drivers/char/i2c-parport.c

Name: Public Git Hosting - davej-history.git/blob - drivers/char/i2c-parport.c
Rating: 4.9 (114 reviews)
 1 /*
 2  * I2C driver for parallel port
 3  *
 4  * Author: Phil Blundell <philb@gnu.org>
 5  *
 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.
 10  *
 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:
 14  *
 15  * D0 clock out
 16  * D1 data out
 17  * BUSY data in
 18  */
 19
 20 #include <linux/parport.h>
 21 #include <linux/module.h>
 22 #include <linux/delay.h>
 23 #include <linux/i2c.h>
 24 #include <linux/init.h>
 25 #include <linux/spinlock.h>
 26
 27 #define I2C_DELAY 10
 28
 29 static int debug =0;
 30
 31 struct parport_i2c_bus
 32 {
 33 struct i2c_bus i2c;
 34 struct parport_i2c_bus *next;
 35 };
 36
 37 static struct parport_i2c_bus *bus_list;
 38
 39 static spinlock_t bus_list_lock = SPIN_LOCK_UNLOCKED;
 40
 41 /* software I2C functions */
 42
 43 static voidi2c_setlines(struct i2c_bus *bus,int clk,int data)
 44 {
 45 struct parport *p = bus->data;
 46 parport_write_data(p, (clk?1:0) | (data?2:0));
 47 udelay(I2C_DELAY);
 48 }
 49
 50 static inti2c_getdataline(struct i2c_bus *bus)
 51 {
 52 struct parport *p = bus->data;
 53 return(parport_read_status(p) & PARPORT_STATUS_BUSY) ?0:1;
 54 }
 55
 56 static struct i2c_bus parport_i2c_bus_template =
 57 {
 58 "...",
 59  I2C_BUSID_PARPORT,
 60  NULL,
 61
 62  SPIN_LOCK_UNLOCKED,
 63
 64  NULL,
 65  NULL,
 66
 67  i2c_setlines,
 68  i2c_getdataline,
 69  NULL,
 70  NULL,
 71 };
 72
 73 static voidi2c_parport_attach(struct parport *port)
 74 {
 75 struct parport_i2c_bus *b =kmalloc(sizeof(struct parport_i2c_bus),
 76  GFP_KERNEL);
 77  b->i2c = parport_i2c_bus_template;
 78  b->i2c.data = port;
 79 strncpy(b->i2c.name, port->name,32);
 80 spin_lock(&bus_list_lock);
 81  b->next = bus_list;
 82  bus_list = b;
 83 spin_unlock(&bus_list_lock);
 84 i2c_register_bus(&b->i2c);
 85 if(debug)
 86 printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
 87 }
 88
 89 static voidi2c_parport_detach(struct parport *port)
 90 {
 91 struct parport_i2c_bus *b, *old_b = NULL;
 92 spin_lock(&bus_list_lock);
 93  b = bus_list;
 94 while(b)
 95 {
 96 if(b->i2c.data == port)
 97 {
 98 if(old_b)
 99  old_b->next = b->next;
 100 else
 101  bus_list = b->next;
 102 i2c_unregister_bus(&b->i2c);
 103 kfree(b);
 104 break;
 105 }
 106  old_b = b;
 107  b = b->next;
 108 }
 109 spin_unlock(&bus_list_lock);
 110 if(debug)
 111 printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
 112 }
 113
 114 static struct parport_driver parport_i2c_driver =
 115 {
 116 "i2c",
 117  i2c_parport_attach,
 118  i2c_parport_detach
 119 };
 120
 121 #ifdef MODULE
 122 intinit_module(void)
 123 #else
 124 int __init i2c_parport_init(void)
 125 #endif
 126 {
 127 printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
 128 parport_register_driver(&parport_i2c_driver);
 129 return0;
 130 }
 131
 132 #ifdef MODULE
 133 MODULE_PARM(debug,"i");
 134
 135 voidcleanup_module(void)
 136 {
 137 struct parport_i2c_bus *b = bus_list;
 138 while(b)
 139 {
 140 struct parport_i2c_bus *next = b->next;
 141 i2c_unregister_bus(&b->i2c);
 142 kfree(b);
 143  b = next;
 144 }
 145 parport_unregister_driver(&parport_i2c_driver);
 146 }
 147 #endif