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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 | |
21 | static 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 | |
53 | unsigned 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 | |
114 | EXPORT_SYMBOL_GPL(fb_ddc_read); |
115 | |
116 | MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>"); |
117 | MODULE_DESCRIPTION("DDC/EDID reading support"); |
118 | MODULE_LICENSE("GPL"); |
119 |
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