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/export.h>
14 #include <linux/module.h>
15 #include <linux/fb.h>
16 #include <linux/i2c-algo-bit.h>
17 #include <linux/slab.h>
18
19 #include "../edid.h"
20
21 #define DDC_ADDR 0x50
22
fb_do_probe_ddc_edid(struct i2c_adapter * adapter)23 static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
24 {
25 unsigned char start = 0x0;
26 unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
27 struct i2c_msg msgs[] = {
28 {
29 .addr = DDC_ADDR,
30 .flags = 0,
31 .len = 1,
32 .buf = &start,
33 }, {
34 .addr = DDC_ADDR,
35 .flags = I2C_M_RD,
36 .len = EDID_LENGTH,
37 .buf = buf,
38 }
39 };
40
41 if (!buf) {
42 dev_warn(&adapter->dev, "unable to allocate memory for EDID "
43 "block.\n");
44 return NULL;
45 }
46
47 if (i2c_transfer(adapter, msgs, 2) == 2)
48 return buf;
49
50 dev_warn(&adapter->dev, "unable to read EDID block.\n");
51 kfree(buf);
52 return NULL;
53 }
54
fb_ddc_read(struct i2c_adapter * adapter)55 unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
56 {
57 struct i2c_algo_bit_data *algo_data = adapter->algo_data;
58 unsigned char *edid = NULL;
59 int i, j;
60
61 algo_data->setscl(algo_data->data, 1);
62
63 for (i = 0; i < 3; i++) {
64 /* For some old monitors we need the
65 * following process to initialize/stop DDC
66 */
67 algo_data->setsda(algo_data->data, 1);
68 msleep(13);
69
70 algo_data->setscl(algo_data->data, 1);
71 if (algo_data->getscl) {
72 for (j = 0; j < 5; j++) {
73 msleep(10);
74 if (algo_data->getscl(algo_data->data))
75 break;
76 }
77 if (j == 5)
78 continue;
79 } else {
80 udelay(algo_data->udelay);
81 }
82
83 algo_data->setsda(algo_data->data, 0);
84 msleep(15);
85 algo_data->setscl(algo_data->data, 0);
86 msleep(15);
87 algo_data->setsda(algo_data->data, 1);
88 msleep(15);
89
90 /* Do the real work */
91 edid = fb_do_probe_ddc_edid(adapter);
92 algo_data->setsda(algo_data->data, 0);
93 algo_data->setscl(algo_data->data, 0);
94 msleep(15);
95
96 algo_data->setscl(algo_data->data, 1);
97 if (algo_data->getscl) {
98 for (j = 0; j < 10; j++) {
99 msleep(10);
100 if (algo_data->getscl(algo_data->data))
101 break;
102 }
103 } else {
104 udelay(algo_data->udelay);
105 }
106
107 algo_data->setsda(algo_data->data, 1);
108 msleep(15);
109 algo_data->setscl(algo_data->data, 0);
110 algo_data->setsda(algo_data->data, 0);
111 if (edid)
112 break;
113 }
114 /* Release the DDC lines when done or the Apple Cinema HD display
115 * will switch off
116 */
117 algo_data->setsda(algo_data->data, 1);
118 algo_data->setscl(algo_data->data, 1);
119
120 return edid;
121 }
122
123 EXPORT_SYMBOL_GPL(fb_ddc_read);
124
125 MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
126 MODULE_DESCRIPTION("DDC/EDID reading support");
127 MODULE_LICENSE("GPL");
128