i2c: Add support for the PCF8575 chip

Signed-off-by: Bart Van Assche <bart.vanassche@gmail.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/i2c/chips/pcf8575

+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.

drivers/i2c/chips/Kconfig

@@ -57,7 +57,7 @@ config SENSORS_PCF8574
 	default n
 	help
 	  If you say yes here you get support for Philips PCF8574 and 
-	  PCF8574A chips.
+	  PCF8574A chips. These chips are 8-bit I/O expanders for the I2C bus.
 
 	  This driver can also be built as a module.  If so, the module
 	  will be called pcf8574.
@@ -65,6 +65,20 @@ config SENSORS_PCF8574
 	  These devices are hard to detect and rarely found on mainstream
 	  hardware.  If unsure, say N.
 
+config PCF8575
+	tristate "Philips PCF8575"
+	default n
+	help
+	  If you say yes here you get support for Philips PCF8575 chip.
+	  This chip is a 16-bit I/O expander for the I2C bus.  Several other
+	  chip manufacturers sell equivalent chips, e.g. Texas Instruments.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called pcf8575.
+
+	  This device is hard to detect and is rarely found on mainstream
+	  hardware.  If unsure, say N.
+
 config SENSORS_PCA9539
 	tristate "Philips PCA9539 16-bit I/O port"
 	depends on EXPERIMENTAL

drivers/i2c/chips/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_SENSORS_MAX6875)	+= max6875.o
 obj-$(CONFIG_SENSORS_M41T00)	+= m41t00.o
 obj-$(CONFIG_SENSORS_PCA9539)	+= pca9539.o
 obj-$(CONFIG_SENSORS_PCF8574)	+= pcf8574.o
+obj-$(CONFIG_PCF8575)		+= pcf8575.o
 obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o
 obj-$(CONFIG_ISP1301_OMAP)	+= isp1301_omap.o
 obj-$(CONFIG_TPS65010)		+= tps65010.o

drivers/i2c/chips/pcf8575.c

+/*
+  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);