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 unsigned short normal_i2c[] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
  45                                         0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
  46                                         I2C_CLIENT_END };
  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         .id             = I2C_DRIVERID_PCF8574,
  69         .attach_adapter = pcf8574_attach_adapter,
  70         .detach_client  = pcf8574_detach_client,
  71 };
  72
  73 /* following are the sysfs callback functions */
  74 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  75 {
  76         struct i2c_client *client = to_i2c_client(dev);
  77         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  78 }
  79
  80 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  81
  82 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  83 {
  84         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  85
  86         if (data->write < 0)
  87                 return data->write;
  88
  89         return sprintf(buf, "%d\n", data->write);
  90 }
  91
  92 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  93                          size_t count)
  94 {
  95         struct i2c_client *client = to_i2c_client(dev);
  96         struct pcf8574_data *data = i2c_get_clientdata(client);
  97         unsigned long val = simple_strtoul(buf, NULL, 10);
  98
  99         if (val > 0xff)
 100                 return -EINVAL;
 101
 102         data->write = val;
 103         i2c_smbus_write_byte(client, data->write);
 104         return count;
 105 }
 106
 107 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 108
 109 static struct attribute *pcf8574_attributes[] = {
 110         &dev_attr_read.attr,
 111         &dev_attr_write.attr,
 112         NULL
 113 };
 114
 115 static const struct attribute_group pcf8574_attr_group = {
 116         .attrs = pcf8574_attributes,
 117 };
 118
 119 /*
 120  * Real code
 121  */
 122
 123 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 124 {
 125         return i2c_probe(adapter, &addr_data, pcf8574_detect);
 126 }
 127
 128 /* This function is called by i2c_probe */
 129 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 130 {
 131         struct i2c_client *new_client;
 132         struct pcf8574_data *data;
 133         int err = 0;
 134         const char *client_name = "";
 135
 136         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 137                 goto exit;
 138
 139         /* OK. For now, we presume we have a valid client. We now create the
 140            client structure, even though we cannot fill it completely yet. */
 141         if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 142                 err = -ENOMEM;
 143                 goto exit;
 144         }
 145
 146         new_client = &data->client;
 147         i2c_set_clientdata(new_client, data);
 148         new_client->addr = address;
 149         new_client->adapter = adapter;
 150         new_client->driver = &pcf8574_driver;
 151         new_client->flags = 0;
 152
 153         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 154            impossible to detect! Stupid chip. */
 155
 156         /* Determine the chip type */
 157         if (kind <= 0) {
 158                 if (address >= 0x38 && address <= 0x3f)
 159                         kind = pcf8574a;
 160                 else
 161                         kind = pcf8574;
 162         }
 163
 164         if (kind == pcf8574a)
 165                 client_name = "pcf8574a";
 166         else
 167                 client_name = "pcf8574";
 168
 169         /* Fill in the remaining client fields and put it into the global list */
 170         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 171
 172         /* Tell the I2C layer a new client has arrived */
 173         if ((err = i2c_attach_client(new_client)))
 174                 goto exit_free;
 175
 176         /* Initialize the PCF8574 chip */
 177         pcf8574_init_client(new_client);
 178
 179         /* Register sysfs hooks */
 180         err = sysfs_create_group(&new_client->dev.kobj, &pcf8574_attr_group);
 181         if (err)
 182                 goto exit_detach;
 183         return 0;
 184
 185       exit_detach:
 186         i2c_detach_client(new_client);
 187       exit_free:
 188         kfree(data);
 189       exit:
 190         return err;
 191 }
 192
 193 static int pcf8574_detach_client(struct i2c_client *client)
 194 {
 195         int err;
 196
 197         sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
 198
 199         if ((err = i2c_detach_client(client)))
 200                 return err;
 201
 202         kfree(i2c_get_clientdata(client));
 203         return 0;
 204 }
 205
 206 /* Called when we have found a new PCF8574. */
 207 static void pcf8574_init_client(struct i2c_client *client)
 208 {
 209         struct pcf8574_data *data = i2c_get_clientdata(client);
 210         data->write = -EAGAIN;
 211 }
 212
 213 static int __init pcf8574_init(void)
 214 {
 215         return i2c_add_driver(&pcf8574_driver);
 216 }
 217
 218 static void __exit pcf8574_exit(void)
 219 {
 220         i2c_del_driver(&pcf8574_driver);
 221 }
 222
 223
 224 MODULE_AUTHOR
 225     ("Frodo Looijaard <frodol@dds.nl>, "
 226      "Philip Edelbrock <phil@netroedge.com>, "
 227      "Dan Eaton <dan.eaton@rocketlogix.com> "
 228      "and Aurelien Jarno <aurelien@aurel32.net>");
 229 MODULE_DESCRIPTION("PCF8574 driver");
 230 MODULE_LICENSE("GPL");
 231
 232 module_init(pcf8574_init);
 233 module_exit(pcf8574_exit);