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fc5891c8 DM |
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 | ||
16 | #include "edid.h" | |
17 | ||
18 | #define DDC_ADDR 0x50 | |
19 | ||
20 | static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter) | |
21 | { | |
22 | unsigned char start = 0x0; | |
4be70390 | 23 | unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL); |
fc5891c8 DM |
24 | struct i2c_msg msgs[] = { |
25 | { | |
26 | .addr = DDC_ADDR, | |
4be70390 | 27 | .flags = 0, |
fc5891c8 DM |
28 | .len = 1, |
29 | .buf = &start, | |
30 | }, { | |
31 | .addr = DDC_ADDR, | |
32 | .flags = I2C_M_RD, | |
33 | .len = EDID_LENGTH, | |
4be70390 | 34 | .buf = buf, |
fc5891c8 DM |
35 | } |
36 | }; | |
fc5891c8 | 37 | |
fc5891c8 DM |
38 | if (!buf) { |
39 | dev_warn(&adapter->dev, "unable to allocate memory for EDID " | |
40 | "block.\n"); | |
41 | return NULL; | |
42 | } | |
fc5891c8 DM |
43 | |
44 | if (i2c_transfer(adapter, msgs, 2) == 2) | |
45 | return buf; | |
46 | ||
47 | dev_warn(&adapter->dev, "unable to read EDID block.\n"); | |
48 | kfree(buf); | |
49 | return NULL; | |
50 | } | |
51 | ||
52 | unsigned char *fb_ddc_read(struct i2c_adapter *adapter) | |
53 | { | |
54 | struct i2c_algo_bit_data *algo_data = adapter->algo_data; | |
55 | unsigned char *edid = NULL; | |
56 | int i, j; | |
57 | ||
58 | algo_data->setscl(algo_data->data, 1); | |
fc5891c8 DM |
59 | |
60 | for (i = 0; i < 3; i++) { | |
61 | /* For some old monitors we need the | |
62 | * following process to initialize/stop DDC | |
63 | */ | |
b64d7082 | 64 | algo_data->setsda(algo_data->data, 1); |
fc5891c8 DM |
65 | msleep(13); |
66 | ||
67 | algo_data->setscl(algo_data->data, 1); | |
68 | for (j = 0; j < 5; j++) { | |
69 | msleep(10); | |
70 | if (algo_data->getscl(algo_data->data)) | |
71 | break; | |
72 | } | |
73 | if (j == 5) | |
74 | continue; | |
75 | ||
76 | algo_data->setsda(algo_data->data, 0); | |
77 | msleep(15); | |
78 | algo_data->setscl(algo_data->data, 0); | |
79 | msleep(15); | |
80 | algo_data->setsda(algo_data->data, 1); | |
81 | msleep(15); | |
82 | ||
83 | /* Do the real work */ | |
84 | edid = fb_do_probe_ddc_edid(adapter); | |
85 | algo_data->setsda(algo_data->data, 0); | |
86 | algo_data->setscl(algo_data->data, 0); | |
87 | msleep(15); | |
88 | ||
89 | algo_data->setscl(algo_data->data, 1); | |
90 | for (j = 0; j < 10; j++) { | |
91 | msleep(10); | |
92 | if (algo_data->getscl(algo_data->data)) | |
93 | break; | |
94 | } | |
95 | ||
96 | algo_data->setsda(algo_data->data, 1); | |
97 | msleep(15); | |
98 | algo_data->setscl(algo_data->data, 0); | |
b64d7082 | 99 | algo_data->setsda(algo_data->data, 0); |
fc5891c8 DM |
100 | if (edid) |
101 | break; | |
102 | } | |
103 | /* Release the DDC lines when done or the Apple Cinema HD display | |
104 | * will switch off | |
105 | */ | |
b64d7082 JD |
106 | algo_data->setsda(algo_data->data, 1); |
107 | algo_data->setscl(algo_data->data, 1); | |
fc5891c8 | 108 | |
c1b6b4f2 | 109 | adapter->class |= I2C_CLASS_DDC; |
fc5891c8 DM |
110 | return edid; |
111 | } | |
112 | ||
113 | EXPORT_SYMBOL_GPL(fb_ddc_read); | |
114 | ||
115 | MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>"); | |
116 | MODULE_DESCRIPTION("DDC/EDID reading support"); | |
117 | MODULE_LICENSE("GPL"); |