/* * 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/export.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.\n");		return NULL;	} 	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); 	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);		if (algo_data->getscl) {			for (j = 0; j < 5; j++) {				msleep(10);				if (algo_data->getscl(algo_data->data))					break;			}			if (j == 5)				continue;		} else {			udelay(algo_data->udelay);		} 		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);		if (algo_data->getscl) {			for (j = 0; j < 10; j++) {				msleep(10);				if (algo_data->getscl(algo_data->data))					break;			}		} else {			udelay(algo_data->udelay);		} 		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); 	return edid;} EXPORT_SYMBOL_GPL(fb_ddc_read); MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");MODULE_DESCRIPTION("DDC/EDID reading support");MODULE_LICENSE("GPL");