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/*
* I2C driver for parallel port
*
* Author: Phil Blundell <philb@gnu.org>
*
* 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 driver implements a simple I2C protocol by bit-twiddling some
* signals on the parallel port. Since the outputs on the parallel port
* aren't open collector, three lines rather than two are used:
*
* D0 clock out
* D1 data out
* BUSY data in
*/
#include <linux/parport.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#define I2C_DELAY 10
static int debug = 0;
struct parport_i2c_bus
{
struct i2c_bus i2c;
struct parport_i2c_bus *next;
};
static struct parport_i2c_bus *bus_list;
static spinlock_t bus_list_lock = SPIN_LOCK_UNLOCKED;
/* software I2C functions */
static void i2c_setlines(struct i2c_bus *bus, int clk, int data)
{
struct parport *p = bus->data;
parport_write_data(p, (clk?1:0) | (data?2:0));
udelay(I2C_DELAY);
}
static int i2c_getdataline(struct i2c_bus *bus)
{
struct parport *p = bus->data;
return (parport_read_status(p) & PARPORT_STATUS_BUSY) ? 0 : 1;
}
static struct i2c_bus parport_i2c_bus_template =
{
"...",
I2C_BUSID_PARPORT,
NULL,
SPIN_LOCK_UNLOCKED,
NULL,
NULL,
i2c_setlines,
i2c_getdataline,
NULL,
NULL,
};
static void i2c_parport_attach(struct parport *port)
{
struct parport_i2c_bus *b = kmalloc(sizeof(struct parport_i2c_bus),
GFP_KERNEL);
b->i2c = parport_i2c_bus_template;
b->i2c.data = port;
strncpy(b->i2c.name, port->name, 32);
spin_lock(&bus_list_lock);
b->next = bus_list;
bus_list = b;
spin_unlock(&bus_list_lock);
i2c_register_bus(&b->i2c);
if (debug)
printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
}
static void i2c_parport_detach(struct parport *port)
{
struct parport_i2c_bus *b, *old_b = NULL;
spin_lock(&bus_list_lock);
b = bus_list;
while (b)
{
if (b->i2c.data == port)
{
if (old_b)
old_b->next = b->next;
else
bus_list = b->next;
i2c_unregister_bus(&b->i2c);
kfree(b);
break;
}
old_b = b;
b = b->next;
}
spin_unlock(&bus_list_lock);
if (debug)
printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
}
static struct parport_driver parport_i2c_driver =
{
"i2c",
i2c_parport_attach,
i2c_parport_detach
};
#ifdef MODULE
int init_module(void)
#else
int __init i2c_parport_init(void)
#endif
{
printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
parport_register_driver(&parport_i2c_driver);
return 0;
}
#ifdef MODULE
MODULE_PARM(debug, "i");
void cleanup_module(void)
{
struct parport_i2c_bus *b = bus_list;
while (b)
{
struct parport_i2c_bus *next = b->next;
i2c_unregister_bus(&b->i2c);
kfree(b);
b = next;
}
parport_unregister_driver(&parport_i2c_driver);
}
#endif
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