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