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