/*

   * drivers/video/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/module.h>

  #include <linux/fb.h>
  #include <linux/i2c-algo-bit.h>

  #include <linux/slab.h>

  
  #include "edid.h"
  
  #define DDC_ADDR	0x50
  
  static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
  {
  	unsigned char start = 0x0;

  	unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL);

  	struct i2c_msg msgs[] = {
  		{
  			.addr	= DDC_ADDR,

  			.flags	= 0,

  			.len	= 1,
  			.buf	= &start,
  		}, {
  			.addr	= DDC_ADDR,
  			.flags	= I2C_M_RD,
  			.len	= EDID_LENGTH,

  			.buf	= buf,

  		}
  	};

  	if (!buf) {
  		dev_warn(&adapter->dev, "unable to allocate memory for EDID "
  			 "block.
  ");
  		return NULL;
  	}

  
  	if (i2c_transfer(adapter, msgs, 2) == 2)
  		return buf;
  
  	dev_warn(&adapter->dev, "unable to read EDID block.
  ");
  	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);

  
  	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, 1);

  		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);

  		algo_data->setsda(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, 1);
  	algo_data->setscl(algo_data->data, 1);

  	adapter->class |= I2C_CLASS_DDC;

  	return edid;
  }
  
  EXPORT_SYMBOL_GPL(fb_ddc_read);
  
  MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
  MODULE_DESCRIPTION("DDC/EDID reading support");
  MODULE_LICENSE("GPL");