2 * I2C driver for parallel port
4 * Author: Phil Blundell <philb@gnu.org>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
11 * This driver implements a simple I2C protocol by bit-twiddling some
12 * signals on the parallel port. Since the outputs on the parallel port
13 * aren't open collector, three lines rather than two are used:
20 #include <linux/parport.h>
21 #include <linux/module.h>
22 #include <linux/delay.h>
23 #include <linux/i2c-old.h>
24 #include <linux/init.h>
25 #include <linux/spinlock.h>
31 struct parport_i2c_bus
34 struct parport_i2c_bus *next;
37 static struct parport_i2c_bus *bus_list;
39 static spinlock_t bus_list_lock = SPIN_LOCK_UNLOCKED;
41 /* software I2C functions */
43 static void i2c_setlines(struct i2c_bus *bus, int clk, int data)
45 struct parport *p = bus->data;
46 parport_write_data(p, (clk?1:0) | (data?2:0));
50 static int i2c_getdataline(struct i2c_bus *bus)
52 struct parport *p = bus->data;
53 return (parport_read_status(p) & PARPORT_STATUS_BUSY) ? 0 : 1;
56 static struct i2c_bus parport_i2c_bus_template =
73 static void i2c_parport_attach(struct parport *port)
75 struct parport_i2c_bus *b = kmalloc(sizeof(struct parport_i2c_bus),
78 printk(KERN_ERR "i2c_parport: Memory allocation failed. Not attaching.\n");
81 b->i2c = parport_i2c_bus_template;
82 b->i2c.data = parport_get_port (port);
83 strncpy(b->i2c.name, port->name, 32);
84 spin_lock(&bus_list_lock);
87 spin_unlock(&bus_list_lock);
88 i2c_register_bus(&b->i2c);
90 printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
93 static void i2c_parport_detach(struct parport *port)
95 struct parport_i2c_bus *b, *old_b = NULL;
96 spin_lock(&bus_list_lock);
100 if (b->i2c.data == port)
103 old_b->next = b->next;
106 i2c_unregister_bus(&b->i2c);
113 spin_unlock(&bus_list_lock);
115 printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
118 static struct parport_driver parport_i2c_driver =
126 int init_module(void)
128 int __init i2c_parport_init(void)
131 printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
132 parport_register_driver(&parport_i2c_driver);
137 MODULE_PARM(debug, "i");
139 void cleanup_module(void)
141 struct parport_i2c_bus *b = bus_list;
144 struct parport_i2c_bus *next = b->next;
145 i2c_unregister_bus(&b->i2c);
149 parport_unregister_driver(&parport_i2c_driver);
152 MODULE_LICENSE("GPL");