/* pcf8574.c - Part of lm_sensors, Linux kernel modules for hardware monitoring Copyright (c) 2000 Frodo Looijaard , Philip Edelbrock , Dan Eaton Ported to Linux 2.6 by Aurelien Jarno with the help of Jean Delvare This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* A few notes about the PCF8574: * The PCF8574 is an 8-bit I/O expander for the I2C bus produced by Philips Semiconductors. It is designed to provide a byte I2C interface to up to 8 separate devices. * The PCF8574 appears as a very simple SMBus device which can be read from or written to with SMBUS byte read/write accesses. --Dan */ #include #include #include #include /* Addresses to scan */ static unsigned short normal_i2c[] = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, I2C_CLIENT_END }; /* Insmod parameters */ I2C_CLIENT_INSMOD_2(pcf8574, pcf8574a); /* Initial values */ #define PCF8574_INIT 255 /* All outputs on (input mode) */ /* Each client has this additional data */ struct pcf8574_data { struct i2c_client client; u8 write; /* Remember last written value */ }; static int pcf8574_attach_adapter(struct i2c_adapter *adapter); static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind); static int pcf8574_detach_client(struct i2c_client *client); static void pcf8574_init_client(struct i2c_client *client); /* This is the driver that will be inserted */ static struct i2c_driver pcf8574_driver = { .driver = { .name = "pcf8574", }, .id = I2C_DRIVERID_PCF8574, .attach_adapter = pcf8574_attach_adapter, .detach_client = pcf8574_detach_client, }; /* following are the sysfs callback functions */ static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf) { struct i2c_client *client = to_i2c_client(dev); return sprintf(buf, "%u\n", i2c_smbus_read_byte(client)); } static DEVICE_ATTR(read, S_IRUGO, show_read, NULL); static ssize_t show_write(struct device *dev, struct device_attribute *attr, char *buf) { struct pcf8574_data *data = i2c_get_clientdata(to_i2c_client(dev)); return sprintf(buf, "%u\n", data->write); } static ssize_t set_write(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct i2c_client *client = to_i2c_client(dev); struct pcf8574_data *data = i2c_get_clientdata(client); unsigned long val = simple_strtoul(buf, NULL, 10); if (val > 0xff) return -EINVAL; data->write = val; i2c_smbus_write_byte(client, data->write); return count; } static DEVICE_ATTR(write, S_IWUSR | S_IRUGO, show_write, set_write); /* * Real code */ static int pcf8574_attach_adapter(struct i2c_adapter *adapter) { return i2c_probe(adapter, &addr_data, pcf8574_detect); } /* This function is called by i2c_probe */ static int pcf8574_detect(struct i2c_adapter *adapter, int address, int kind) { struct i2c_client *new_client; struct pcf8574_data *data; int err = 0; const char *client_name = ""; if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE)) goto exit; /* OK. For now, we presume we have a valid client. We now create the client structure, even though we cannot fill it completely yet. */ if (!(data = kzalloc(sizeof(struct pcf8574_data), GFP_KERNEL))) { err = -ENOMEM; goto exit; } new_client = &data->client; i2c_set_clientdata(new_client, data); new_client->addr = address; new_client->adapter = adapter; new_client->driver = &pcf8574_driver; new_client->flags = 0; /* Now, we would do the remaining detection. But the PCF8574 is plainly impossible to detect! Stupid chip. */ /* Determine the chip type */ if (kind <= 0) { if (address >= 0x38 && address <= 0x3f) kind = pcf8574a; else kind = pcf8574; } if (kind == pcf8574a) client_name = "pcf8574a"; else client_name = "pcf8574"; /* Fill in the remaining client fields and put it into the global list */ strlcpy(new_client->name, client_name, I2C_NAME_SIZE); /* Tell the I2C layer a new client has arrived */ if ((err = i2c_attach_client(new_client))) goto exit_free; /* Initialize the PCF8574 chip */ pcf8574_init_client(new_client); /* Register sysfs hooks */ device_create_file(&new_client->dev, &dev_attr_read); device_create_file(&new_client->dev, &dev_attr_write); return 0; /* OK, this is not exactly good programming practice, usually. But it is very code-efficient in this case. */ exit_free: kfree(data); exit: return err; } static int pcf8574_detach_client(struct i2c_client *client) { int err; if ((err = i2c_detach_client(client))) return err; kfree(i2c_get_clientdata(client)); return 0; } /* Called when we have found a new PCF8574. */ static void pcf8574_init_client(struct i2c_client *client) { struct pcf8574_data *data = i2c_get_clientdata(client); data->write = PCF8574_INIT; i2c_smbus_write_byte(client, data->write); } static int __init pcf8574_init(void) { return i2c_add_driver(&pcf8574_driver); } static void __exit pcf8574_exit(void) { i2c_del_driver(&pcf8574_driver); } MODULE_AUTHOR ("Frodo Looijaard , " "Philip Edelbrock , " "Dan Eaton " "and Aurelien Jarno "); MODULE_DESCRIPTION("PCF8574 driver"); MODULE_LICENSE("GPL"); module_init(pcf8574_init); module_exit(pcf8574_exit);