LXR linux/drivers/video/fbdev/core/fb

   1/*
   2 * drivers/video/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/module.h>
  14#include <linux/fb.h>
  15#include <linux/i2c-algo-bit.h>
  16#include <linux/slab.h>
  17
  18#include "../edid.h"
  19
  20#define DDC_ADDR        0x50
  21
  22static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter)
  23{
  24        unsigned char start = 0x0;
  25        unsigned char *buf = kmalloc(EDID_LENGTH, GFP_KERNEL);
  26        struct i2c_msg msgs[] = {
  27                {
  28                        .addr   = DDC_ADDR,
  29                        .flags  = 0,
  30                        .len    = 1,
  31                        .buf    = &start,
  32                }, {
  33                        .addr   = DDC_ADDR,
  34                        .flags  = I2C_M_RD,
  35                        .len    = EDID_LENGTH,
  36                        .buf    = buf,
  37                }
  38        };
  39
  40        if (!buf) {
  41                dev_warn(&adapter->dev, "unable to allocate memory for EDID "
  42                         "block.\n");
  43                return NULL;
  44        }
  45
  46        if (i2c_transfer(adapter, msgs, 2) == 2)
  47                return buf;
  48
  49        dev_warn(&adapter->dev, "unable to read EDID block.\n");
  50        kfree(buf);
  51        return NULL;
  52}
  53
  54unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
  55{
  56        struct i2c_algo_bit_data *algo_data = adapter->algo_data;
  57        unsigned char *edid = NULL;
  58        int i, j;
  59
  60        algo_data->setscl(algo_data->data, 1);
  61
  62        for (i = 0; i < 3; i++) {
  63                /* For some old monitors we need the
  64                 * following process to initialize/stop DDC
  65                 */
  66                algo_data->setsda(algo_data->data, 1);
  67                msleep(13);
  68
  69                algo_data->setscl(algo_data->data, 1);
  70                if (algo_data->getscl) {
  71                        for (j = 0; j < 5; j++) {
  72                                msleep(10);
  73                                if (algo_data->getscl(algo_data->data))
  74                                        break;
  75                        }
  76                        if (j == 5)
  77                                continue;
  78                } else {
  79                        udelay(algo_data->udelay);
  80                }
  81
  82                algo_data->setsda(algo_data->data, 0);
  83                msleep(15);
  84                algo_data->setscl(algo_data->data, 0);
  85                msleep(15);
  86                algo_data->setsda(algo_data->data, 1);
  87                msleep(15);
  88
  89                /* Do the real work */
  90                edid = fb_do_probe_ddc_edid(adapter);
  91                algo_data->setsda(algo_data->data, 0);
  92                algo_data->setscl(algo_data->data, 0);
  93                msleep(15);
  94
  95                algo_data->setscl(algo_data->data, 1);
  96                if (algo_data->getscl) {
  97                        for (j = 0; j < 10; j++) {
  98                                msleep(10);
  99                                if (algo_data->getscl(algo_data->data))
 100                                        break;
 101                        }
 102                } else {
 103                        udelay(algo_data->udelay);
 104                }
 105
 106                algo_data->setsda(algo_data->data, 1);
 107                msleep(15);
 108                algo_data->setscl(algo_data->data, 0);
 109                algo_data->setsda(algo_data->data, 0);
 110                if (edid)
 111                        break;
 112        }
 113        /* Release the DDC lines when done or the Apple Cinema HD display
 114         * will switch off
 115         */
 116        algo_data->setsda(algo_data->data, 1);
 117        algo_data->setscl(algo_data->data, 1);
 118
 119        adapter->class |= I2C_CLASS_DDC;
 120        return edid;
 121}
 122
 123EXPORT_SYMBOL_GPL(fb_ddc_read);
 124
 125MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>");
 126MODULE_DESCRIPTION("DDC/EDID reading support");
 127MODULE_LICENSE("GPL");
 128