[PATCH v3 2/3] edid: allow arbitrary-length checksums

[Konstantin Nazarov <mail@knazarov.com>]

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>
---
 hw/display/edid-generate.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/display/edid-generate.c b/hw/display/edid-generate.c
index 1e1d89b9a78..530bdbdf06e 100644
--- a/hw/display/edid-generate.c
+++ b/hw/display/edid-generate.c
@@ -158,17 +158,17 @@ 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;
     }
 }
 
@@ -452,9 +452,9 @@ void qemu_edid_generate(uint8_t *edid, size_t size,
     /* =============== finish up =============== */
 
     edid_fill_modes(edid, xtra3, dta, info->maxx, info->maxy);
-    edid_checksum(edid);
+    edid_checksum(edid, 127);
     if (dta) {
-        edid_checksum(dta);
+        edid_checksum(dta, 127);
     }
 }
 
-- 
2.24.3 (Apple Git-128)