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
22static 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
54unsigned 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
115EXPORT_SYMBOL_GPL(fb_ddc_read);
116
117MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
118MODULE_DESCRIPTION("DDC/EDID reading support");
119MODULE_LICENSE("GPL");
120