2 pcf8574.c - Part of lm_sensors, Linux kernel modules for hardware
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>
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.
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.
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.
25 /* A few notes about the PCF8574:
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.
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.
38 #include <linux/module.h>
39 #include <linux/init.h>
40 #include <linux/slab.h>
41 #include <linux/i2c.h>
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,
48 /* Insmod parameters */
49 I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);
52 #define PCF8574_INIT 255 /* All outputs on (input mode) */
54 /* Each client has this additional data */
56 struct i2c_client client;
58 u8 write; /* Remember last written value */
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);
66 /* This is the driver that will be inserted */
67 static struct i2c_driver pcf8574_driver = {
70 .id = I2C_DRIVERID_PCF8574,
71 .attach_adapter = pcf8574_attach_adapter,
72 .detach_client = pcf8574_detach_client,
75 /* following are the sysfs callback functions */
76 static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
78 struct i2c_client *client = to_i2c_client(dev);
79 return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
82 static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
84 static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
86 struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
87 return sprintf(buf, "%u\n", data->write);
90 static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
93 struct i2c_client *client = to_i2c_client(dev);
94 struct pcf8574_data *data = i2c_get_clientdata(client);
95 unsigned long val = simple_strtoul(buf, NULL, 10);
101 i2c_smbus_write_byte(client, data->write);
105 static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
111 static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
113 return i2c_probe(adapter, &addr_data, pcf8574_detect);
116 /* This function is called by i2c_probe */
117 static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
119 struct i2c_client *new_client;
120 struct pcf8574_data *data;
122 const char *client_name = "";
124 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
127 /* OK. For now, we presume we have a valid client. We now create the
128 client structure, even though we cannot fill it completely yet. */
129 if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
134 new_client = &data->client;
135 i2c_set_clientdata(new_client, data);
136 new_client->addr = address;
137 new_client->adapter = adapter;
138 new_client->driver = &pcf8574_driver;
139 new_client->flags = 0;
141 /* Now, we would do the remaining detection. But the PCF8574 is plainly
142 impossible to detect! Stupid chip. */
144 /* Determine the chip type */
146 if (address >= 0x38 && address <= 0x3f)
152 if (kind == pcf8574a)
153 client_name = "pcf8574a";
155 client_name = "pcf8574";
157 /* Fill in the remaining client fields and put it into the global list */
158 strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
160 /* Tell the I2C layer a new client has arrived */
161 if ((err = i2c_attach_client(new_client)))
164 /* Initialize the PCF8574 chip */
165 pcf8574_init_client(new_client);
167 /* Register sysfs hooks */
168 device_create_file(&new_client->dev, &dev_attr_read);
169 device_create_file(&new_client->dev, &dev_attr_write);
172 /* OK, this is not exactly good programming practice, usually. But it is
173 very code-efficient in this case. */
181 static int pcf8574_detach_client(struct i2c_client *client)
185 if ((err = i2c_detach_client(client)))
188 kfree(i2c_get_clientdata(client));
192 /* Called when we have found a new PCF8574. */
193 static void pcf8574_init_client(struct i2c_client *client)
195 struct pcf8574_data *data = i2c_get_clientdata(client);
196 data->write = PCF8574_INIT;
197 i2c_smbus_write_byte(client, data->write);
200 static int __init pcf8574_init(void)
202 return i2c_add_driver(&pcf8574_driver);
205 static void __exit pcf8574_exit(void)
207 i2c_del_driver(&pcf8574_driver);
212 ("Frodo Looijaard <frodol@dds.nl>, "
213 "Philip Edelbrock <phil@netroedge.com>, "
214 "Dan Eaton <dan.eaton@rocketlogix.com> "
215 "and Aurelien Jarno <aurelien@aurel32.net>");
216 MODULE_DESCRIPTION("PCF8574 driver");
217 MODULE_LICENSE("GPL");
219 module_init(pcf8574_init);
220 module_exit(pcf8574_exit);