141 lines
3.0 KiB
C
141 lines
3.0 KiB
C
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/* edid.c: retrieve EDID record from raw DDC1 data stream: data
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* is contained in an array of unsigned int each unsigned int
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* contains one bit if bit is 0 unsigned int has to be zero else
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* unsigned int > 0
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*
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* Copyright 1998 by Egbert Eich <Egbert.Eich@Physik.TU-Darmstadt.DE>
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*/
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#ifdef HAVE_XORG_CONFIG_H
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#include <xorg-config.h>
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#endif
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#include "misc.h"
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#include "xf86.h"
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#include "xf86_OSproc.h"
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#include "xf86DDC.h"
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#include "ddcPriv.h"
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#include <string.h>
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static int find_start(unsigned int *);
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static unsigned char * find_header(unsigned char *);
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static unsigned char * resort(unsigned char *);
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unsigned char *
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GetEDID_DDC1(unsigned int *s_ptr)
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{
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unsigned char *d_block, *d_pos;
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unsigned int *s_pos, *s_end;
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int s_start;
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int i,j;
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s_start = find_start(s_ptr);
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if (s_start==-1) return NULL;
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s_end = s_ptr + NUM;
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s_pos = s_ptr + s_start;
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d_block=xalloc(EDID1_LEN);
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if (!d_block) return NULL;
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d_pos = d_block;
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for (i=0;i<EDID1_LEN;i++) {
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for (j=0;j<8;j++) {
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*d_pos <<= 1;
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if (*s_pos) {
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*d_pos |= 0x01;
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}
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s_pos++; if (s_pos == s_end) s_pos=s_ptr;
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};
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s_pos++; if (s_pos == s_end) s_pos=s_ptr;
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d_pos++;
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}
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xfree(s_ptr);
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if (d_block && DDC_checksum(d_block,EDID1_LEN)) return NULL;
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return (resort(d_block));
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}
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int
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DDC_checksum(unsigned char *block, int len)
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{
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int i, result = 0;
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int not_null = 0;
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for (i=0;i<len;i++) {
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not_null |= block[i];
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result += block[i];
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}
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#ifdef DEBUG
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if (result & 0xFF) ErrorF("DDC checksum not correct\n");
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if (!not_null) ErrorF("DDC read all Null\n");
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#endif
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/* catch the trivial case where all bytes are 0 */
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if (!not_null) return 1;
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return (result&0xFF);
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}
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static int
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find_start(unsigned int *ptr)
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{
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unsigned int comp[9], test[9];
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int i,j;
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for (i=0;i<9;i++){
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comp[i] = *(ptr++);
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test[i] = 1;
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}
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for (i=0;i<127;i++){
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for (j=0;j<9;j++){
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test[j] = test[j] & !(comp[j] ^ *(ptr++));
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}
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}
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for (i=0;i<9;i++)
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if (test[i]) return (i+1);
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return (-1);
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}
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static unsigned char *
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find_header(unsigned char *block)
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{
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unsigned char *ptr, *head_ptr, *end;
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unsigned char header[]={0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00};
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ptr = block;
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end = block + EDID1_LEN;
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while (ptr<end) {
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int i;
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head_ptr = ptr;
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for (i=0;i<8;i++){
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if (header[i] != *(head_ptr++)) break;
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if (head_ptr == end) head_ptr = block;
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}
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if (i==8) break;
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ptr++;
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}
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if (ptr == end) return (NULL);
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return (ptr);
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}
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static unsigned char *
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resort(unsigned char *s_block)
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{
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unsigned char *d_new, *d_ptr, *d_end, *s_ptr, *s_end;
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unsigned char tmp;
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s_end = s_block + EDID1_LEN;
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d_new = xalloc(EDID1_LEN);
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if (!d_new) return NULL;
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d_end = d_new + EDID1_LEN;
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s_ptr = find_header(s_block);
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if (!s_ptr) return NULL;
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for (d_ptr=d_new;d_ptr<d_end;d_ptr++){
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tmp = *(s_ptr++);
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*d_ptr = tmp;
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if (s_ptr == s_end) s_ptr = s_block;
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}
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xfree(s_block);
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return (d_new);
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}
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