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[] = { I2C_CLIENT_END };
  46 static unsigned short normal_i2c_range[] = { 0x20, 0x27, 0x38, 0x3f, I2C_CLIENT_END };
  47 static unsigned int normal_isa[] = { I2C_CLIENT_ISA_END };
  48 static unsigned int normal_isa_range[] = { 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         struct semaphore update_lock;
  60
  61         u8 read, write;                 /* Register values */
  62 };
  63
  64 static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
  65 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
  66 static int pcf8574_detach_client(struct i2c_client *client);
  67 static void pcf8574_init_client(struct i2c_client *client);
  68 static struct pcf8574_data *pcf8574_update_client(struct device *dev);
  69
  70 /* This is the driver that will be inserted */
  71 static struct i2c_driver pcf8574_driver = {
  72         .owner          = THIS_MODULE,
  73         .name           = "pcf8574",
  74         .id             = I2C_DRIVERID_PCF8574,
  75         .flags          = I2C_DF_NOTIFY,
  76         .attach_adapter = pcf8574_attach_adapter,
  77         .detach_client  = pcf8574_detach_client,
  78 };
  79
  80 static int pcf8574_id = 0;
  81
  82 /* following are the sysfs callback functions */
  83 static ssize_t show_read(struct device *dev, char *buf)
  84 {
  85         struct pcf8574_data *data = pcf8574_update_client(dev);
  86         return sprintf(buf, "%u\n", data->read);
  87 }
  88
  89 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  90
  91 static ssize_t show_write(struct device *dev, char *buf)
  92 {
  93         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  94         return sprintf(buf, "%u\n", data->write);
  95 }
  96
  97 static ssize_t set_write(struct device *dev, const char *buf,
  98                          size_t count)
  99 {
 100         struct i2c_client *client = to_i2c_client(dev);
 101         struct pcf8574_data *data = i2c_get_clientdata(client);
 102         data->write = simple_strtoul(buf, NULL, 10);
 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 /*
 110  * Real code
 111  */
 112
 113 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 114 {
 115         return i2c_detect(adapter, &addr_data, pcf8574_detect);
 116 }
 117
 118 /* This function is called by i2c_detect */
 119 int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 120 {
 121         struct i2c_client *new_client;
 122         struct pcf8574_data *data;
 123         int err = 0;
 124         const char *client_name = "";
 125
 126         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 127                 goto exit;
 128
 129         /* OK. For now, we presume we have a valid client. We now create the
 130            client structure, even though we cannot fill it completely yet. */
 131         if (!(data = kmalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 132                 err = -ENOMEM;
 133                 goto exit;
 134         }
 135         memset(data, 0, sizeof(struct pcf8574_data));
 136
 137         new_client = &data->client;
 138         i2c_set_clientdata(new_client, data);
 139         new_client->addr = address;
 140         new_client->adapter = adapter;
 141         new_client->driver = &pcf8574_driver;
 142         new_client->flags = 0;
 143
 144         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 145            impossible to detect! Stupid chip. */
 146
 147         /* Determine the chip type */
 148         if (kind <= 0) {
 149                 if (address >= 0x38 && address <= 0x3f)
 150                         kind = pcf8574a;
 151                 else
 152                         kind = pcf8574;
 153         }
 154
 155         if (kind == pcf8574a)
 156                 client_name = "pcf8574a";
 157         else
 158                 client_name = "pcf8574";
 159
 160         /* Fill in the remaining client fields and put it into the global list */
 161         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 162
 163         new_client->id = pcf8574_id++;
 164         init_MUTEX(&data->update_lock);
 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 struct pcf8574_data *pcf8574_update_client(struct device *dev)
 210 {
 211         struct i2c_client *client = to_i2c_client(dev);
 212         struct pcf8574_data *data = i2c_get_clientdata(client);
 213
 214         down(&data->update_lock);
 215         dev_dbg(&client->dev, "Starting pcf8574 update\n");
 216         data->read = i2c_smbus_read_byte(client);
 217         up(&data->update_lock);
 218
 219         return data;
 220 }
 221
 222 static int __init pcf8574_init(void)
 223 {
 224         return i2c_add_driver(&pcf8574_driver);
 225 }
 226
 227 static void __exit pcf8574_exit(void)
 228 {
 229         i2c_del_driver(&pcf8574_driver);
 230 }
 231
 232
 233 MODULE_AUTHOR
 234     ("Frodo Looijaard <frodol@dds.nl>, "
 235      "Philip Edelbrock <phil@netroedge.com>, "
 236      "Dan Eaton <dan.eaton@rocketlogix.com> "
 237      "and Aurelien Jarno <aurelien@aurel32.net>");
 238 MODULE_DESCRIPTION("PCF8574 driver");
 239 MODULE_LICENSE("GPL");
 240
 241 module_init(pcf8574_init);
 242 module_exit(pcf8574_exit);