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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 | |
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 | |
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 |
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