--- /dev/null
+About the PCF8575 chip and the pcf8575 kernel driver
+====================================================
+
+The PCF8575 chip is produced by the following manufacturers:
+
+ * Philips NXP
+ http://www.nxp.com/#/pip/cb=[type=product,path=50807/41735/41850,final=PCF8575_3]|pip=[pip=PCF8575_3][0]
+
+ * Texas Instruments
+ http://focus.ti.com/docs/prod/folders/print/pcf8575.html
+
+
+Some vendors sell small PCB's with the PCF8575 mounted on it. You can connect
+such a board to a Linux host via e.g. an USB to I2C interface. Examples of
+PCB boards with a PCF8575:
+
+ * SFE Breakout Board for PCF8575 I2C Expander by RobotShop
+ http://www.robotshop.ca/home/products/robot-parts/electronics/adapters-converters/sfe-pcf8575-i2c-expander-board.html
+
+ * Breakout Board for PCF8575 I2C Expander by Spark Fun Electronics
+ http://www.sparkfun.com/commerce/product_info.php?products_id=8130
+
+
+Description
+-----------
+The PCF8575 chip is a 16-bit I/O expander for the I2C bus. Up to eight of
+these chips can be connected to the same I2C bus. You can find this
+chip on some custom designed hardware, but you won't find it on PC
+motherboards.
+
+The PCF8575 chip consists of a 16-bit quasi-bidirectional port and an I2C-bus
+interface. Each of the sixteen I/O's can be independently used as an input or
+an output. To set up an I/O pin as an input, you have to write a 1 to the
+corresponding output.
+
+For more information please see the datasheet.
+
+
+Detection
+---------
+
+There is no method known to detect whether a chip on a given I2C address is
+a PCF8575 or whether it is any other I2C device. So there are two alternatives
+to let the driver find the installed PCF8575 devices:
+- Load this driver after any other I2C driver for I2C devices with addresses
+ in the range 0x20 .. 0x27.
+- Pass the I2C bus and address of the installed PCF8575 devices explicitly to
+ the driver at load time via the probe=... or force=... parameters.
+
+/sys interface
+--------------
+
+For each address on which a PCF8575 chip was found or forced the following
+files will be created under /sys:
+* /sys/bus/i2c/devices/<bus>-<address>/read
+* /sys/bus/i2c/devices/<bus>-<address>/write
+where bus is the I2C bus number (0, 1, ...) and address is the four-digit
+hexadecimal representation of the 7-bit I2C address of the PCF8575
+(0020 .. 0027).
+
+The read file is read-only. Reading it will trigger an I2C read and will hence
+report the current input state for the pins configured as inputs, and the
+current output value for the pins configured as outputs.
+
+The write file is read-write. Writing a value to it will configure all pins
+as output for which the corresponding bit is zero. Reading the write file will
+return the value last written, or -EAGAIN if no value has yet been written to
+the write file.
+
+On module initialization the configuration of the chip is not changed -- the
+chip is left in the state it was already configured in through either power-up
+or through previous I2C write actions.
--- /dev/null
+/*
+ pcf8575.c
+
+ About the PCF8575 chip: the PCF8575 is a 16-bit I/O expander for the I2C bus
+ produced by a.o. Philips Semiconductors.
+
+ Copyright (C) 2006 Michael Hennerich, Analog Devices Inc.
+ <hennerich@blackfin.uclinux.org>
+ Based on pcf8574.c.
+
+ Copyright (c) 2007 Bart Van Assche <bart.vanassche@gmail.com>.
+ Ported this driver from ucLinux to the mainstream Linux kernel.
+
+ 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
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ 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.
