linux-imx

/*

 * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers

 *

 * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>

 *

 * 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/module.h>

#include <linux/spi/spi.h>

#include <linux/acpi.h>

​

#include <linux/iio/sysfs.h>

#include <linux/iio/iio.h>

​

#define MAX5487_WRITE_WIPER_A   (0x01 << 8)

#define MAX5487_WRITE_WIPER_B   (0x02 << 8)

​

/* copy both wiper regs to NV regs */

#define MAX5487_COPY_AB_TO_NV   (0x23 << 8)

/* copy both NV regs to wiper regs */

#define MAX5487_COPY_NV_TO_AB   (0x33 << 8)

​

#define MAX5487_MAX_POS     255

​

struct max5487_data {

    struct spi_device *spi;

    int kohms;

};

​

#define MAX5487_CHANNEL(ch, addr) {             \

    .type = IIO_RESISTANCE,                 \

    .indexed = 1,                       \

    .output = 1,                        \

    .channel = ch,                      \

    .address = addr,                    \

    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),       \

    .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \

}

​

static const struct iio_chan_spec max5487_channels[] = {

    MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),

    MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),

};

​

static int max5487_write_cmd(struct spi_device *spi, u16 cmd)

{

    return spi_write(spi, (const void *) &cmd, sizeof(u16));

}

​

static int max5487_read_raw(struct iio_dev *indio_dev,

                struct iio_chan_spec const *chan,

                int *val, int *val2, long mask)

{

    struct max5487_data *data = iio_priv(indio_dev);

​

    if (mask != IIO_CHAN_INFO_SCALE)

        return -EINVAL;

​

    *val = 1000 * data->kohms;

    *val2 = MAX5487_MAX_POS;