1 /*
2 * drivers/video/fb_ddc.c - DDC/EDID read support.
3 *
4 * Copyright (C) 2006 Dennis Munsie <dmunsie@cecropia.com>
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file COPYING in the main directory of this archive
8 * for more details.
9 */
10
11 #include <linux/delay.h>
12 #include <linux/device.h>
13 #include <linux/module.h>
14 #include <linux/fb.h>
15 #include <linux/i2c-algo-bit.h>
16 #include <linux/slab.h>
17
18 #include "edid.h"
19
20 #define DDC_ADDR 0x50
21
fb_do_probe_ddc_edid(struct i2c_adapter * adapter)22 static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
23 {
24 unsigned char start = 0x0;
25 unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
26 struct i2c_msg msgs[] = {
27 {
28 .addr = DDC_ADDR,
29 .flags = 0,
30 .len = 1,
31 .buf = &start,
32 }, {
33 .addr = DDC_ADDR,
34 .flags = I2C_M_RD,
35 .len = EDID_LENGTH,
36 .buf = buf,
37 }
38 };
39
40 if (!buf) {
41 dev_warn(&adapter->dev, "unable to allocate memory for EDID "
42 "block.\n");
43 return NULL;
44 }
45
46 if (i2c_transfer(adapter, msgs, 2) == 2)
47 return buf;
48
49 dev_warn(&adapter->dev, "unable to read EDID block.\n");
50 kfree(buf);
51 return NULL;
52 }
53
fb_ddc_read(struct i2c_adapter * adapter)54 unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
55 {
56 struct i2c_algo_bit_data *algo_data = adapter->algo_data;
57 unsigned char *edid = NULL;
58 int i, j;
59
60 algo_data->setscl(algo_data->data, 1);
61
62 for (i = 0; i < 3; i++) {
63 /* For some old monitors we need the
64 * following process to initialize/stop DDC
65 */
66 algo_data->setsda(algo_data->data, 1);
67 msleep(13);
68
69 algo_data->setscl(algo_data->data, 1);
70 for (j = 0; j < 5; j++) {
71 msleep(10);
72 if (algo_data->getscl(algo_data->data))
73 break;
74 }
75 if (j == 5)
76 continue;
77
78 algo_data->setsda(algo_data->data, 0);
79 msleep(15);
80 algo_data->setscl(algo_data->data, 0);
81 msleep(15);
82 algo_data->setsda(algo_data->data, 1);
83 msleep(15);
84
85 /* Do the real work */
86 edid = fb_do_probe_ddc_edid(adapter);
87 algo_data->setsda(algo_data->data, 0);
88 algo_data->setscl(algo_data->data, 0);
89 msleep(15);
90
91 algo_data->setscl(algo_data->data, 1);
92 for (j = 0; j < 10; j++) {
93 msleep(10);
94 if (algo_data->getscl(algo_data->data))
95 break;
96 }
97
98 algo_data->setsda(algo_data->data, 1);
99 msleep(15);
100 algo_data->setscl(algo_data->data, 0);
101 algo_data->setsda(algo_data->data, 0);
102 if (edid)
103 break;
104 }
105 /* Release the DDC lines when done or the Apple Cinema HD display
106 * will switch off
107 */
108 algo_data->setsda(algo_data->data, 1);
109 algo_data->setscl(algo_data->data, 1);
110
111 adapter->class |= I2C_CLASS_DDC;
112 return edid;
113 }
114
115 EXPORT_SYMBOL_GPL(fb_ddc_read);
116
117 MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
118 MODULE_DESCRIPTION("DDC/EDID reading support");
119 MODULE_LICENSE("GPL");
120