drivers/iio/chemical/vz89x.c

   1 /*
   2  * vz89x.c - Support for SGX Sensortech MiCS VZ89X VOC sensors
   3  *
   4  * Copyright (C) 2015 Matt Ranostay <mranostay@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 as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  */
  17
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20 #include <linux/init.h>
  21 #include <linux/i2c.h>
  22
  23 #include <linux/iio/iio.h>
  24 #include <linux/iio/sysfs.h>
  25
  26 #define VZ89X_REG_MEASUREMENT           0x09
  27 #define VZ89X_REG_MEASUREMENT_SIZE      6
  28
  29 #define VZ89X_VOC_CO2_IDX               0
  30 #define VZ89X_VOC_SHORT_IDX             1
  31 #define VZ89X_VOC_TVOC_IDX              2
  32 #define VZ89X_VOC_RESISTANCE_IDX        3
  33
  34 struct vz89x_data {
  35         struct i2c_client *client;
  36         struct mutex lock;
  37         unsigned long last_update;
  38
  39         u8 buffer[VZ89X_REG_MEASUREMENT_SIZE];
  40 };
  41
  42 static const struct iio_chan_spec vz89x_channels[] = {
  43         {
  44                 .type = IIO_CONCENTRATION,
  45                 .channel2 = IIO_MOD_CO2,
  46                 .modified = 1,
  47                 .info_mask_separate =
  48                         BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
  49                 .address = VZ89X_VOC_CO2_IDX,
  50         },
  51         {
  52                 .type = IIO_CONCENTRATION,
  53                 .channel2 = IIO_MOD_VOC,
  54                 .modified = 1,
  55                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
  56                 .address = VZ89X_VOC_SHORT_IDX,
  57                 .extend_name = "short",
  58         },
  59         {
  60                 .type = IIO_CONCENTRATION,
  61                 .channel2 = IIO_MOD_VOC,
  62                 .modified = 1,
  63                 .info_mask_separate =
  64                         BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
  65                 .address = VZ89X_VOC_TVOC_IDX,
  66         },
  67         {
  68                 .type = IIO_RESISTANCE,
  69                 .info_mask_separate =
  70                         BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
  71                 .address = VZ89X_VOC_RESISTANCE_IDX,
  72         },
  73 };
  74
  75 static IIO_CONST_ATTR(in_concentration_co2_scale, "0.00000698689");
  76 static IIO_CONST_ATTR(in_concentration_voc_scale, "0.00000000436681223");
  77
  78 static struct attribute *vz89x_attributes[] = {
  79         &iio_const_attr_in_concentration_co2_scale.dev_attr.attr,
  80         &iio_const_attr_in_concentration_voc_scale.dev_attr.attr,
  81         NULL,
  82 };
  83
  84 static const struct attribute_group vz89x_attrs_group = {
  85         .attrs = vz89x_attributes,
  86 };
  87
  88 /*
  89  * Chipset sometime updates in the middle of a reading causing it to reset the
  90  * data pointer, and causing invalid reading of previous data.
  91  * We can check for this by reading MSB of the resistance reading that is
  92  * always zero, and by also confirming the VOC_short isn't zero.
  93  */
  94
  95 static int vz89x_measurement_is_valid(struct vz89x_data *data)
  96 {
  97         if (data->buffer[VZ89X_VOC_SHORT_IDX] == 0)
  98                 return 1;
  99
 100         return !!(data->buffer[VZ89X_REG_MEASUREMENT_SIZE - 1] > 0);
 101 }
 102
 103 static int vz89x_get_measurement(struct vz89x_data *data)
 104 {
 105         int ret;
 106         int i;
 107
 108         /* sensor can only be polled once a second max per datasheet */
 109         if (!time_after(jiffies, data->last_update + HZ))
 110                 return 0;
 111
 112         ret = i2c_smbus_write_word_data(data->client,
 113                                         VZ89X_REG_MEASUREMENT, 0);
 114         if (ret < 0)
 115                 return ret;
 116
 117         for (i = 0; i < VZ89X_REG_MEASUREMENT_SIZE; i++) {
 118                 ret = i2c_smbus_read_byte(data->client);
 119                 if (ret < 0)
 120                         return ret;
 121                 data->buffer[i] = ret;
 122         }
 123
 124         ret = vz89x_measurement_is_valid(data);
 125         if (ret)
 126                 return -EAGAIN;
 127
 128         data->last_update = jiffies;
 129
 130         return 0;
 131 }
 132
 133 static int vz89x_get_resistance_reading(struct vz89x_data *data)
