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ad1e3f4167
Introduce an opaque struct di_edid to host EDID structures. Add a function to create a di_edid (with basic size, header and checksum validation). Add functions to fetch the EDID version and revision. This doesn't do much, but hopefully can be used as a fundation. Signed-off-by: Simon Ser <contact@emersion.fr>
101 lines
1.8 KiB
C
101 lines
1.8 KiB
C
#include <errno.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include "edid.h"
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/**
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* The size of an EDID block, defined in section 2.2.
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*/
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#define EDID_BLOCK_SIZE 128
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/**
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* The maximum number of EDID blocks (including the base block), defined in
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* section 2.2.1.
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*/
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#define EDID_MAX_BLOCK_COUNT 256
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/**
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* Fixed EDID header, defined in section 3.1.
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*/
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static const uint8_t header[] = { 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00 };
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static void
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parse_version_revision(const uint8_t data[static EDID_BLOCK_SIZE],
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int *version, int *revision)
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{
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*version = (int) data[18];
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*revision = (int) data[19];
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}
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static bool
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validate_block_checksum(const uint8_t data[static EDID_BLOCK_SIZE])
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{
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uint8_t sum = 0;
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size_t i;
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for (i = 0; i < EDID_BLOCK_SIZE; i++) {
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sum += data[i];
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}
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return sum == 0;
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}
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struct di_edid *
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di_edid_parse(const void *data, size_t size)
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{
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struct di_edid *edid;
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int version, revision;
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if (size < EDID_BLOCK_SIZE ||
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size > EDID_MAX_BLOCK_COUNT * EDID_BLOCK_SIZE) {
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errno = EINVAL;
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return NULL;
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}
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if (memcmp(data, header, sizeof(header)) != 0) {
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errno = EINVAL;
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return NULL;
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}
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parse_version_revision(data, &version, &revision);
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if (version != 1) {
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/* Only EDID version 1 is supported -- as per section 2.1.7
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* subsequent versions break the structure */
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errno = ENOTSUP;
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return NULL;
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}
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if (!validate_block_checksum(data)) {
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errno = EINVAL;
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return NULL;
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}
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edid = calloc(1, sizeof(*edid));
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if (!edid) {
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return NULL;
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}
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edid->version = version;
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edid->revision = revision;
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return edid;
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}
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void
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di_edid_destroy(struct di_edid *edid)
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{
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free(edid);
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}
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int
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di_edid_get_version(const struct di_edid *edid)
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{
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return edid->version;
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}
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int
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di_edid_get_revision(const struct di_edid *edid)
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{
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return edid->revision;
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}
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