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edid: allow arbitrary-length checksums

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Some of the EDID extensions like DisplayID do checksums of their
subsections. Currently checksums can be only applied to the whole
extension blocks which are 128 bytes.

This patch allows to checksum arbitrary parts of EDID, and not only
whole extension blocks.

Based-on: <20210303152948.59943-2-akihiko.odaki@gmail.com>
Signed-off-by: Konstantin Nazarov <mail@knazarov.com>
Message-Id: <20210315114639.91953-2-mail@knazarov.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20210427150824.638359-1-kraxel@redhat.com
Message-Id: <20210427150824.638359-8-kraxel@redhat.com>
This commit is contained in:
Konstantin Nazarov 2021-04-27 17:08:23 +02:00 committed by Gerd Hoffmann
parent 850dc61f5f
commit 5a4e88cf3b
1 changed files with 5 additions and 5 deletions
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10
hw/display/edid-generate.c
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@ -159,17 +159,17 @@ static void edid_fill_modes(uint8_t *edid, uint8_t *xtra3, uint8_t *dta,
}
}
static void edid_checksum(uint8_t *edid)
static void edid_checksum(uint8_t *edid, size_t len)
{
uint32_t sum = 0;
int i;
for (i = 0; i < 127; i++) {
for (i = 0; i < len; i++) {
sum += edid[i];
}
sum &= 0xff;
if (sum) {
edid[127] = 0x100 - sum;
edid[len] = 0x100 - sum;
}
}
@ -474,9 +474,9 @@ void qemu_edid_generate(uint8_t *edid, size_t size,
/* =============== finish up =============== */
edid_checksum(edid);
edid_checksum(edid, 127);
if (dta) {
edid_checksum(dta);
edid_checksum(dta, 127);
}
}