tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 pcf8574.c - Part of lm_sensors, Linux kernel modules for hardware
3 monitoring
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>
9
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.
14
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.
19
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.
23*/
24
25/* A few notes about the PCF8574:
26
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.
30
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.
33
34 --Dan
35
36*/
37
38#include <linux/module.h>
39#include <linux/init.h>
40#include <linux/slab.h>
41#include <linux/i2c.h>
42
43/* Addresses to scan */
44static unsigned short normal_i2c[] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
45 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
46 I2C_CLIENT_END };
47
48/* Insmod parameters */
49I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a);
50
51/* Each client has this additional data */
52struct pcf8574_data {
53 struct i2c_client client;
54
55 int write; /* Remember last written value */
56};
57
58static int pcf8574_attach_adapter(struct i2c_adapter *adapter);
59static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind);
60static int pcf8574_detach_client(struct i2c_client *client);
61static void pcf8574_init_client(struct i2c_client *client);
62
63/* This is the driver that will be inserted */
64static struct i2c_driver pcf8574_driver = {
65 .driver = {
66 .name = "pcf8574",
67 },
68 .id = I2C_DRIVERID_PCF8574,
69 .attach_adapter = pcf8574_attach_adapter,
70 .detach_client = pcf8574_detach_client,
71};
72
73/* following are the sysfs callback functions */
74static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
75{
76 struct i2c_client *client = to_i2c_client(dev);
77 return sprintf(buf, "%u\n", i2c_smbus_read_byte(client));
78}
79
80static DEVICE_ATTR(read, S_IRUGO, show_read, NULL);
81
82static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf)
83{
84 struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev));
85
86 if (data->write < 0)
87 return data->write;
88
89 return sprintf(buf, "%d\n", data->write);
90}
91
92static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf,
93 size_t count)
94{
95 struct i2c_client *client = to_i2c_client(dev);
96 struct pcf8574_data *data = i2c_get_clientdata(client);
97 unsigned long val = simple_strtoul(buf, NULL, 10);
98
99 if (val > 0xff)
100 return -EINVAL;
101
102 data->write = val;
103 i2c_smbus_write_byte(client, data->write);
104 return count;
105}
106
107static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write);
108
109static struct attribute *pcf8574_attributes[] = {
110 &dev_attr_read.attr,
111 &dev_attr_write.attr,
112 NULL
113};
114
115static const struct attribute_group pcf8574_attr_group = {
116 .attrs = pcf8574_attributes,
117};
118
119/*
120 * Real code
121 */
122
123static int pcf8574_attach_adapter(struct i2c_adapter *adapter)
124{
125 return i2c_probe(adapter, &addr_data, pcf8574_detect);
126}
127
128/* This function is called by i2c_probe */
129static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind)
130{
131 struct i2c_client *new_client;
132 struct pcf8574_data *data;
133 int err = 0;
134 const char *client_name = "";
135
136 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
137 goto exit;
138
139 /* OK. For now, we presume we have a valid client. We now create the
140 client structure, even though we cannot fill it completely yet. */
141 if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) {
142 err = -ENOMEM;
143 goto exit;
144 }
145
146 new_client = &data->client;
147 i2c_set_clientdata(new_client, data);
148 new_client->addr = address;
149 new_client->adapter = adapter;
150 new_client->driver = &pcf8574_driver;
151 new_client->flags = 0;
152
153 /* Now, we would do the remaining detection. But the PCF8574 is plainly
154 impossible to detect! Stupid chip. */
155
156 /* Determine the chip type */
157 if (kind <= 0) {
158 if (address >= 0x38 && address <= 0x3f)
159 kind = pcf8574a;
160 else
161 kind = pcf8574;
162 }
163
164 if (kind == pcf8574a)
165 client_name = "pcf8574a";
166 else
167 client_name = "pcf8574";
168
169 /* Fill in the remaining client fields and put it into the global list */
170 strlcpy(new_client->name, client_name, I2C_NAME_SIZE);
171
172 /* Tell the I2C layer a new client has arrived */
173 if ((err = i2c_attach_client(new_client)))
174 goto exit_free;
175
176 /* Initialize the PCF8574 chip */
177 pcf8574_init_client(new_client);
178
179 /* Register sysfs hooks */
180 err = sysfs_create_group(&new_client->dev.kobj, &pcf8574_attr_group);
181 if (err)
182 goto exit_detach;
183 return 0;
184
185 exit_detach:
186 i2c_detach_client(new_client);
187 exit_free:
188 kfree(data);
189 exit:
190 return err;
191}
192
193static int pcf8574_detach_client(struct i2c_client *client)
194{
195 int err;
196
197 sysfs_remove_group(&client->dev.kobj, &pcf8574_attr_group);
198
199 if ((err = i2c_detach_client(client)))
200 return err;
201
202 kfree(i2c_get_clientdata(client));
203 return 0;
204}
205
206/* Called when we have found a new PCF8574. */
207static void pcf8574_init_client(struct i2c_client *client)
208{
209 struct pcf8574_data *data = i2c_get_clientdata(client);
210 data->write = -EAGAIN;
211}
212
213static int __init pcf8574_init(void)
214{
215 return i2c_add_driver(&pcf8574_driver);
216}
217
218static void __exit pcf8574_exit(void)
219{
220 i2c_del_driver(&pcf8574_driver);
221}
222
223
224MODULE_AUTHOR
225 ("Frodo Looijaard <frodol@dds.nl>, "
226 "Philip Edelbrock <phil@netroedge.com>, "
227 "Dan Eaton <dan.eaton@rocketlogix.com> "
228 "and Aurelien Jarno <aurelien@aurel32.net>");
229MODULE_DESCRIPTION("PCF8574 driver");
230MODULE_LICENSE("GPL");
231
232module_init(pcf8574_init);
233module_exit(pcf8574_exit);