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edid: Parse CTA-861 EDID extension

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This adds support for E-EDID extensions. Tags are allocated by VESA and
the CTA has such an extension defined in CTA-861.

The switch in `decode_ext_cta` is empty in this commit because we don't
parse any CTA-861 data blocks, yet.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2351>
This commit is contained in:
Sebastian Wick 2022-03-18 20:02:32 +01:00 committed by Jonas Ådahl
parent 97c0d17596
commit d76f9e6c4a
1 changed files with 101 additions and 8 deletions
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107
src/backends/edid-parse.c
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@ -31,6 +31,20 @@
#include "backends/edid.h"
/* VESA E-EDID */
#define EDID_BLOCK_LENGTH 128
#define EDID_EXT_FLAG_ADDR 0x7E
#define EDID_EXT_TAG_ADDR 0x00
/* VESA reserved IDs for extension blocks */
#define EDID_EXT_ID_CTA 0x02
/* CTA-861 extension block */
#define EDID_EXT_CTA_REVISION_ADDR 0x01
#define EDID_EXT_CTA_DESCRIPTOR_OFFSET_ADDR 0x02
#define EDID_EXT_CTA_DATA_BLOCK_OFFSET 0x04
#define EDID_EXT_CTA_TAG_EXTENDED 0x07
static int
get_bit (int in, int bit)
{
@ -45,6 +59,19 @@ get_bits (int in, int begin, int end)
return (in >> begin) & mask;
}
static void
decode_check_sum (const uint8_t *edid,
MetaEdidInfo *info)
{
int i;
uint8_t check = 0;
for (i = 0; i < 128; ++i)
check += edid[i];
info->checksum = check;
}
static gboolean
decode_header (const uint8_t *edid)
{
@ -527,17 +554,82 @@ decode_descriptors (const uint8_t *edid,
return TRUE;
}
static void
decode_check_sum (const uint8_t *edid,
static gboolean
decode_ext_cta (const uint8_t *cta_block,
MetaEdidInfo *info)
{
const uint8_t *data_block;
uint8_t data_block_end;
uint8_t data_block_offset;
int size;
int tag;
/* The CTA extension block is a number of data blocks followed by a number
* of (timing) descriptors. We only parse the data blocks. */
/* CTA-861-H Table 58: CTA Extension Version 3 */
data_block_end = cta_block[EDID_EXT_CTA_DESCRIPTOR_OFFSET_ADDR];
data_block_offset = EDID_EXT_CTA_DATA_BLOCK_OFFSET;
/* Table 58:
* If d=0, then no detailed timing descriptors are provided, and no data is
* provided in the data block collection */
if (data_block_end == 0)
return TRUE;
/* Table 58:
* If no data is provided in the data block collection, then d=4 */
if (data_block_end == 4)
return TRUE;
if (data_block_end < 4)
return FALSE;
while (data_block_offset < data_block_end)
{
/* CTA-861-H 7.4: CTA Data Block Collection */
data_block = cta_block + data_block_offset;
size = get_bits (data_block[0], 0, 4) + 1;
tag = get_bits (data_block[0], 5, 7);
data_block_offset += size;
/* CTA Data Block extended tag type is the second byte */
if (tag == EDID_EXT_CTA_TAG_EXTENDED)
tag = (tag << 8) + data_block[1];
switch (tag)
{
}
}
return TRUE;
}
static gboolean
decode_extensions (const uint8_t *edid,
MetaEdidInfo *info)
{
int blocks;
int i;
uint8_t check = 0;
const uint8_t *block = NULL;
for (i = 0; i < 128; ++i)
check += edid[i];
blocks = edid[EDID_EXT_FLAG_ADDR];
info->checksum = check;
for (i = 0; i < blocks; i++)
{
block = edid + EDID_BLOCK_LENGTH * (i + 1);
switch (block[EDID_EXT_TAG_ADDR])
{
case EDID_EXT_ID_CTA:
if (!decode_ext_cta (block, info))
return FALSE;
break;
}
}
return TRUE;
}
MetaEdidInfo *
@ -556,7 +648,8 @@ meta_edid_info_new_parse (const uint8_t *edid)
&& decode_color_characteristics (edid, info)
&& decode_established_timings (edid, info)
&& decode_standard_timings (edid, info)
&& decode_descriptors (edid, info))
&& decode_descriptors (edid, info)
&& decode_extensions (edid, info))
{
return info;
}