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
);
51 /* Each client has this additional data */
53 struct i2c_client client
;
55 int write
; /* Remember last written value */
58 static int pcf8574_attach_adapter(struct i2c_adapter
*adapter
);
59 static int pcf8574_detect(struct i2c_adapter
*adapter
, int address
, int kind
);
60 static int pcf8574_detach_client(struct i2c_client
*client
);
61 static void pcf8574_init_client(struct i2c_client
*client
);
63 /* This is the driver that will be inserted */
64 static struct i2c_driver pcf8574_driver
= {
68 .id
= I2C_DRIVERID_PCF8574
,
69 .attach_adapter
= pcf8574_attach_adapter
,
70 .detach_client
= pcf8574_detach_client
,
73 /* following are the sysfs callback functions */
74 static ssize_t
show_read(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
76 struct i2c_client
*client
= to_i2c_client(dev
);
77 return sprintf(buf
, "%u\n", i2c_smbus_read_byte(client
));
80 static DEVICE_ATTR(read
, S_IRUGO
, show_read
, NULL
);
82 static ssize_t
show_write(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
84 struct pcf8574_data
*data
= i2c_get_clientdata(to_i2c_client(dev
));
89 return sprintf(buf
, "%d\n", data
->write
);
92 static ssize_t
set_write(struct device
*dev
, struct device_attribute
*attr
, const char *buf
,
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);
103 i2c_smbus_write_byte(client
, data
->write
);
107 static DEVICE_ATTR(write
, S_IWUSR
| S_IRUGO
, show_write
, set_write
);
109 static struct attribute
*pcf8574_attributes
[] = {
111 &dev_attr_write
.attr
,
115 static const struct attribute_group pcf8574_attr_group
= {
116 .attrs
= pcf8574_attributes
,
123 static int pcf8574_attach_adapter(struct i2c_adapter
*adapter
)
125 return i2c_probe(adapter
, &addr_data
, pcf8574_detect
);
128 /* This function is called by i2c_probe */
129 static int pcf8574_detect(struct i2c_adapter
*adapter
, int address
, int kind
)
131 struct i2c_client
*new_client
;
132 struct pcf8574_data
*data
;
134 const char *client_name
= "";
136 if (!i2c_check_functionality(adapter
, I2C_FUNC_SMBUS_BYTE
))
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
))) {
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;
153 /* Now, we would do the remaining detection. But the PCF8574 is plainly
154 impossible to detect! Stupid chip. */
156 /* Determine the chip type */
158 if (address
>= 0x38 && address
<= 0x3f)
164 if (kind
== pcf8574a
)
165 client_name
= "pcf8574a";
167 client_name
= "pcf8574";
169 /* Fill in the remaining client fields and put it into the global list */
170 strlcpy(new_client
->name
, client_name
, I2C_NAME_SIZE
);
172 /* Tell the I2C layer a new client has arrived */
173 if ((err
= i2c_attach_client(new_client
)))
176 /* Initialize the PCF8574 chip */
177 pcf8574_init_client(new_client
);
179 /* Register sysfs hooks */
180 err
= sysfs_create_group(&new_client
->dev
.kobj
, &pcf8574_attr_group
);
186 i2c_detach_client(new_client
);
193 static int pcf8574_detach_client(struct i2c_client
*client
)
197 sysfs_remove_group(&client
->dev
.kobj
, &pcf8574_attr_group
);
199 if ((err
= i2c_detach_client(client
)))
202 kfree(i2c_get_clientdata(client
));
206 /* Called when we have found a new PCF8574. */
207 static void pcf8574_init_client(struct i2c_client
*client
)
209 struct pcf8574_data
*data
= i2c_get_clientdata(client
);
210 data
->write
= -EAGAIN
;
213 static int __init
pcf8574_init(void)
215 return i2c_add_driver(&pcf8574_driver
);
218 static void __exit
pcf8574_exit(void)
220 i2c_del_driver(&pcf8574_driver
);
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>");
229 MODULE_DESCRIPTION("PCF8574 driver");
230 MODULE_LICENSE("GPL");
232 module_init(pcf8574_init
);
233 module_exit(pcf8574_exit
);