LXR linux/drivers/video/fb

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