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 #include <linux/i2c-sensor.h>
  43
  44 /* Addresses to scan */
  45 static unsigned short normal_i2c[] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
  46                                         0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
  47                                         I2C_CLIENT_END };
  48 static unsigned int normal_isa[] = { I2C_CLIENT_ISA_END };
  49
  50 /* Insmod parameters */
  51 SENSORS_INSMOD_2(pcf8574, pcf8574a);
  52
  53 /* Initial values */
  54 #define PCF8574_INIT 255        /* All outputs on (input mode) */
  55
  56 /* Each client has this additional data */
  57 struct pcf8574_data {
  58         struct i2c_client client;
  59
  60         u8 read, write;                 /* Register values */
  61 };
  62
  63 static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
  64 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
  65 static int pcf8574_detach_client(struct i2c_client *client);
  66 static void pcf8574_init_client(struct i2c_client *client);
  67
  68 /* This is the driver that will be inserted */
  69 static struct i2c_driver pcf8574_driver = {
  70         .owner          = THIS_MODULE,
  71         .name           = "pcf8574",
  72         .id             = I2C_DRIVERID_PCF8574,
  73         .flags          = I2C_DF_NOTIFY,
  74         .attach_adapter = pcf8574_attach_adapter,
  75         .detach_client  = pcf8574_detach_client,
  76 };
  77
  78 /* following are the sysfs callback functions */
  79 static ssize_t show_read(struct device *dev, char *buf)
  80 {
  81         struct i2c_client *client = to_i2c_client(dev);
  82         struct pcf8574_data *data = i2c_get_clientdata(client);
  83         data->read = i2c_smbus_read_byte(client);
  84         return sprintf(buf, "%u\n", data->read);
  85 }
  86
  87 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  88
  89 static ssize_t show_write(struct device *dev, char *buf)
  90 {
  91         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  92         return sprintf(buf, "%u\n", data->write);
  93 }
  94
  95 static ssize_t set_write(struct device *dev, const char *buf,
  96                          size_t count)
  97 {
  98         struct i2c_client *client = to_i2c_client(dev);
  99         struct pcf8574_data *data = i2c_get_clientdata(client);
 100         unsigned long val = simple_strtoul(buf, NULL, 10);
 101
 102         if (val > 0xff)
 103                 return -EINVAL;
 104
 105         data->write = val;
 106         i2c_smbus_write_byte(client, data->write);
 107         return count;
 108 }
 109
 110 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 111
 112 /*
 113  * Real code
 114  */
 115
 116 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 117 {
 118         return i2c_detect(adapter, &addr_data, pcf8574_detect);
 119 }
 120
 121 /* This function is called by i2c_detect */
 122 int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 123 {
 124         struct i2c_client *new_client;
 125         struct pcf8574_data *data;
 126         int err = 0;
 127         const char *client_name = "";
 128
 129         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 130                 goto exit;
 131
 132         /* OK. For now, we presume we have a valid client. We now create the
 133            client structure, even though we cannot fill it completely yet. */
 134         if (!(data = kmalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 135                 err = -ENOMEM;
 136                 goto exit;
 137         }
 138         memset(data, 0, sizeof(struct pcf8574_data));
 139
 140         new_client = &data->client;
 141         i2c_set_clientdata(new_client, data);
 142         new_client->addr = address;
 143         new_client->adapter = adapter;
 144         new_client->driver = &pcf8574_driver;
 145         new_client->flags = 0;
 146
 147         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 148            impossible to detect! Stupid chip. */
 149
 150         /* Determine the chip type */
 151         if (kind <= 0) {
 152                 if (address >= 0x38 && address <= 0x3f)
 153                         kind = pcf8574a;
 154                 else
 155                         kind = pcf8574;
 156         }
 157
 158         if (kind == pcf8574a)
 159                 client_name = "pcf8574a";
 160         else
 161                 client_name = "pcf8574";
 162
 163         /* Fill in the remaining client fields and put it into the global list */
 164         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 165
 166         /* Tell the I2C layer a new client has arrived */
 167         if ((err = i2c_attach_client(new_client)))
 168                 goto exit_free;
 169
 170         /* Initialize the PCF8574 chip */
 171         pcf8574_init_client(new_client);
 172
 173         /* Register sysfs hooks */
 174         device_create_file(&new_client->dev, &dev_attr_read);
 175         device_create_file(&new_client->dev, &dev_attr_write);
 176         return 0;
 177
 178 /* OK, this is not exactly good programming practice, usually. But it is
 179    very code-efficient in this case. */
 180
 181       exit_free:
 182         kfree(data);
 183       exit:
 184         return err;
 185 }
 186
 187 static int pcf8574_detach_client(struct i2c_client *client)
 188 {
 189         int err;
 190
 191         if ((err = i2c_detach_client(client))) {
 192                 dev_err(&client->dev,
 193                         "Client deregistration failed, client not detached.\n");
 194                 return err;
 195         }
 196
 197         kfree(i2c_get_clientdata(client));
 198         return 0;
 199 }
 200
 201 /* Called when we have found a new PCF8574. */
 202 static void pcf8574_init_client(struct i2c_client *client)
 203 {
 204         struct pcf8574_data *data = i2c_get_clientdata(client);
 205         data->write = PCF8574_INIT;
 206         i2c_smbus_write_byte(client, data->write);
 207 }
 208
 209 static int __init pcf8574_init(void)
 210 {
 211         return i2c_add_driver(&pcf8574_driver);
 212 }
 213
 214 static void __exit pcf8574_exit(void)
 215 {
 216         i2c_del_driver(&pcf8574_driver);
 217 }
 218
 219
 220 MODULE_AUTHOR
 221     ("Frodo Looijaard <frodol@dds.nl>, "
 222      "Philip Edelbrock <phil@netroedge.com>, "
 223      "Dan Eaton <dan.eaton@rocketlogix.com> "
 224      "and Aurelien Jarno <aurelien@aurel32.net>");
 225 MODULE_DESCRIPTION("PCF8574 driver");
 226 MODULE_LICENSE("GPL");
 227
 228 module_init(pcf8574_init);
 229 module_exit(pcf8574_exit);