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 */
  42 static const unsigned short normal_i2c[] = {
  43         0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
  44         0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
  45         I2C_CLIENT_END
  46 };
  47
  48 /* Insmod parameters */
  49 I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);
  50
  51 /* Each client has this additional data */
  52 struct pcf8574_data {
  53         struct i2c_client client;
  54
  55         int write;                      /* Remember last written value */
  56 };
  57
  58 static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
  59 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
  60 static int pcf8574_detach_client(struct i2c_client *client);
  61 static void pcf8574_init_client(struct i2c_client *client);
  62
  63 /* This is the driver that will be inserted */
  64 static struct i2c_driver pcf8574_driver = {
  65         .driver = {
  66                 .name   = "pcf8574",
  67         },
  68         .attach_adapter = pcf8574_attach_adapter,
  69         .detach_client  = pcf8574_detach_client,
  70 };
  71
  72 /* following are the sysfs callback functions */
  73 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  74 {
  75         struct i2c_client *client = to_i2c_client(dev);
  76         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  77 }
  78
  79 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  80
  81 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  82 {
  83         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  84
  85         if (data->write < 0)
  86                 return data->write;
  87
  88         return sprintf(buf, "%d\n", data->write);
  89 }
  90
  91 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  92                          size_t count)
  93 {
  94         struct i2c_client *client = to_i2c_client(dev);
  95         struct pcf8574_data *data = i2c_get_clientdata(client);
  96         unsigned long val = simple_strtoul(buf, NULL, 10);
  97
  98         if (val > 0xff)
  99                 return -EINVAL;
 100
 101         data->write = val;
 102         i2c_smbus_write_byte(client, data->write);
 103         return count;
 104 }
 105
 106 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 107
 108 static struct attribute *pcf8574_attributes[] = {
 109         &dev_attr_read.attr,
 110         &dev_attr_write.attr,
 111         NULL
 112 };
 113
 114 static const struct attribute_group pcf8574_attr_group = {
 115         .attrs = pcf8574_attributes,
 116 };
 117
 118 /*
 119  * Real code
 120  */
 121
 122 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 123 {
 124         return i2c_probe(adapter, &addr_data, pcf8574_detect);
 125 }
 126
 127 /* This function is called by i2c_probe */
 128 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 129 {
 130         struct i2c_client *client;
 131         struct pcf8574_data *data;
 132         int err = 0;
 133         const char *client_name = "";
 134
 135         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 136                 goto exit;
 137
 138         /* OK. For now, we presume we have a valid client. We now create the
 139            client structure, even though we cannot fill it completely yet. */
 140         if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 141                 err = -ENOMEM;
 142                 goto exit;
 143         }
 144
 145         client = &data->client;
 146         i2c_set_clientdata(client, data);
 147         client->addr = address;
 148         client->adapter = adapter;
 149         client->driver = &pcf8574_driver;
 150
 151         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 152            impossible to detect! Stupid chip. */
 153
 154         /* Determine the chip type */
 155         if (kind <= 0) {
 156                 if (address >= 0x38 && address <= 0x3f)
 157                         kind = pcf8574a;
 158                 else
 159                         kind = pcf8574;
 160         }
 161
 162         if (kind == pcf8574a)
 163                 client_name = "pcf8574a";
 164         else
 165                 client_name = "pcf8574";
 166
 167         /* Fill in the remaining client fields and put it into the global list */
 168         strlcpy(client->name, client_name, I2C_NAME_SIZE);
 169
 170         /* Tell the I2C layer a new client has arrived */
 171         if ((err = i2c_attach_client(client)))
 172                 goto exit_free;
 173
 174         /* Initialize the PCF8574 chip */
 175         pcf8574_init_client(client);
 176
 177         /* Register sysfs hooks */
 178         err = sysfs_create_group(&client->dev.kobj, &pcf8574_attr_group);
 179         if (err)
 180                 goto exit_detach;
 181         return 0;
 182
 183       exit_detach:
 184         i2c_detach_client(client);
 185       exit_free:
 186         kfree(data);
 187       exit:
 188         return err;
 189 }
 190
 191 static int pcf8574_detach_client(struct i2c_client *client)
 192 {
 193         int err;
 194
 195         sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
 196
 197         if ((err = i2c_detach_client(client)))
 198                 return err;
 199
 200         kfree(i2c_get_clientdata(client));
 201         return 0;
 202 }
 203
 204 /* Called when we have found a new PCF8574. */
 205 static void pcf8574_init_client(struct i2c_client *client)
 206 {
 207         struct pcf8574_data *data = i2c_get_clientdata(client);
 208         data->write = -EAGAIN;
 209 }
 210
 211 static int __init pcf8574_init(void)
 212 {
 213         return i2c_add_driver(&pcf8574_driver);
 214 }
 215
 216 static void __exit pcf8574_exit(void)
 217 {
 218         i2c_del_driver(&pcf8574_driver);
 219 }
 220
 221
 222 MODULE_AUTHOR
 223     ("Frodo Looijaard <frodol@dds.nl>, "
 224      "Philip Edelbrock <phil@netroedge.com>, "
 225      "Dan Eaton <dan.eaton@rocketlogix.com> "
 226      "and Aurelien Jarno <aurelien@aurel32.net>");
 227 MODULE_DESCRIPTION("PCF8574 driver");
 228 MODULE_LICENSE("GPL");
 229
 230 module_init(pcf8574_init);
 231 module_exit(pcf8574_exit);