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 /* Initial values */
  52 #define PCF8574_INIT 255        /* All outputs on (input mode) */
  53
  54 /* Each client has this additional data */
  55 struct pcf8574_data {
  56         struct i2c_client client;
  57
  58         u8 write;                       /* Remember last written value */
  59 };
  60
  61 static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
  62 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
  63 static int pcf8574_detach_client(struct i2c_client *client);
  64 static void pcf8574_init_client(struct i2c_client *client);
  65
  66 /* This is the driver that will be inserted */
  67 static struct i2c_driver pcf8574_driver = {
  68         .driver = {
  69                 .name   = "pcf8574",
  70         },
  71         .id             = I2C_DRIVERID_PCF8574,
  72         .attach_adapter = pcf8574_attach_adapter,
  73         .detach_client  = pcf8574_detach_client,
  74 };
  75
  76 /* following are the sysfs callback functions */
  77 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
  78 {
  79         struct i2c_client *client = to_i2c_client(dev);
  80         return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
  81 }
  82
  83 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
  84
  85 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
  86 {
  87         struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
  88         return sprintf(buf, "%u\n", data->write);
  89 }
  90
  91 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
  92                          size_t count)
  93 {
  94         struct i2c_client *client = to_i2c_client(dev);
  95         struct pcf8574_data *data = i2c_get_clientdata(client);
  96         unsigned long val = simple_strtoul(buf, NULL, 10);
  97
  98         if (val > 0xff)
  99                 return -EINVAL;
 100
 101         data->write = val;
 102         i2c_smbus_write_byte(client, data->write);
 103         return count;
 104 }
 105
 106 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
 107
 108 /*
 109  * Real code
 110  */
 111
 112 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
 113 {
 114         return i2c_probe(adapter, &addr_data, pcf8574_detect);
 115 }
 116
 117 /* This function is called by i2c_probe */
 118 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
 119 {
 120         struct i2c_client *new_client;
 121         struct pcf8574_data *data;
 122         int err = 0;
 123         const char *client_name = "";
 124
 125         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
 126                 goto exit;
 127
 128         /* OK. For now, we presume we have a valid client. We now create the
 129            client structure, even though we cannot fill it completely yet. */
 130         if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
 131                 err = -ENOMEM;
 132                 goto exit;
 133         }
 134
 135         new_client = &data->client;
 136         i2c_set_clientdata(new_client, data);
 137         new_client->addr = address;
 138         new_client->adapter = adapter;
 139         new_client->driver = &pcf8574_driver;
 140         new_client->flags = 0;
 141
 142         /* Now, we would do the remaining detection. But the PCF8574 is plainly
 143            impossible to detect! Stupid chip. */
 144
 145         /* Determine the chip type */
 146         if (kind <= 0) {
 147                 if (address >= 0x38 && address <= 0x3f)
 148                         kind = pcf8574a;
 149                 else
 150                         kind = pcf8574;
 151         }
 152
 153         if (kind == pcf8574a)
 154                 client_name = "pcf8574a";
 155         else
 156                 client_name = "pcf8574";
 157
 158         /* Fill in the remaining client fields and put it into the global list */
 159         strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
 160
 161         /* Tell the I2C layer a new client has arrived */
 162         if ((err = i2c_attach_client(new_client)))
 163                 goto exit_free;
 164
 165         /* Initialize the PCF8574 chip */
 166         pcf8574_init_client(new_client);
 167
 168         /* Register sysfs hooks */
 169         device_create_file(&new_client->dev, &dev_attr_read);
 170         device_create_file(&new_client->dev, &dev_attr_write);
 171         return 0;
 172
 173 /* OK, this is not exactly good programming practice, usually. But it is
 174    very code-efficient in this case. */
 175
 176       exit_free:
 177         kfree(data);
 178       exit:
 179         return err;
 180 }
 181
 182 static int pcf8574_detach_client(struct i2c_client *client)
 183 {
 184         int err;
 185
 186         if ((err = i2c_detach_client(client)))
 187                 return err;
 188
 189         kfree(i2c_get_clientdata(client));
 190         return 0;
 191 }
 192
 193 /* Called when we have found a new PCF8574. */
 194 static void pcf8574_init_client(struct i2c_client *client)
 195 {
 196         struct pcf8574_data *data = i2c_get_clientdata(client);
 197         data->write = PCF8574_INIT;
 198         i2c_smbus_write_byte(client, data->write);
 199 }
 200
 201 static int __init pcf8574_init(void)
 202 {
 203         return i2c_add_driver(&pcf8574_driver);
 204 }
 205
 206 static void __exit pcf8574_exit(void)
 207 {
 208         i2c_del_driver(&pcf8574_driver);
 209 }
 210
 211
 212 MODULE_AUTHOR
 213     ("Frodo Looijaard <frodol@dds.nl>, "
 214      "Philip Edelbrock <phil@netroedge.com>, "
 215      "Dan Eaton <dan.eaton@rocketlogix.com> "
 216      "and Aurelien Jarno <aurelien@aurel32.net>");
 217 MODULE_DESCRIPTION("PCF8574 driver");
 218 MODULE_LICENSE("GPL");
 219
 220 module_init(pcf8574_init);
 221 module_exit(pcf8574_exit);