2 * driver/vide/fb_ddc.c - DDC/EDID read support.
4 * Copyright (C) 2006 Dennis Munsie <dmunsie@cecropia.com>
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
11 #include <linux/delay.h>
12 #include <linux/device.h>
14 #include <linux/i2c-algo-bit.h>
15 #include <linux/slab.h>
21 static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter
*adapter
)
23 unsigned char start
= 0x0;
24 unsigned char *buf
= kmalloc(EDID_LENGTH
, GFP_KERNEL
);
25 struct i2c_msg msgs
[] = {
40 dev_warn(&adapter
->dev
, "unable to allocate memory for EDID "
45 if (i2c_transfer(adapter
, msgs
, 2) == 2)
48 dev_warn(&adapter
->dev
, "unable to read EDID block.\n");
53 unsigned char *fb_ddc_read(struct i2c_adapter
*adapter
)
55 struct i2c_algo_bit_data
*algo_data
= adapter
->algo_data
;
56 unsigned char *edid
= NULL
;
59 algo_data
->setscl(algo_data
->data
, 1);
61 for (i
= 0; i
< 3; i
++) {
62 /* For some old monitors we need the
63 * following process to initialize/stop DDC
65 algo_data
->setsda(algo_data
->data
, 1);
68 algo_data
->setscl(algo_data
->data
, 1);
69 for (j
= 0; j
< 5; j
++) {
71 if (algo_data
->getscl(algo_data
->data
))
77 algo_data
->setsda(algo_data
->data
, 0);
79 algo_data
->setscl(algo_data
->data
, 0);
81 algo_data
->setsda(algo_data
->data
, 1);
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);
90 algo_data
->setscl(algo_data
->data
, 1);
91 for (j
= 0; j
< 10; j
++) {
93 if (algo_data
->getscl(algo_data
->data
))
97 algo_data
->setsda(algo_data
->data
, 1);
99 algo_data
->setscl(algo_data
->data
, 0);
100 algo_data
->setsda(algo_data
->data
, 0);
104 /* Release the DDC lines when done or the Apple Cinema HD display
107 algo_data
->setsda(algo_data
->data
, 1);
108 algo_data
->setscl(algo_data
->data
, 1);
110 adapter
->class |= I2C_CLASS_DDC
;
114 EXPORT_SYMBOL_GPL(fb_ddc_read
);
116 MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
117 MODULE_DESCRIPTION("DDC/EDID reading support");
118 MODULE_LICENSE("GPL");
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