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/*
* driver/vide/fb_ddc.c - DDC/EDID read support.
*
* Copyright (C) 2006 Dennis Munsie <dmunsie@cecropia.com>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*/
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fb.h>
#include <linux/i2c-algo-bit.h>
#include "edid.h"
#define DDC_ADDR 0x50
static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
{
unsigned char start = 0x0;
struct i2c_msg msgs[] = {
{
.addr = DDC_ADDR,
.len = 1,
.buf = &start,
}, {
.addr = DDC_ADDR,
.flags = I2C_M_RD,
.len = EDID_LENGTH,
}
};
unsigned char *buf;
buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
if (!buf) {
dev_warn(&adapter->dev, "unable to allocate memory for EDID "
"block.\n");
return NULL;
}
msgs[1].buf = buf;
if (i2c_transfer(adapter, msgs, 2) == 2)
return buf;
dev_warn(&adapter->dev, "unable to read EDID block.\n");
kfree(buf);
return NULL;
}
unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
{
struct i2c_algo_bit_data *algo_data = adapter->algo_data;
unsigned char *edid = NULL;
int i, j;
algo_data->setscl(algo_data->data, 1);
algo_data->setscl(algo_data->data, 0);
for (i = 0; i < 3; i++) {
/* For some old monitors we need the
* following process to initialize/stop DDC
*/
algo_data->setsda(algo_data->data, 0);
msleep(13);
algo_data->setscl(algo_data->data, 1);
for (j = 0; j < 5; j++) {
msleep(10);
if (algo_data->getscl(algo_data->data))
break;
}
if (j == 5)
continue;
algo_data->setsda(algo_data->data, 0);
msleep(15);
algo_data->setscl(algo_data->data, 0);
msleep(15);
algo_data->setsda(algo_data->data, 1);
msleep(15);
/* Do the real work */
edid = fb_do_probe_ddc_edid(adapter);
algo_data->setsda(algo_data->data, 0);
algo_data->setscl(algo_data->data, 0);
msleep(15);
algo_data->setscl(algo_data->data, 1);
for (j = 0; j < 10; j++) {
msleep(10);
if (algo_data->getscl(algo_data->data))
break;
}
algo_data->setsda(algo_data->data, 1);
msleep(15);
algo_data->setscl(algo_data->data, 0);
if (edid)
break;
}
/* Release the DDC lines when done or the Apple Cinema HD display
* will switch off
*/
algo_data->setsda(algo_data->data, 0);
algo_data->setscl(algo_data->data, 0);
return edid;
}
EXPORT_SYMBOL_GPL(fb_ddc_read);
MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
MODULE_DESCRIPTION("DDC/EDID reading support");
MODULE_LICENSE("GPL");
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