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
= {
71 .id
= I2C_DRIVERID_PCF8574
,
72 .attach_adapter
= pcf8574_attach_adapter
,
73 .detach_client
= pcf8574_detach_client
,
76 /* following are the sysfs callback functions */
77 static ssize_t
show_read(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
79 struct i2c_client
*client
= to_i2c_client(dev
);
80 return sprintf(buf
, "%u\n", i2c_smbus_read_byte(client
));
83 static DEVICE_ATTR(read
, S_IRUGO
, show_read
, NULL
);
85 static ssize_t
show_write(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
87 struct pcf8574_data
*data
= i2c_get_clientdata(to_i2c_client(dev
));
88 return sprintf(buf
, "%u\n", data
->write
);
91 static ssize_t
set_write(struct device
*dev
, struct device_attribute
*attr
, const char *buf
,
94 struct i2c_client
*client
= to_i2c_client(dev
);
95 struct pcf8574_data
*data
= i2c_get_clientdata(client
);
96 unsigned long val
= simple_strtoul(buf
, NULL
, 10);
102 i2c_smbus_write_byte(client
, data
->write
);
106 static DEVICE_ATTR(write
, S_IWUSR
| S_IRUGO
, show_write
, set_write
);
112 static int pcf8574_attach_adapter(struct i2c_adapter
*adapter
)
114 return i2c_probe(adapter
, &addr_data
, pcf8574_detect
);
117 /* This function is called by i2c_probe */
118 static int pcf8574_detect(struct i2c_adapter
*adapter
, int address
, int kind
)
120 struct i2c_client
*new_client
;
121 struct pcf8574_data
*data
;
123 const char *client_name
= "";
125 if (!i2c_check_functionality(adapter
, I2C_FUNC_SMBUS_BYTE
))
128 /* OK. For now, we presume we have a valid client. We now create the
129 client structure, even though we cannot fill it completely yet. */
130 if (!(data
= kzalloc(sizeof(struct pcf8574_data
), GFP_KERNEL
))) {
135 new_client
= &data
->client
;
136 i2c_set_clientdata(new_client
, data
);
137 new_client
->addr
= address
;
138 new_client
->adapter
= adapter
;
139 new_client
->driver
= &pcf8574_driver
;
140 new_client
->flags
= 0;
142 /* Now, we would do the remaining detection. But the PCF8574 is plainly
143 impossible to detect! Stupid chip. */
145 /* Determine the chip type */
147 if (address
>= 0x38 && address
<= 0x3f)
153 if (kind
== pcf8574a
)
154 client_name
= "pcf8574a";
156 client_name
= "pcf8574";
158 /* Fill in the remaining client fields and put it into the global list */
159 strlcpy(new_client
->name
, client_name
, I2C_NAME_SIZE
);
161 /* Tell the I2C layer a new client has arrived */
162 if ((err
= i2c_attach_client(new_client
)))
165 /* Initialize the PCF8574 chip */
166 pcf8574_init_client(new_client
);
168 /* Register sysfs hooks */
169 device_create_file(&new_client
->dev
, &dev_attr_read
);
170 device_create_file(&new_client
->dev
, &dev_attr_write
);
173 /* OK, this is not exactly good programming practice, usually. But it is
174 very code-efficient in this case. */
182 static int pcf8574_detach_client(struct i2c_client
*client
)
186 if ((err
= i2c_detach_client(client
)))
189 kfree(i2c_get_clientdata(client
));
193 /* Called when we have found a new PCF8574. */
194 static void pcf8574_init_client(struct i2c_client
*client
)
196 struct pcf8574_data
*data
= i2c_get_clientdata(client
);
197 data
->write
= PCF8574_INIT
;
198 i2c_smbus_write_byte(client
, data
->write
);
201 static int __init
pcf8574_init(void)
203 return i2c_add_driver(&pcf8574_driver
);
206 static void __exit
pcf8574_exit(void)
208 i2c_del_driver(&pcf8574_driver
);
213 ("Frodo Looijaard <frodol@dds.nl>, "
214 "Philip Edelbrock <phil@netroedge.com>, "
215 "Dan Eaton <dan.eaton@rocketlogix.com> "
216 "and Aurelien Jarno <aurelien@aurel32.net>");
217 MODULE_DESCRIPTION("PCF8574 driver");
218 MODULE_LICENSE("GPL");
220 module_init(pcf8574_init
);
221 module_exit(pcf8574_exit
);