drivers/i2c/chips/pcf8574.c

   1 /*
   2     pcf8574.c - Part of lm_sensors, Linux kernel modules for hardware
   3              monitoring
   4     Copyright (c) 2000  Frodo Looijaard <frodol@dds.nl>,
   5                         Philip Edelbrock <phil@netroedge.com>,
   6                         Dan Eaton <dan.eaton@rocketlogix.com>
   7     Ported to Linux 2.6 by Aurelien Jarno <aurel32@debian.org> with
   8     the help of Jean Delvare <khali@linux-fr.org>
   9
  10     This program is free software; you can redistribute it and/or modify
  11     it under the terms of the GNU General Public License as published by
  12     the Free Software Foundation; either version 2 of the License, or
  13     (at your option) any later version.
  14
  15     This program is distributed in the hope that it will be useful,
  16     but WITHOUT ANY WARRANTY; without even the implied warranty of
  17     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18     GNU General Public License for more details.
  19
  20     You should have received a copy of the GNU General Public License
  21     along with this program; if not, write to the Free Software
  22     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23 */
  24
  25 /* A few notes about the PCF8574:
  26
  27 * The PCF8574 is an 8-bit I/O expander for the I2C bus produced by
  28   Philips Semiconductors.  It is designed to provide a byte I2C
  29   interface to up to 8 separate devices.
  30
  31 * The PCF8574 appears as a very simple SMBus device which can be
  32   read from or written to with SMBUS byte read/write accesses.
  33
  34   --Dan
  35
  36 */
  37
  38 #include <linux/module.h>
  39 #include <linux/init.h>
  40 #include <linux/slab.h>
  41 #include <linux/i2c.h>
  42
  43 /* Addresses to scan */
  44 static const unsigned short normal_i2c[] = {
  45         0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
  46         0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
  47         I2C_CLIENT_END
  48 };
  49
  50 /* Insmod parameters */
  51 I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);
  52
  53 /* Each client has this additional data */
  54 struct pcf8574_data {
  55         struct i2c_client client;
  56
  57         int write;                      /* Remember last written value */
  58 };
  59
  60 static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
  61 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
  62 static int pcf8574_detach_client(struct i2c_client *client);
  63 static void pcf8574_init_client(struct i2c_client *client);
  64
  65 /* This is the driver that will be inserted */
  66 static struct i2c_driver pcf8574_driver = {
  67         .driver = {
  68                 .name   = "pcf8574",
  69         },
  70         .attach_adapter = pcf8574_attach_adapter,
  71         .detach_client  = pcf8574_detach_client,
  72 };
  73
  74 /* following are the sysfs callback functions */
  75 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  76 {
  77         struct i2c_client *client = to_i2c_client(dev);
  78         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  79 }
  80
  81 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  82
  83 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  84 {
  85         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  86
  87         if (data->write < 0)
  88                 return data->write;
  89
  90         return sprintf(buf, "%d\n", data->write);
  91 }
  92
  93 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  94                          size_t count)
  95 {
  96         struct i2c_client *client = to_i2c_client(dev);
  97         struct pcf8574_data *data = i2c_get_clientdata(client);
  98         unsigned long val = simple_strtoul(buf, NULL, 10);
  99
 100         if (val > 0xff)
 101                 return -EINVAL;
 102
 103         data->write = val;
 104         i2c_smbus_write_byte(client, data->write);
 105         return count;
 106 }
 107
 108 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 109
 110 static struct attribute *pcf8574_attributes[] = {
 111         &dev_attr_read.attr,
 112         &dev_attr_write.attr,
 113         NULL
 114 };
 115
 116 static const struct attribute_group pcf8574_attr_group = {
 117         .attrs = pcf8574_attributes,
 118 };
 119
 120 /*
 121  * Real code
 122  */
 123
 124 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 125 {
 126         return i2c_probe(adapter, &addr_data, pcf8574_detect);
 127 }
 128
 129 /* This function is called by i2c_probe */
 130 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 131 {
 132         struct i2c_client *new_client;
 133         struct pcf8574_data *data;
 134         int err = 0;
 135         const char *client_name = "";
 136
 137         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 138                 goto exit;
 139
 140         /* OK. For now, we presume we have a valid client. We now create the
 141            client structure, even though we cannot fill it completely yet. */
 142         if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 143                 err = -ENOMEM;
 144                 goto exit;
 145         }
 146
 147         new_client = &data->client;
 148         i2c_set_clientdata(new_client, data);
 149         new_client->addr = address;
 150         new_client->adapter = adapter;
 151         new_client->driver = &pcf8574_driver;
 152         new_client->flags = 0;
 153
 154         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 155            impossible to detect! Stupid chip. */
 156
 157         /* Determine the chip type */
 158         if (kind <= 0) {
 159                 if (address >= 0x38 && address <= 0x3f)
 160                         kind = pcf8574a;
 161                 else
 162                         kind = pcf8574;
 163         }
 164
 165         if (kind == pcf8574a)
 166                 client_name = "pcf8574a";
 167         else
 168                 client_name = "pcf8574";
 169
 170         /* Fill in the remaining client fields and put it into the global list */
 171         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 172
 173         /* Tell the I2C layer a new client has arrived */
 174         if ((err = i2c_attach_client(new_client)))
 175                 goto exit_free;
 176
 177         /* Initialize the PCF8574 chip */
 178         pcf8574_init_client(new_client);
 179
 180         /* Register sysfs hooks */
 181         err = sysfs_create_group(&new_client->dev.kobj, &pcf8574_attr_group);
 182         if (err)
 183                 goto exit_detach;
 184         return 0;
 185
 186       exit_detach:
 187         i2c_detach_client(new_client);
 188       exit_free:
 189         kfree(data);
 190       exit:
 191         return err;
 192 }
 193
 194 static int pcf8574_detach_client(struct i2c_client *client)
 195 {
 196         int err;
 197
 198         sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
 199
 200         if ((err = i2c_detach_client(client)))
 201                 return err;
 202
 203         kfree(i2c_get_clientdata(client));
 204         return 0;
 205 }
 206
 207 /* Called when we have found a new PCF8574. */
 208 static void pcf8574_init_client(struct i2c_client *client)
 209 {
 210         struct pcf8574_data *data = i2c_get_clientdata(client);
 211         data->write = -EAGAIN;
 212 }
 213
 214 static int __init pcf8574_init(void)
 215 {
 216         return i2c_add_driver(&pcf8574_driver);
 217 }
 218
 219 static void __exit pcf8574_exit(void)
 220 {
 221         i2c_del_driver(&pcf8574_driver);
 222 }
 223
 224
 225 MODULE_AUTHOR
 226     ("Frodo Looijaard <frodol@dds.nl>, "
 227      "Philip Edelbrock <phil@netroedge.com>, "
 228      "Dan Eaton <dan.eaton@rocketlogix.com> "
 229      "and Aurelien Jarno <aurelien@aurel32.net>");
 230 MODULE_DESCRIPTION("PCF8574 driver");
 231 MODULE_LICENSE("GPL");
 232
 233 module_init(pcf8574_init);
 234 module_exit(pcf8574_exit);