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authorDennis Munsie <dmunsie@cecropia.com>2006-10-03 04:14:42 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-03 11:04:09 -0400
commitfc5891c8a3ba284f13994d7bc1f1bfa8283982de (patch)
treea9361f04236b60e0c1a8b1158e490b505c0961f4 /drivers/video/fb_ddc.c
parent66cf75121b1c8128ef9ab2d772c5654ae00c4284 (diff)
[PATCH] fbdev: Add generic ddc read functionality
Adds functionality to read the EDID information over the DDC bus in a generic way. This code is based on the DDC implementation in the radeon driver. [adaplas] - separate from fbmon.c and place in new file fb_ddc.c - remove dependency to CONFIG_I2C and CONFIG_I2C_ALGOBIT, otherwise, feature will not compile if i2c support is compiled as a module - feature is selectable only by drivers needing it. It must have a 'select FB_DDC if xxx' in Kconfig - change printk's to dev_*, the i2c people prefers it Signed-off-by: Dennis Munsie <dmunsie@cecropia.com> Signed-off-by: Antonino Daplas <adaplas@pol.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/video/fb_ddc.c')
-rw-r--r--drivers/video/fb_ddc.c116
1 files changed, 116 insertions, 0 deletions
diff --git a/drivers/video/fb_ddc.c b/drivers/video/fb_ddc.c
new file mode 100644
index 000000000000..3aa6ebf68f17
--- /dev/null
+++ b/drivers/video/fb_ddc.c
@@ -0,0 +1,116 @@
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
20static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
21{
22 unsigned char start = 0x0;
23 struct i2c_msg msgs[] = {
24 {
25 .addr = DDC_ADDR,
26 .len = 1,
27 .buf = &start,
28 }, {
29 .addr = DDC_ADDR,
30 .flags = I2C_M_RD,
31 .len = EDID_LENGTH,
32 }
33 };
34 unsigned char *buf;
35
36 buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
37 if (!buf) {
38 dev_warn(&adapter->dev, "unable to allocate memory for EDID "
39 "block.\n");
40 return NULL;
41 }
42 msgs[1].buf = buf;
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
52unsigned 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);
59 algo_data->setscl(algo_data->data, 0);
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, 0);
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 if (edid)
101 break;
102 }
103 /* Release the DDC lines when done or the Apple Cinema HD display
104 * will switch off
105 */
106 algo_data->setsda(algo_data->data, 0);
107 algo_data->setscl(algo_data->data, 0);
108
109 return edid;
110}
111
112EXPORT_SYMBOL_GPL(fb_ddc_read);
113
114MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
115MODULE_DESCRIPTION("DDC/EDID reading support");
116MODULE_LICENSE("GPL");