+*/
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/slab.h> /* kzalloc() */
+#include <linux/sysfs.h> /* sysfs_create_group() */
+
+/* Addresses to scan */
+static unsigned short normal_i2c[] = {
+ 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+ I2C_CLIENT_END
+};
+
+/* Insmod parameters */
+I2C_CLIENT_INSMOD;
+
+
+/* Each client has this additional data */
+struct pcf8575_data {
+ struct i2c_client client;
+ int write; /* last written value, or error code */
+};
+
+static int pcf8575_attach_adapter(struct i2c_adapter *adapter);
+static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind);
+static int pcf8575_detach_client(struct i2c_client *client);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver pcf8575_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "pcf8575",
+ },
+ .attach_adapter = pcf8575_attach_adapter,
+ .detach_client = pcf8575_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);
+ u16 val;
+ u8 iopin_state[2];
+
+ i2c_master_recv(client, iopin_state, 2);
+
+ val = iopin_state[0];
+ val |= iopin_state[1] << 8;
+
+ return sprintf(buf, "%u\n", val);
+}
+
+static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
+
+static ssize_t show_write(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct pcf8575_data *data = dev_get_drvdata(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 pcf8575_data *data = i2c_get_clientdata(client);
+ unsigned long val = simple_strtoul(buf, NULL, 10);
+ u8 iopin_state[2];
+
+ if (val > 0xffff)
+ return -EINVAL;
+
+ data->write = val;
+
+ iopin_state[0] = val & 0xFF;
+ iopin_state[1] = val >> 8;
+
+ i2c_master_send(client, iopin_state, 2);
+
+ return count;
+}
+
+static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
+
+static struct attribute *pcf8575_attributes[] = {
+ &dev_attr_read.attr,
+ &dev_attr_write.attr,
+ NULL
+};
+
+static const struct attribute_group pcf8575_attr_group = {
+ .attrs = pcf8575_attributes,
+};
+
+/*
+ * Real code
+ */
+
+static int pcf8575_attach_adapter(struct i2c_adapter *adapter)
+{
+ return i2c_probe(adapter, &addr_data, pcf8575_detect);
+}
+
+/* This function is called by i2c_probe */
+static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind)
+{
+ struct i2c_client *client;
+ struct pcf8575_data *data;
+ int err = 0;
+
+ if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
+ 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. */
+ data = kzalloc(sizeof(struct pcf8575_data), GFP_KERNEL);
+ if (!data) {
+ err = -ENOMEM;
+ goto exit;
+ }
+
+ client = &data->client;
+ i2c_set_clientdata(client, data);
+ client->addr = address;
+ client->adapter = adapter;
+ client->driver = &pcf8575_driver;
+ strlcpy(client->name, "pcf8575", I2C_NAME_SIZE);
+ data->write = -EAGAIN;
+
+ /* This is the place to detect whether the chip at the specified
+ address really is a PCF8575 chip. However, there is no method known
+ to detect whether an I2C chip is a PCF8575 or any other I2C chip. */
+
+ /* Tell the I2C layer a new client has arrived */
+ err = i2c_attach_client(client);
+ if (err)
+ goto exit_free;
+
+ /* Register sysfs hooks */
+ err = sysfs_create_group(&client->dev.kobj, &pcf8575_attr_group);
+ if (err)
+ goto exit_detach;
+
+ return 0;
+
+exit_detach:
+ i2c_detach_client(client);
+exit_free:
+ kfree(data);
+exit:
+ return err;
+}
+
+static int pcf8575_detach_client(struct i2c_client *client)
+{
+ int err;
+
+ sysfs_remove_group(&client->dev.kobj, &pcf8575_attr_group);
+
+ err = i2c_detach_client(client);
+ if (err)
+ return err;
+
+ kfree(i2c_get_clientdata(client));
+ return 0;
+}
+
+static int __init pcf8575_init(void)
+{
+ return i2c_add_driver(&pcf8575_driver);
+}
+
+static void __exit pcf8575_exit(void)
+{
+ i2c_del_driver(&pcf8575_driver);
+}
+
+MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>, "
+ "Bart Van Assche <bart.vanassche@gmail.com>");
+MODULE_DESCRIPTION("pcf8575 driver");
+MODULE_LICENSE("GPL");
+
+module_init(pcf8575_init);
+module_exit(pcf8575_exit);
projects / linux-2.6 / commitdiff