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lib/edid: Update the condition check for extension block count

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According to E-EDID A.2_revised_2020.pdf, block maps are optional in
EDID 1.4. If block maps are used then 254 is the maximum number.
Otherwise, 255 is the maximum number. For now, we simply print the
number of extension blocks.

BUG=b:392040003
BRANCH=rauru
TEST=Verify with the panel containing two EDID extension blocks

Change-Id: I2458e3493e74f91af6422b36285bb95e438a29f1
Signed-off-by: Yidi Lin <yidilin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86723
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
This commit is contained in:
Yidi Lin 2025-03-05 17:03:45 +08:00 • committed by Matt DeVillier
commit 339d1a26ad
1 changed files with 6 additions and 14 deletions
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20
src/lib/edid.c
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@ -32,7 +32,6 @@ struct edid_context {
int has_valid_week;
int has_valid_year;
int has_valid_detailed_blocks;
int has_valid_extension_count;
int has_valid_descriptor_ordering;
int has_valid_descriptor_pad;
int has_valid_range_descriptor;
@ -1444,15 +1443,12 @@ int decode_edid(unsigned char *edid, int size, struct edid *out)
}
}
/* check this, 1.4 verification guide says otherwise */
if (edid[0x7e]) {
printk(BIOS_SPEW, "Has %d extension blocks\n", edid[0x7e]);
/* 2 is impossible because of the block map */
if (edid[0x7e] != 2)
c.has_valid_extension_count = 1;
} else {
c.has_valid_extension_count = 1;
}
/* According to E-EDID A.2_revised_2020.pdf, block maps are optional
* in EDID 1.4. If block maps are used then 254 is the maximum number.
* Otherwise, 255 is the maximum number. For now, we simply print the
* number of extension blocks.
*/
printk(BIOS_SPEW, "Has %d extension blocks\n", edid[0x7e]);
printk(BIOS_SPEW, "Checksum\n");
c.has_valid_checksum = do_checksum(edid);
@ -1558,7 +1554,6 @@ int decode_edid(unsigned char *edid, int size, struct edid *out)
!c.has_valid_week ||
!c.has_valid_detailed_blocks ||
!c.has_valid_dummy_block ||
!c.has_valid_extension_count ||
!c.has_valid_descriptor_ordering ||
!c.has_valid_range_descriptor ||
!c.manufacturer_name_well_formed) {
@ -1581,9 +1576,6 @@ int decode_edid(unsigned char *edid, int size, struct edid *out)
"\tDetailed blocks filled with garbage\n");
if (!c.has_valid_dummy_block)
printk(BIOS_ERR, "\tDummy block filled with garbage\n");
if (!c.has_valid_extension_count)
printk(BIOS_ERR,
"\tImpossible extension block count\n");
if (!c.manufacturer_name_well_formed)
printk(BIOS_ERR,
"\tManufacturer name field contains garbage\n");