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         .id             = I2C_DRIVERID_PCF8574,
  71         .attach_adapter = pcf8574_attach_adapter,
  72         .detach_client  = pcf8574_detach_client,
  73 };
  74
  75 /* following are the sysfs callback functions */
  76 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  77 {
  78         struct i2c_client *client = to_i2c_client(dev);
  79         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  80 }
  81
  82 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  83
  84 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  85 {
  86         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  87
  88         if (data->write < 0)
  89                 return data->write;
  90
  91         return sprintf(buf, "%d\n", data->write);
  92 }
  93
  94 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  95                          size_t count)
  96 {
  97         struct i2c_client *client = to_i2c_client(dev);
  98         struct pcf8574_data *data = i2c_get_clientdata(client);
  99         unsigned long val = simple_strtoul(buf, NULL, 10);
 100
 101         if (val > 0xff)
 102                 return -EINVAL;
 103
 104         data->write = val;
 105         i2c_smbus_write_byte(client, data->write);
 106         return count;
 107 }
 108
 109 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 110
 111 static struct attribute *pcf8574_attributes[] = {
 112         &dev_attr_read.attr,
 113         &dev_attr_write.attr,
 114         NULL
 115 };
 116
 117 static const struct attribute_group pcf8574_attr_group = {
 118         .attrs = pcf8574_attributes,
 119 };
 120
 121 /*
 122  * Real code
 123  */
 124
 125 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 126 {
 127         return i2c_probe(adapter, &addr_data, pcf8574_detect);
 128 }
 129
 130 /* This function is called by i2c_probe */
 131 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 132 {
 133         struct i2c_client *new_client;
 134         struct pcf8574_data *data;
 135         int err = 0;
 136         const char *client_name = "";
 137
 138         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 139                 goto exit;
 140
 141         /* OK. For now, we presume we have a valid client. We now create the
 142            client structure, even though we cannot fill it completely yet. */
 143         if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 144                 err = -ENOMEM;
 145                 goto exit;
 146         }
 147
 148         new_client = &data->client;
 149         i2c_set_clientdata(new_client, data);
 150         new_client->addr = address;
 151         new_client->adapter = adapter;
 152         new_client->driver = &pcf8574_driver;
 153         new_client->flags = 0;
 154
 155         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 156            impossible to detect! Stupid chip. */
 157
 158         /* Determine the chip type */
 159         if (kind <= 0) {
 160                 if (address >= 0x38 && address <= 0x3f)
 161                         kind = pcf8574a;
 162                 else
 163                         kind = pcf8574;
 164         }
 165
 166         if (kind == pcf8574a)
 167                 client_name = "pcf8574a";
 168         else
 169                 client_name = "pcf8574";
 170
 171         /* Fill in the remaining client fields and put it into the global list */
 172         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 173
 174         /* Tell the I2C layer a new client has arrived */
 175         if ((err = i2c_attach_client(new_client)))
 176                 goto exit_free;
 177
 178         /* Initialize the PCF8574 chip */
 179         pcf8574_init_client(new_client);
 180
 181         /* Register sysfs hooks */
 182         err = sysfs_create_group(&new_client->dev.kobj, &pcf8574_attr_group);
 183         if (err)
 184                 goto exit_detach;
 185         return 0;
 186
 187       exit_detach:
 188         i2c_detach_client(new_client);
 189       exit_free:
 190         kfree(data);
 191       exit:
 192         return err;
 193 }
 194
 195 static int pcf8574_detach_client(struct i2c_client *client)
 196 {
 197         int err;
 198
 199         sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
 200
 201         if ((err = i2c_detach_client(client)))
 202                 return err;
 203
 204         kfree(i2c_get_clientdata(client));
 205         return 0;
 206 }
 207
 208 /* Called when we have found a new PCF8574. */
 209 static void pcf8574_init_client(struct i2c_client *client)
 210 {
 211         struct pcf8574_data *data = i2c_get_clientdata(client);
 212         data->write = -EAGAIN;
 213 }
 214
 215 static int __init pcf8574_init(void)
 216 {
 217         return i2c_add_driver(&pcf8574_driver);
 218 }
 219
 220 static void __exit pcf8574_exit(void)
 221 {
 222         i2c_del_driver(&pcf8574_driver);
 223 }
 224
 225
 226 MODULE_AUTHOR
 227     ("Frodo Looijaard <frodol@dds.nl>, "
 228      "Philip Edelbrock <phil@netroedge.com>, "
 229      "Dan Eaton <dan.eaton@rocketlogix.com> "
 230      "and Aurelien Jarno <aurelien@aurel32.net>");
 231 MODULE_DESCRIPTION("PCF8574 driver");
 232 MODULE_LICENSE("GPL");
 233
 234 module_init(pcf8574_init);
 235 module_exit(pcf8574_exit);