xorg-server-1.4/hw/xfree86/ddc/edid.c

   1
   2 /* edid.c:  retrieve EDID record from raw DDC1 data stream: data
   3  * is contained in an array of unsigned int each unsigned int
   4  * contains one bit if bit is 0 unsigned int has to be zero else
   5  * unsigned int > 0
   6  *
   7  * Copyright 1998 by Egbert Eich <Egbert.Eich@Physik.TU-Darmstadt.DE>
   8  */
   9 #ifdef HAVE_XORG_CONFIG_H
  10 #include <xorg-config.h>
  11 #endif
  12
  13 #include "misc.h"
  14 #include "xf86.h"
  15 #include "xf86_OSproc.h"
  16 #include "xf86DDC.h"
  17 #include "ddcPriv.h"
  18 #include <string.h>
  19
  20 static int find_start(unsigned int *);
  21 static unsigned char * find_header(unsigned char *);
  22 static unsigned char * resort(unsigned char *);
  23
  24 unsigned char *
  25 GetEDID_DDC1(unsigned int *s_ptr)
  26 {
  27     unsigned char *d_block, *d_pos;
  28     unsigned int *s_pos, *s_end;
  29     int s_start;
  30     int i,j;
  31     s_start = find_start(s_ptr);
  32     if (s_start==-1) return NULL;
  33     s_end = s_ptr + NUM;
  34     s_pos = s_ptr + s_start;
  35     d_block=xalloc(EDID1_LEN);
  36     if (!d_block) return NULL;
  37     d_pos = d_block;
  38     for (i=0;i<EDID1_LEN;i++) {
  39         for (j=0;j<8;j++) {
  40             *d_pos <<= 1;
  41             if (*s_pos) {
  42                 *d_pos |= 0x01;
  43             }
  44             s_pos++; if (s_pos == s_end) s_pos=s_ptr;
  45         };
  46         s_pos++; if (s_pos == s_end) s_pos=s_ptr;
  47         d_pos++;
  48     }
  49     xfree(s_ptr);
  50     if (d_block && DDC_checksum(d_block,EDID1_LEN)) return NULL;
  51     return (resort(d_block));
  52 }
  53
  54 int
  55 DDC_checksum(unsigned char *block, int len)
  56 {
  57     int i, result = 0;
  58     int not_null = 0;
  59
  60     for (i=0;i<len;i++) {
  61         not_null |= block[i];
  62         result += block[i];
  63     }
  64
  65 #ifdef DEBUG
  66     if (result & 0xFF) ErrorF("DDC checksum not correct\n");
  67     if (!not_null) ErrorF("DDC read all Null\n");
  68 #endif
  69
  70     /* catch the trivial case where all bytes are 0 */
  71     if (!not_null) return 1;
  72
  73     return (result&0xFF);
  74 }
  75
  76 static int
  77 find_start(unsigned int *ptr)
  78 {
  79     unsigned int comp[9], test[9];
  80     int i,j;
  81
  82     for (i=0;i<9;i++){
  83         comp[i] = *(ptr++);
  84         test[i] = 1;
  85     }
  86     for (i=0;i<127;i++){
  87         for (j=0;j<9;j++){
  88             test[j] = test[j] & !(comp[j] ^ *(ptr++));
  89         }
  90     }
  91     for (i=0;i<9;i++)
  92         if (test[i]) return (i+1);
  93     return (-1);
  94 }
  95
  96 static unsigned char *
  97 find_header(unsigned char *block)
  98 {
  99     unsigned char *ptr, *head_ptr, *end;
 100     unsigned char header[]={0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00};
 101
 102     ptr = block;
 103     end = block + EDID1_LEN;
 104     while (ptr<end) {
 105         int i;
 106         head_ptr = ptr;
 107         for (i=0;i<8;i++){
 108             if (header[i] != *(head_ptr++)) break;
 109             if (head_ptr == end) head_ptr = block;
 110         }
 111         if (i==8) break;
 112         ptr++;
 113     }
 114     if (ptr == end) return (NULL);
 115     return (ptr);
 116 }
 117
 118 static unsigned char *
 119 resort(unsigned char *s_block)
 120 {
 121     unsigned char *d_new, *d_ptr, *d_end, *s_ptr, *s_end;
 122     unsigned char tmp;
 123
 124     s_end = s_block + EDID1_LEN;
 125     d_new = xalloc(EDID1_LEN);
 126     if (!d_new) return NULL;
 127     d_end = d_new + EDID1_LEN;
 128
 129     s_ptr = find_header(s_block);
 130     if (!s_ptr) return NULL;
 131     for (d_ptr=d_new;d_ptr<d_end;d_ptr++){
 132         tmp = *(s_ptr++);
 133         *d_ptr = tmp;
 134         if (s_ptr == s_end) s_ptr = s_block;
 135     }
 136     xfree(s_block);
 137     return (d_new);
 138 }
 139
 140