drivers/iio/potentiometer/max5487.c

   1 /*
   2  * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
   3  *
   4  * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  */
  11 #include <linux/module.h>
  12 #include <linux/spi/spi.h>
  13 #include <linux/acpi.h>
  14
  15 #include <linux/iio/sysfs.h>
  16 #include <linux/iio/iio.h>
  17
  18 #define MAX5487_WRITE_WIPER_A   (0x01 << 8)
  19 #define MAX5487_WRITE_WIPER_B   (0x02 << 8)
  20
  21 /* copy both wiper regs to NV regs */
  22 #define MAX5487_COPY_AB_TO_NV   (0x23 << 8)
  23 /* copy both NV regs to wiper regs */
  24 #define MAX5487_COPY_NV_TO_AB   (0x33 << 8)
  25
  26 #define MAX5487_MAX_POS         255
  27
  28 struct max5487_data {
  29         struct spi_device *spi;
  30         int kohms;
  31 };
  32
  33 #define MAX5487_CHANNEL(ch, addr) {                             \
  34         .type = IIO_RESISTANCE,                                 \
  35         .indexed = 1,                                           \
  36         .output = 1,                                            \
  37         .channel = ch,                                          \
  38         .address = addr,                                        \
  39         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
  40         .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
  41 }
  42
  43 static const struct iio_chan_spec max5487_channels[] = {
  44         MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
  45         MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
  46 };
  47
  48 static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
  49 {
  50         return spi_write(spi, (const void *) &cmd, sizeof(u16));
  51 }
  52
  53 static int max5487_read_raw(struct iio_dev *indio_dev,
  54                             struct iio_chan_spec const *chan,
  55                             int *val, int *val2, long mask)
  56 {
  57         struct max5487_data *data = iio_priv(indio_dev);
  58
  59         if (mask != IIO_CHAN_INFO_SCALE)
  60                 return -EINVAL;
  61
  62         *val = 1000 * data->kohms;
  63         *val2 = MAX5487_MAX_POS;
  64
  65         return IIO_VAL_FRACTIONAL;
  66 }
  67
  68 static int max5487_write_raw(struct iio_dev *indio_dev,
  69                              struct iio_chan_spec const *chan,
  70                              int val, int val2, long mask)
  71 {
  72         struct max5487_data *data = iio_priv(indio_dev);
  73
  74         if (mask != IIO_CHAN_INFO_RAW)
  75                 return -EINVAL;
  76
  77         if (val < 0 || val > MAX5487_MAX_POS)
  78                 return -EINVAL;
  79
  80         return max5487_write_cmd(data->spi, chan->address | val);
  81 }
  82
  83 static const struct iio_info max5487_info = {
  84         .read_raw = max5487_read_raw,
  85         .write_raw = max5487_write_raw,
  86         .driver_module = THIS_MODULE,
  87 };
  88
  89 static int max5487_spi_probe(struct spi_device *spi)
  90 {
  91         struct iio_dev *indio_dev;
  92         struct max5487_data *data;
  93         const struct spi_device_id *id = spi_get_device_id(spi);
  94         int ret;
  95
  96         indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
  97         if (!indio_dev)
  98                 return -ENOMEM;
  99
 100         dev_set_drvdata(&spi->dev, indio_dev);
 101         data = iio_priv(indio_dev);
 102
 103         data->spi = spi;
 104         data->kohms = id->driver_data;
 105
 106         indio_dev->info = &max5487_info;
 107         indio_dev->name = id->name;
 108         indio_dev->dev.parent = &spi->dev;
 109         indio_dev->modes = INDIO_DIRECT_MODE;
 110         indio_dev->channels = max5487_channels;
 111         indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
 112
 113         /* restore both wiper regs from NV regs */
 114         ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
 115         if (ret < 0)
 116                 return ret;
 117
 118         return iio_device_register(indio_dev);
 119 }
 120
 121 static int max5487_spi_remove(struct spi_device *spi)
 122 {
 123         struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
 124
 125         iio_device_unregister(indio_dev);
 126
 127         /* save both wiper regs to NV regs */
 128         return max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
 129 }
 130
 131 static const struct spi_device_id max5487_id[] = {
 132         { "MAX5487", 10 },
 133         { "MAX5488", 50 },
 134         { "MAX5489", 100 },
 135         { }
 136 };
 137 MODULE_DEVICE_TABLE(spi, max5487_id);
 138
 139 static const struct acpi_device_id max5487_acpi_match[] = {
 140         { "MAX5487", 10 },
 141         { "MAX5488", 50 },
 142         { "MAX5489", 100 },
 143         { },
 144 };
 145 MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
 146
 147 static struct spi_driver max5487_driver = {
 148         .driver = {
 149                 .name = "max5487",
 150                 .owner = THIS_MODULE,
 151                 .acpi_match_table = ACPI_PTR(max5487_acpi_match),
 152         },
 153         .id_table = max5487_id,
 154         .probe = max5487_spi_probe,
 155         .remove = max5487_spi_remove
 156 };
 157 module_spi_driver(max5487_driver);
 158
 159 MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
 160 MODULE_DESCRIPTION("max5487 SPI driver");
 161 MODULE_LICENSE("GPL v2");