 134 {
 135         u8 *buf = &data->buffer[VZ89X_VOC_RESISTANCE_IDX];
 136
 137         return buf[0] | (buf[1] << 8);
 138 }
 139
 140 static int vz89x_read_raw(struct iio_dev *indio_dev,
 141                           struct iio_chan_spec const *chan, int *val,
 142                           int *val2, long mask)
 143 {
 144         struct vz89x_data *data = iio_priv(indio_dev);
 145         int ret = -EINVAL;
 146
 147         switch (mask) {
 148         case IIO_CHAN_INFO_RAW:
 149                 mutex_lock(&data->lock);
 150                 ret = vz89x_get_measurement(data);
 151                 mutex_unlock(&data->lock);
 152
 153                 if (ret)
 154                         return ret;
 155
 156                 switch (chan->address) {
 157                 case VZ89X_VOC_CO2_IDX:
 158                 case VZ89X_VOC_SHORT_IDX:
 159                 case VZ89X_VOC_TVOC_IDX:
 160                         *val = data->buffer[chan->address];
 161                         return IIO_VAL_INT;
 162                 case VZ89X_VOC_RESISTANCE_IDX:
 163                         *val = vz89x_get_resistance_reading(data);
 164                         return IIO_VAL_INT;
 165                 default:
 166                         return -EINVAL;
 167                 }
 168                 break;
 169         case IIO_CHAN_INFO_SCALE:
 170                 switch (chan->type) {
 171                 case IIO_RESISTANCE:
 172                         *val = 10;
 173                         return IIO_VAL_INT;
 174                 default:
 175                         return -EINVAL;
 176                 }
 177                 break;
 178         case IIO_CHAN_INFO_OFFSET:
 179                 switch (chan->address) {
 180                 case VZ89X_VOC_CO2_IDX:
 181                         *val = 44;
 182                         *val2 = 250000;
 183                         return IIO_VAL_INT_PLUS_MICRO;
 184                 case VZ89X_VOC_TVOC_IDX:
 185                         *val = -13;
 186                         return IIO_VAL_INT;
 187                 default:
 188                         return -EINVAL;
 189                 }
 190         }
 191
 192         return ret;
 193 }
 194
 195 static const struct iio_info vz89x_info = {
 196         .attrs          = &vz89x_attrs_group,
 197         .read_raw       = vz89x_read_raw,
 198         .driver_module  = THIS_MODULE,
 199 };
 200
 201 static int vz89x_probe(struct i2c_client *client,
 202                        const struct i2c_device_id *id)
 203 {
 204         struct iio_dev *indio_dev;
 205         struct vz89x_data *data;
 206
 207         if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA |
 208                                      I2C_FUNC_SMBUS_BYTE))
 209                 return -ENODEV;
 210
 211         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 212         if (!indio_dev)
 213                 return -ENOMEM;
 214
 215         data = iio_priv(indio_dev);
 216         i2c_set_clientdata(client, indio_dev);
 217         data->client = client;
 218         data->last_update = jiffies - HZ;
 219         mutex_init(&data->lock);
 220
 221         indio_dev->dev.parent = &client->dev;
 222         indio_dev->info = &vz89x_info,
 223         indio_dev->name = dev_name(&client->dev);
 224         indio_dev->modes = INDIO_DIRECT_MODE;
 225
 226         indio_dev->channels = vz89x_channels;
 227         indio_dev->num_channels = ARRAY_SIZE(vz89x_channels);
 228
 229         return devm_iio_device_register(&client->dev, indio_dev);
 230 }
 231
 232 static const struct i2c_device_id vz89x_id[] = {
 233         { "vz89x", 0 },
 234         { }
 235 };
 236 MODULE_DEVICE_TABLE(i2c, vz89x_id);
 237
 238 static const struct of_device_id vz89x_dt_ids[] = {
 239         { .compatible = "sgx,vz89x" },
 240         { }
 241 };
 242 MODULE_DEVICE_TABLE(of, vz89x_dt_ids);
 243
 244 static struct i2c_driver vz89x_driver = {
 245         .driver = {
 246                 .name   = "vz89x",
 247                 .of_match_table = of_match_ptr(vz89x_dt_ids),
 248         },
 249         .probe = vz89x_probe,
 250         .id_table = vz89x_id,
 251 };
 252 module_i2c_driver(vz89x_driver);
 253
 254 MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
 255 MODULE_DESCRIPTION("SGX Sensortech MiCS VZ89X VOC sensors");
 256 MODULE_LICENSE("GPL v2");