From b895c7562197d90781ebccab0267c250398705fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Mon, 23 Aug 2021 17:34:55 +0200
Subject: [PATCH] main: add character in EDID product name to indicate firewall

---
 main.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/main.c b/main.c
index 8c0c7d8..9d815c7 100644
--- a/main.c
+++ b/main.c
@@ -170,6 +170,32 @@ static void load_edid(void)
 // save EDID + extension in EEPROM
 static bool save_edid(void)
 {
+	// modify EDID to include the character indicating the firewall
+	const char firewall_indicator = '|'; // sun character to indicate the firewall
+	// ensure descriptor 4 is for Display name
+	if ((0 == edid[108]) && (0 == edid[109]) && (0 == edid[110]) && (0xfc == edid[111]) && (0 == edid[112])) { // ensure descriptor 4 is for Display name
+		uint8_t last_c; // position of last character
+		for (last_c = 113; last_c < 126 && edid[last_c] != '\n'; last_c++); // find position for inserting our character
+		if (firewall_indicator != edid[last_c - 1]) { // the last character is not yet the sun
+			if (last_c > 125) { // ensure we insert as the last possible character
+				last_c = 125;
+			}
+			edid[last_c++] = firewall_indicator; // insert sun
+			if (last_c < 126) {
+				edid[last_c++] = '\n'; // insert LF to terminate string
+			}
+			while (last_c < 126) {
+				edid[last_c++] = ' '; // insert padding space
+			}
+			// calculate new checksum
+			uint8_t checksum = 0;
+			for (uint8_t i = 0; i < 127; i++) {
+				checksum += edid[i];
+			}
+			edid[127] = (256 - checksum);
+		}
+	}
+
 	return ram_eeprom_blockprog(edid, edid_length());
 }