forked from Minki/linux
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>
This commit is contained in:
Bart Van Assche
Jean Delvare
parent
217bcec442
commit
5864ae03ca
72
Documentation/i2c/chips/pcf8575
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72
Documentation/i2c/chips/pcf8575
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@ -0,0 +1,72 @@
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About the PCF8575 chip and the pcf8575 kernel driver
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====================================================
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The PCF8575 chip is produced by the following manufacturers:
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* Philips NXP
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http://www.nxp.com/#/pip/cb=[type=product,path=50807/41735/41850,final=PCF8575_3]|pip=[pip=PCF8575_3][0]
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* Texas Instruments
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http://focus.ti.com/docs/prod/folders/print/pcf8575.html
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Some vendors sell small PCB's with the PCF8575 mounted on it. You can connect
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such a board to a Linux host via e.g. an USB to I2C interface. Examples of
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PCB boards with a PCF8575:
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* SFE Breakout Board for PCF8575 I2C Expander by RobotShop
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http://www.robotshop.ca/home/products/robot-parts/electronics/adapters-converters/sfe-pcf8575-i2c-expander-board.html
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* Breakout Board for PCF8575 I2C Expander by Spark Fun Electronics
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http://www.sparkfun.com/commerce/product_info.php?products_id=8130
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Description
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-----------
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The PCF8575 chip is a 16-bit I/O expander for the I2C bus. Up to eight of
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these chips can be connected to the same I2C bus. You can find this
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chip on some custom designed hardware, but you won't find it on PC
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motherboards.
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The PCF8575 chip consists of a 16-bit quasi-bidirectional port and an I2C-bus
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interface. Each of the sixteen I/O's can be independently used as an input or
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an output. To set up an I/O pin as an input, you have to write a 1 to the
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corresponding output.
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For more information please see the datasheet.
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Detection
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---------
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There is no method known to detect whether a chip on a given I2C address is
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a PCF8575 or whether it is any other I2C device. So there are two alternatives
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to let the driver find the installed PCF8575 devices:
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- Load this driver after any other I2C driver for I2C devices with addresses
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in the range 0x20 .. 0x27.
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- Pass the I2C bus and address of the installed PCF8575 devices explicitly to
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the driver at load time via the probe=... or force=... parameters.
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/sys interface
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--------------
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For each address on which a PCF8575 chip was found or forced the following
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files will be created under /sys:
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* /sys/bus/i2c/devices/<bus>-<address>/read
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* /sys/bus/i2c/devices/<bus>-<address>/write
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where bus is the I2C bus number (0, 1, ...) and address is the four-digit
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hexadecimal representation of the 7-bit I2C address of the PCF8575
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(0020 .. 0027).
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The read file is read-only. Reading it will trigger an I2C read and will hence
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report the current input state for the pins configured as inputs, and the
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current output value for the pins configured as outputs.
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The write file is read-write. Writing a value to it will configure all pins
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as output for which the corresponding bit is zero. Reading the write file will
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return the value last written, or -EAGAIN if no value has yet been written to
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the write file.
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On module initialization the configuration of the chip is not changed -- the
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chip is left in the state it was already configured in through either power-up
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or through previous I2C write actions.
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@ -57,7 +57,7 @@ config SENSORS_PCF8574
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default n
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help
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If you say yes here you get support for Philips PCF8574 and
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PCF8574A chips.
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PCF8574A chips. These chips are 8-bit I/O expanders for the I2C bus.
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This driver can also be built as a module. If so, the module
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will be called pcf8574.
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@ -65,6 +65,20 @@ config SENSORS_PCF8574
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These devices are hard to detect and rarely found on mainstream
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hardware. If unsure, say N.
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config PCF8575
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tristate "Philips PCF8575"
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default n
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help
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If you say yes here you get support for Philips PCF8575 chip.
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This chip is a 16-bit I/O expander for the I2C bus. Several other
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chip manufacturers sell equivalent chips, e.g. Texas Instruments.
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This driver can also be built as a module. If so, the module
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will be called pcf8575.
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This device is hard to detect and is rarely found on mainstream
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hardware. If unsure, say N.
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config SENSORS_PCA9539
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tristate "Philips PCA9539 16-bit I/O port"
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depends on EXPERIMENTAL
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@ -10,6 +10,7 @@ obj-$(CONFIG_SENSORS_MAX6875) += max6875.o
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obj-$(CONFIG_SENSORS_M41T00) += m41t00.o
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obj-$(CONFIG_SENSORS_PCA9539) += pca9539.o
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obj-$(CONFIG_SENSORS_PCF8574) += pcf8574.o
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obj-$(CONFIG_PCF8575) += pcf8575.o
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obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o
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obj-$(CONFIG_ISP1301_OMAP) += isp1301_omap.o
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obj-$(CONFIG_TPS65010) += tps65010.o
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214
drivers/i2c/chips/pcf8575.c
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214
drivers/i2c/chips/pcf8575.c
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@ -0,0 +1,214 @@
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/*
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pcf8575.c
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About the PCF8575 chip: the PCF8575 is a 16-bit I/O expander for the I2C bus
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produced by a.o. Philips Semiconductors.
