From 3e386c1792d893f5c75bc02b1e86fafc1b7b2383 Mon Sep 17 00:00:00 2001
From: Maximilian Stiefel <stiefel.maximilian@online.de>
Date: Wed, 24 Jun 2020 23:08:28 +0200
Subject: [PATCH] Display serial number descriptor and checksum implemented

---
 edid_stockach.json |  3 ++
 main.c             | 77 +++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 73 insertions(+), 7 deletions(-)

diff --git a/edid_stockach.json b/edid_stockach.json
index 22d755d..7155f0e 100644
--- a/edid_stockach.json
+++ b/edid_stockach.json
@@ -148,5 +148,8 @@
   },
   "display_name_descriptor": {
     "name": "24EN33"
+  },
+  "display_serial_number_descriptor": {
+    "serial_number": "303NDQAHV492"
   }
 }
diff --git a/main.c b/main.c
index 2782db3..171b0ce 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,8 @@
 #include <stdlib.h>
 #include "frozen/frozen.h"
 
-#define EDID_LENGTH 128
+#define EDID_LEN 128
+#define EDID_DISPLAY_DESCRIPTOR_DATA_LEN 13
 
 enum edid_analog_display_t {
   EDID_DISPLAY_TYPE_MONOCHROME_OR_GRAYSCALE = 0,
@@ -113,7 +114,7 @@ typedef struct __attribute__ (( packed )) {
   uint8_t reserved0;
   uint8_t descriptor_type;
   uint8_t reserved1;
-  uint8_t descriptor_data[13];
+  uint8_t descriptor_data[EDID_DISPLAY_DESCRIPTOR_DATA_LEN];
 } display_descriptor_t;
 
 typedef struct __attribute__ (( packed )) {
@@ -972,13 +973,13 @@ static int generate_display_name_descriptor(
                 "{display_name_descriptor: {name: %Q}}",
                 &display_name);
     if (display_name != NULL) {
-      if (strlen(display_name) <= 13) {
+      if (strlen(display_name) <= EDID_DISPLAY_DESCRIPTOR_DATA_LEN) {
         memcpy(edid->display_name_descriptor.descriptor_data, display_name, strlen(display_name));
-        if (strlen(display_name) < 13) {
+        if (strlen(display_name) < EDID_DISPLAY_DESCRIPTOR_DATA_LEN) {
           memset( edid->display_name_descriptor.descriptor_data
                   + strlen(display_name), 0x0A, 1);
           memset( edid->display_name_descriptor.descriptor_data
-                  + strlen(display_name) + 1, 0x20, 13-strlen(display_name)-1);
+                  + strlen(display_name) + 1, 0x20, EDID_DISPLAY_DESCRIPTOR_DATA_LEN-strlen(display_name)-1);
         }
       } else {
         printf("Error: Display name is too long.\n");
@@ -995,9 +996,69 @@ static int generate_display_name_descriptor(
   return 0;
 }
 
+static int generate_display_serial_number_descriptor(
+  edid_t* edid,
+  unsigned char* json_str,
+  size_t json_len)
+{
+  char* serial_number = NULL;
+
+  if (edid && json_str) {
+    edid->display_serial_number_descriptor.display_descriptor = 0;
+    edid->display_serial_number_descriptor.reserved0 = 0;
+    edid->display_serial_number_descriptor.descriptor_type = 0xFF;
+    edid->display_serial_number_descriptor.reserved1 = 0;
+    json_scanf( json_str, json_len,
+                "{display_serial_number_descriptor: {serial_number: %Q}}",
+                &serial_number);
+    if (serial_number != NULL) {
+      if (strlen(serial_number) <= EDID_DISPLAY_DESCRIPTOR_DATA_LEN) {
+        memcpy(edid->display_serial_number_descriptor.descriptor_data, serial_number, strlen(serial_number));
+        if (strlen(serial_number) < EDID_DISPLAY_DESCRIPTOR_DATA_LEN) {
+          memset( edid->display_serial_number_descriptor.descriptor_data
+                  + strlen(serial_number), 0x0A, 1);
+          memset( edid->display_serial_number_descriptor.descriptor_data
+                  + strlen(serial_number) + 1, 0x20, EDID_DISPLAY_DESCRIPTOR_DATA_LEN-strlen(serial_number)-1);
+        }
+      } else {
+        printf("Error: Display name is too long.\n");
+        return 1;
+      }
+    } else {
+      printf("Error: Could not parse JSON file somewhere around display_serial_number_descriptor.\n");
+      return 1;
+    }
+  } else {
+    printf("Error: One of either edid or json_str is NULL.\n");
+    return 1;
+  }
+  return 0;
+}
+
+static int generate_checksum(
+  edid_t* edid,
+  unsigned char* json_str,
+  size_t json_len)
+{
+  uint8_t* _edid = NULL;
+  unsigned int sum = 0;
+
+  if (edid && json_str) {
+    // Was ist denn mit Carsten los?
+    _edid = (uint8_t*)edid;
+    for (int sanny=0; sanny<EDID_LEN-1; sanny++) {
+      sum += _edid[sanny];
+    }
+    edid->checksum = 256-(sum % 256);
+  } else {
+    printf("Error: One of either edid or json_str is NULL.\n");
+    return 1;
+  }
+  return 0;
+}
+
 int main(void)
 {
-  //uint8_t edith[EDID_LENGTH];
   edid_t edith;
   memset(&edith, 0x00, sizeof(edith));
   printf("size> %d bytes\n", sizeof(edith));
@@ -1016,7 +1077,9 @@ int main(void)
   generate_detailed_timing_descriptor(&edith, mystr, len);
   generate_range_limit_descriptor(&edith, mystr, len);
   generate_display_name_descriptor(&edith, mystr, len);
-  disp_buf((uint8_t*)&edith, EDID_LENGTH);
+  generate_display_serial_number_descriptor(&edith, mystr, len);
+  generate_checksum(&edith, mystr, len);
+  disp_buf((uint8_t*)&edith, EDID_LEN);
   free(mystr);
   return 0;
 }