WRITE_WIPER:

        data->msg[1] = val >> 2;

        data->msg[2] = (val & 0x3) << 6;

        return spi_write(spi, data->msg, 3);

​

    case MAX5481_COPY_AB_TO_NV:

    case MAX5481_COPY_NV_TO_AB:

        return spi_write(spi, data->msg, 1);

​

    default:

        return -EIO;

    }

}

​

static int max5481_read_raw(struct iio_dev *indio_dev,

        struct iio_chan_spec const *chan,

        int *val, int *val2, long mask)

{