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Copyright (C) 2006 Michael Hennerich, Analog Devices Inc.
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<hennerich@blackfin.uclinux.org>
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Based on pcf8574.c.
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Copyright (c) 2007 Bart Van Assche <bart.vanassche@gmail.com>.
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Ported this driver from ucLinux to the mainstream Linux kernel.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/i2c.h>
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#include <linux/slab.h> /* kzalloc() */
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#include <linux/sysfs.h> /* sysfs_create_group() */
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/* Addresses to scan */
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static unsigned short normal_i2c[] = {
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0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
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I2C_CLIENT_END
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};
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/* Insmod parameters */
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I2C_CLIENT_INSMOD;
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/* Each client has this additional data */
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struct pcf8575_data {
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struct i2c_client client;
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int write; /* last written value, or error code */
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};
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static int pcf8575_attach_adapter(struct i2c_adapter *adapter);
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static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind);
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static int pcf8575_detach_client(struct i2c_client *client);
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/* This is the driver that will be inserted */
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static struct i2c_driver pcf8575_driver = {
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.driver = {
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.owner = THIS_MODULE,
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.name = "pcf8575",
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},
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.attach_adapter = pcf8575_attach_adapter,
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.detach_client = pcf8575_detach_client,
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};
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/* following are the sysfs callback functions */
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static ssize_t show_read(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct i2c_client *client = to_i2c_client(dev);
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u16 val;
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u8 iopin_state[2];
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i2c_master_recv(client, iopin_state, 2);
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val = iopin_state[0];
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val |= iopin_state[1] << 8;
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return sprintf(buf, "%u\n", val);
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}
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static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
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static ssize_t show_write(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct pcf8575_data *data = dev_get_drvdata(dev);
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if (data->write < 0)
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return data->write;
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return sprintf(buf, "%d\n", data->write);
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}
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static ssize_t set_write(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct i2c_client *client = to_i2c_client(dev);
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struct pcf8575_data *data = i2c_get_clientdata(client);
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unsigned long val = simple_strtoul(buf, NULL, 10);
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u8 iopin_state[2];
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if (val > 0xffff)
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return -EINVAL;
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data->write = val;
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iopin_state[0] = val & 0xFF;
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iopin_state[1] = val >> 8;
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i2c_master_send(client, iopin_state, 2);
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return count;
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}
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static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
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static struct attribute *pcf8575_attributes[] = {
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&dev_attr_read.attr,
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&dev_attr_write.attr,
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NULL
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};
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static const struct attribute_group pcf8575_attr_group = {
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.attrs = pcf8575_attributes,
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};
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/*
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* Real code
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*/
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static int pcf8575_attach_adapter(struct i2c_adapter *adapter)
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{
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return i2c_probe(adapter, &addr_data, pcf8575_detect);
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}
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/* This function is called by i2c_probe */
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static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind)
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{
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struct i2c_client *client;
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struct pcf8575_data *data;
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int err = 0;
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if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
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goto exit;
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/* OK. For now, we presume we have a valid client. We now create the
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client structure, even though we cannot fill it completely yet. */
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data = kzalloc(sizeof(struct pcf8575_data), GFP_KERNEL);
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if (!data) {
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err = -ENOMEM;
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goto exit;
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}
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client = &data->client;
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i2c_set_clientdata(client, data);
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client->addr = address;
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client->adapter = adapter;
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client->driver = &pcf8575_driver;
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strlcpy(client->name, "pcf8575", I2C_NAME_SIZE);
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data->write = -EAGAIN;
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/* This is the place to detect whether the chip at the specified
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address really is a PCF8575 chip. However, there is no method known
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to detect whether an I2C chip is a PCF8575 or any other I2C chip. */
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/* Tell the I2C layer a new client has arrived */
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err = i2c_attach_client(client);
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if (err)
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goto exit_free;
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/* Register sysfs hooks */
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err = sysfs_create_group(&client->dev.kobj, &pcf8575_attr_group);
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if (err)
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goto exit_detach;
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return 0;
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exit_detach:
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i2c_detach_client(client);
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exit_free:
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kfree(data);
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exit:
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return err;
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}
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static int pcf8575_detach_client(struct i2c_client *client)
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{
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int err;
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sysfs_remove_group(&client->dev.kobj, &pcf8575_attr_group);
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err = i2c_detach_client(client);
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if (err)
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return err;
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kfree(i2c_get_clientdata(client));
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return 0;
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}
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static int __init pcf8575_init(void)
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{
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return i2c_add_driver(&pcf8575_driver);
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}
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static void __exit pcf8575_exit(void)
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{
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i2c_del_driver(&pcf8575_driver);
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}
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MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>, "
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"Bart Van Assche <bart.vanassche@gmail.com>");
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MODULE_DESCRIPTION("pcf8575 driver");
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MODULE_LICENSE("GPL");
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module_init(pcf8575_init);
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module_exit(pcf8575_exit);
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