drivers/iio/dac/stx104.c

   1 /*
   2  * DAC driver for the Apex Embedded Systems STX104
   3  * Copyright (C) 2016 William Breathitt Gray
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  */
  14 #include <linux/bitops.h>
  15 #include <linux/device.h>
  16 #include <linux/errno.h>
  17 #include <linux/iio/iio.h>
  18 #include <linux/iio/types.h>
  19 #include <linux/io.h>
  20 #include <linux/ioport.h>
  21 #include <linux/isa.h>
  22 #include <linux/module.h>
  23 #include <linux/moduleparam.h>
  24
  25 #define STX104_NUM_CHAN 2
  26
  27 #define STX104_CHAN(chan) {                             \
  28         .type = IIO_VOLTAGE,                            \
  29         .channel = chan,                                \
  30         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),   \
  31         .indexed = 1,                                   \
  32         .output = 1                                     \
  33 }
  34
  35 #define STX104_EXTENT 16
  36 /**
  37  * The highest base address possible for an ISA device is 0x3FF; this results in
  38  * 1024 possible base addresses. Dividing the number of possible base addresses
  39  * by the address extent taken by each device results in the maximum number of
  40  * devices on a system.
  41  */
  42 #define MAX_NUM_STX104 (1024 / STX104_EXTENT)
  43
  44 static unsigned base[MAX_NUM_STX104];
  45 static unsigned num_stx104;
  46 module_param_array(base, uint, &num_stx104, 0);
  47 MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");
  48
  49 /**
  50  * struct stx104_iio - IIO device private data structure
  51  * @chan_out_states:    channels' output states
  52  * @base:               base port address of the IIO device
  53  */
  54 struct stx104_iio {
  55         unsigned chan_out_states[STX104_NUM_CHAN];
  56         unsigned base;
  57 };
  58
  59 static int stx104_read_raw(struct iio_dev *indio_dev,
  60         struct iio_chan_spec const *chan, int *val, int *val2, long mask)
  61 {
  62         struct stx104_iio *const priv = iio_priv(indio_dev);
  63
  64         if (mask != IIO_CHAN_INFO_RAW)
  65                 return -EINVAL;
  66
  67         *val = priv->chan_out_states[chan->channel];
  68
  69         return IIO_VAL_INT;
  70 }
  71
  72 static int stx104_write_raw(struct iio_dev *indio_dev,
  73         struct iio_chan_spec const *chan, int val, int val2, long mask)
  74 {
  75         struct stx104_iio *const priv = iio_priv(indio_dev);
  76         const unsigned chan_addr_offset = 2 * chan->channel;
  77
  78         if (mask != IIO_CHAN_INFO_RAW)
  79                 return -EINVAL;
  80
  81         priv->chan_out_states[chan->channel] = val;
  82         outw(val, priv->base + 4 + chan_addr_offset);
  83
  84         return 0;
  85 }
  86
  87 static const struct iio_info stx104_info = {
  88         .driver_module = THIS_MODULE,
  89         .read_raw = stx104_read_raw,
  90         .write_raw = stx104_write_raw
  91 };
  92
  93 static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
  94         STX104_CHAN(0),
  95         STX104_CHAN(1)
  96 };
  97
  98 static int stx104_probe(struct device *dev, unsigned int id)
  99 {
 100         struct iio_dev *indio_dev;
 101         struct stx104_iio *priv;
 102
 103         indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
 104         if (!indio_dev)
 105                 return -ENOMEM;
 106
 107         if (!devm_request_region(dev, base[id], STX104_EXTENT,
 108                 dev_name(dev))) {
 109                 dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
 110                         base[id], base[id] + STX104_EXTENT);
 111                 return -EBUSY;
 112         }
 113
 114         indio_dev->info = &stx104_info;
 115         indio_dev->modes = INDIO_DIRECT_MODE;
 116         indio_dev->channels = stx104_channels;
 117         indio_dev->num_channels = STX104_NUM_CHAN;
 118         indio_dev->name = dev_name(dev);
 119
 120         priv = iio_priv(indio_dev);
 121         priv->base = base[id];
 122
 123         /* initialize DAC output to 0V */
 124         outw(0, base[id] + 4);
 125         outw(0, base[id] + 6);
 126
 127         return devm_iio_device_register(dev, indio_dev);
 128 }
 129
 130 static struct isa_driver stx104_driver = {
 131         .probe = stx104_probe,
 132         .driver = {
 133                 .name = "stx104"
 134         }
 135 };
 136
 137 static void __exit stx104_exit(void)
 138 {
 139         isa_unregister_driver(&stx104_driver);
 140 }
 141
 142 static int __init stx104_init(void)
 143 {
 144         return isa_register_driver(&stx104_driver, num_stx104);
 145 }
 146
 147 module_init(stx104_init);
 148 module_exit(stx104_exit);
 149
 150 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
 151 MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
 152 MODULE_LICENSE("GPL v2");