drivers/i2c/chips/pcf8574.c

   1 /*
   2     Copyright (c) 2000  Frodo Looijaard <frodol@dds.nl>,
   3                         Philip Edelbrock <phil@netroedge.com>,
   4                         Dan Eaton <dan.eaton@rocketlogix.com>
   5     Ported to Linux 2.6 by Aurelien Jarno <aurel32@debian.org> with
   6     the help of Jean Delvare <khali@linux-fr.org>
   7
   8     This program is free software; you can redistribute it and/or modify
   9     it under the terms of the GNU General Public License as published by
  10     the Free Software Foundation; either version 2 of the License, or
  11     (at your option) any later version.
  12
  13     This program is distributed in the hope that it will be useful,
  14     but WITHOUT ANY WARRANTY; without even the implied warranty of
  15     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16     GNU General Public License for more details.
  17
  18     You should have received a copy of the GNU General Public License
  19     along with this program; if not, write to the Free Software
  20     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 /* A few notes about the PCF8574:
  24
  25 * The PCF8574 is an 8-bit I/O expander for the I2C bus produced by
  26   Philips Semiconductors.  It is designed to provide a byte I2C
  27   interface to up to 8 separate devices.
  28
  29 * The PCF8574 appears as a very simple SMBus device which can be
  30   read from or written to with SMBUS byte read/write accesses.
  31
  32   --Dan
  33
  34 */
  35
  36 #include <linux/module.h>
  37 #include <linux/init.h>
  38 #include <linux/slab.h>
  39 #include <linux/i2c.h>
  40
  41 /* Addresses to scan: none, device can't be detected */
  42 static const unsigned short normal_i2c[] = { I2C_CLIENT_END };
  43
  44 /* Insmod parameters */
  45 I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);
  46
  47 /* Each client has this additional data */
  48 struct pcf8574_data {
  49         int write;                      /* Remember last written value */
  50 };
  51
  52 static void pcf8574_init_client(struct i2c_client *client);
  53
  54 /* following are the sysfs callback functions */
  55 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  56 {
  57         struct i2c_client *client = to_i2c_client(dev);
  58         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  59 }
  60
  61 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  62
  63 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  64 {
  65         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  66
  67         if (data->write < 0)
  68                 return data->write;
  69
  70         return sprintf(buf, "%d\n", data->write);
  71 }
  72
  73 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  74                          size_t count)
  75 {
  76         struct i2c_client *client = to_i2c_client(dev);
  77         struct pcf8574_data *data = i2c_get_clientdata(client);
  78         unsigned long val = simple_strtoul(buf, NULL, 10);
  79
  80         if (val > 0xff)
  81                 return -EINVAL;
  82
  83         data->write = val;
  84         i2c_smbus_write_byte(client, data->write);
  85         return count;
  86 }
  87
  88 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
  89
  90 static struct attribute *pcf8574_attributes[] = {
  91         &dev_attr_read.attr,
  92         &dev_attr_write.attr,
  93         NULL
  94 };
  95
  96 static const struct attribute_group pcf8574_attr_group = {
  97         .attrs = pcf8574_attributes,
  98 };
  99
 100 /*
 101  * Real code
 102  */
 103
 104 /* Return 0 if detection is successful, -ENODEV otherwise */
 105 static int pcf8574_detect(struct i2c_client *client, int kind,
 106                           struct i2c_board_info *info)
 107 {
 108         struct i2c_adapter *adapter = client->adapter;
 109         const char *client_name;
 110
 111         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 112                 return -ENODEV;
 113
 114         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 115            impossible to detect! Stupid chip. */
 116
 117         /* Determine the chip type */
 118         if (kind <= 0) {
 119                 if (client->addr >= 0x38 && client->addr <= 0x3f)
 120                         kind = pcf8574a;
 121                 else
 122                         kind = pcf8574;
 123         }
 124
 125         if (kind == pcf8574a)
 126                 client_name = "pcf8574a";
 127         else
 128                 client_name = "pcf8574";
 129         strlcpy(info->type, client_name, I2C_NAME_SIZE);
 130
 131         return 0;
 132 }
 133
 134 static int pcf8574_probe(struct i2c_client *client,
 135                          const struct i2c_device_id *id)
 136 {
 137         struct pcf8574_data *data;
 138         int err;
 139
 140         data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL);
 141         if (!data) {
 142                 err = -ENOMEM;
 143                 goto exit;
 144         }
 145
 146         i2c_set_clientdata(client, data);
 147
 148         /* Initialize the PCF8574 chip */
 149         pcf8574_init_client(client);
 150
 151         /* Register sysfs hooks */
 152         err = sysfs_create_group(&client->dev.kobj, &pcf8574_attr_group);
 153         if (err)
 154                 goto exit_free;
 155         return 0;
 156
 157       exit_free:
 158         kfree(data);
 159       exit:
 160         return err;
 161 }
 162
 163 static int pcf8574_remove(struct i2c_client *client)
 164 {
 165         sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
 166         kfree(i2c_get_clientdata(client));
 167         return 0;
 168 }
 169
 170 /* Called when we have found a new PCF8574. */
 171 static void pcf8574_init_client(struct i2c_client *client)
 172 {
 173         struct pcf8574_data *data = i2c_get_clientdata(client);
 174         data->write = -EAGAIN;
 175 }
 176
 177 static const struct i2c_device_id pcf8574_id[] = {
 178         { "pcf8574", 0 },
 179         { "pcf8574a", 0 },
 180         { }
 181 };
 182
 183 static struct i2c_driver pcf8574_driver = {
 184         .driver = {
 185                 .name   = "pcf8574",
 186         },
 187         .probe          = pcf8574_probe,
 188         .remove         = pcf8574_remove,
 189         .id_table       = pcf8574_id,
 190
 191         .detect         = pcf8574_detect,
 192         .address_data   = &addr_data,
 193 };
 194
 195 static int __init pcf8574_init(void)
 196 {
 197         return i2c_add_driver(&pcf8574_driver);
 198 }
 199
 200 static void __exit pcf8574_exit(void)
 201 {
 202         i2c_del_driver(&pcf8574_driver);
 203 }
 204
 205
 206 MODULE_AUTHOR
 207     ("Frodo Looijaard <frodol@dds.nl>, "
 208      "Philip Edelbrock <phil@netroedge.com>, "
 209      "Dan Eaton <dan.eaton@rocketlogix.com> "
 210      "and Aurelien Jarno <aurelien@aurel32.net>");
 211 MODULE_DESCRIPTION("PCF8574 driver");
 212 MODULE_LICENSE("GPL");
 213
 214 module_init(pcf8574_init);
 215 module_exit(pcf8574_exit);