File: /usr/src/linux/drivers/media/video/i2c-parport.c
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-old.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 void i2c_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 int i2c_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 void i2c_parport_attach(struct parport *port)
74 {
75 struct parport_i2c_bus *b = kmalloc(sizeof(struct parport_i2c_bus),
76 GFP_KERNEL);
77 if (!b) {
78 printk(KERN_ERR "i2c_parport: Memory allocation failed. Not attaching.\n");
79 return;
80 }
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);
85 b->next = bus_list;
86 bus_list = b;
87 spin_unlock(&bus_list_lock);
88 i2c_register_bus(&b->i2c);
89 if (debug)
90 printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
91 }
92
93 static void i2c_parport_detach(struct parport *port)
94 {
95 struct parport_i2c_bus *b, *old_b = NULL;
96 spin_lock(&bus_list_lock);
97 b = bus_list;
98 while (b)
99 {
100 if (b->i2c.data == port)
101 {
102 if (old_b)
103 old_b->next = b->next;
104 else
105 bus_list = b->next;
106 i2c_unregister_bus(&b->i2c);
107 kfree(b);
108 break;
109 }
110 old_b = b;
111 b = b->next;
112 }
113 spin_unlock(&bus_list_lock);
114 if (debug)
115 printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
116 }
117
118 static struct parport_driver parport_i2c_driver =
119 {
120 "i2c",
121 i2c_parport_attach,
122 i2c_parport_detach
123 };
124
125 #ifdef MODULE
126 int init_module(void)
127 #else
128 int __init i2c_parport_init(void)
129 #endif
130 {
131 printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
132 parport_register_driver(&parport_i2c_driver);
133 return 0;
134 }
135
136 #ifdef MODULE
137 MODULE_PARM(debug, "i");
138
139 void cleanup_module(void)
140 {
141 struct parport_i2c_bus *b = bus_list;
142 while (b)
143 {
144 struct parport_i2c_bus *next = b->next;
145 i2c_unregister_bus(&b->i2c);
146 kfree(b);
147 b = next;
148 }
149 parport_unregister_driver(&parport_i2c_driver);
150 }
151 #endif
152