Logo Search packages:      
Sourcecode: linux version File versions  Download package


    pcf8574.c - Part of lm_sensors, Linux kernel modules for hardware
    Copyright (c) 2000  Frodo Looijaard <frodol@dds.nl>, 
                        Philip Edelbrock <phil@netroedge.com>,
                        Dan Eaton <dan.eaton@rocketlogix.com>
    Ported to Linux 2.6 by Aurelien Jarno <aurel32@debian.org> with 
    the help of Jean Delvare <khali@linux-fr.org>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

/* A few notes about the PCF8574:

* The PCF8574 is an 8-bit I/O expander for the I2C bus produced by
  Philips Semiconductors.  It is designed to provide a byte I2C
  interface to up to 8 separate devices.
* The PCF8574 appears as a very simple SMBus device which can be
  read from or written to with SMBUS byte read/write accesses.



#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>

/* Addresses to scan */
static unsigned short normal_i2c[] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
                              0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
                              I2C_CLIENT_END };

/* Insmod parameters */
I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);

/* Each client has this additional data */
struct pcf8574_data {
      struct i2c_client client;

      int write;              /* Remember last written value */

static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
static int pcf8574_detach_client(struct i2c_client *client);
static void pcf8574_init_client(struct i2c_client *client);

/* This is the driver that will be inserted */
static struct i2c_driver pcf8574_driver = {
      .driver = {
            .name = "pcf8574",
      .id         = I2C_DRIVERID_PCF8574,
      .attach_adapter   = pcf8574_attach_adapter,
      .detach_client    = pcf8574_detach_client,

/* following are the sysfs callback functions */
static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
      struct i2c_client *client = to_i2c_client(dev);
      return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));

static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);

static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
      struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));

      if (data->write < 0)
            return data->write;

      return sprintf(buf, "%d\n", data->write);

static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
                   size_t count)
      struct i2c_client *client = to_i2c_client(dev);
      struct pcf8574_data *data = i2c_get_clientdata(client);
      unsigned long val = simple_strtoul(buf, NULL, 10);

      if (val > 0xff)
            return -EINVAL;

      data->write = val;
      i2c_smbus_write_byte(client, data->write);
      return count;

static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);

static struct attribute *pcf8574_attributes[] = {

static const struct attribute_group pcf8574_attr_group = {
      .attrs = pcf8574_attributes,

 * Real code

static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
      return i2c_probe(adapter, &addr_data, pcf8574_detect);

/* This function is called by i2c_probe */
static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
      struct i2c_client *new_client;
      struct pcf8574_data *data;
      int err = 0;
      const char *client_name = "";

      if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
            goto exit;

      /* OK. For now, we presume we have a valid client. We now create the
         client structure, even though we cannot fill it completely yet. */
      if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
            err = -ENOMEM;
            goto exit;

      new_client = &data->client;
      i2c_set_clientdata(new_client, data);
      new_client->addr = address;
      new_client->adapter = adapter;
      new_client->driver = &pcf8574_driver;
      new_client->flags = 0;

      /* Now, we would do the remaining detection. But the PCF8574 is plainly
         impossible to detect! Stupid chip. */

      /* Determine the chip type */
      if (kind <= 0) {
            if (address >= 0x38 && address <= 0x3f)
                  kind = pcf8574a;
                  kind = pcf8574;

      if (kind == pcf8574a)
            client_name = "pcf8574a";
            client_name = "pcf8574";

      /* Fill in the remaining client fields and put it into the global list */
      strlcpy(new_client->name, client_name, I2C_NAME_SIZE);

      /* Tell the I2C layer a new client has arrived */
      if ((err = i2c_attach_client(new_client)))
            goto exit_free;
      /* Initialize the PCF8574 chip */

      /* Register sysfs hooks */
      err = sysfs_create_group(&new_client->dev.kobj, &pcf8574_attr_group);
      if (err)
            goto exit_detach;
      return 0;

      return err;

static int pcf8574_detach_client(struct i2c_client *client)
      int err;

      sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);

      if ((err = i2c_detach_client(client)))
            return err;

      return 0;

/* Called when we have found a new PCF8574. */
static void pcf8574_init_client(struct i2c_client *client)
      struct pcf8574_data *data = i2c_get_clientdata(client);
      data->write = -EAGAIN;

static int __init pcf8574_init(void)
      return i2c_add_driver(&pcf8574_driver);

static void __exit pcf8574_exit(void)

    ("Frodo Looijaard <frodol@dds.nl>, "
     "Philip Edelbrock <phil@netroedge.com>, "
     "Dan Eaton <dan.eaton@rocketlogix.com> "
     "and Aurelien Jarno <aurelien@aurel32.net>");


Generated by  Doxygen 1.6.0   Back to index