From 5d8ebf9200b2b8539cbb12639185304d9aae162e Mon Sep 17 00:00:00 2001
From: Mateusz Faderewski <sc@mateuszfaderewski.pl>
Date: Thu, 10 Aug 2023 22:39:26 +0200
Subject: [PATCH] Add PixelFX N64Digital/GEM support. (#28)

---
 Makefile        |  1 +
 src/hdmi/hdmi.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/hdmi/hdmi.h | 12 ++++++++++
 src/main.c      |  5 ++++
 4 files changed, 79 insertions(+)
 create mode 100644 src/hdmi/hdmi.c
 create mode 100644 src/hdmi/hdmi.h

diff --git a/Makefile b/Makefile
index a146ac81..dab647a1 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,7 @@ SRCS = \
 	flashcart/flashcart.c \
 	flashcart/sc64/sc64_ll.c \
 	flashcart/sc64/sc64.c \
+	hdmi/hdmi.c \
 	libs/libspng/spng/spng.c \
 	libs/mini.c/src/mini.c \
 	libs/miniz/miniz_tdef.c \
diff --git a/src/hdmi/hdmi.c b/src/hdmi/hdmi.c
new file mode 100644
index 00000000..aa6971c1
--- /dev/null
+++ b/src/hdmi/hdmi.c
@@ -0,0 +1,61 @@
+// Implementation based on https://gitlab.com/pixelfx-public/n64-game-id
+
+#include <libdragon.h>
+
+#include "hdmi.h"
+
+
+#define ROM_ADDRESS         (0x10000000)
+#define DDIPL_ADDRESS       (0x06000000)
+#define CONTROLLER_PORT     (0)
+#define GAME_ID_COMMAND     (0x1D)
+
+
+void hdmi_reset_game_id (void) {
+    uint8_t joybus_tx[10];
+    uint8_t joybus_rx[1];
+
+    memset(joybus_tx, 0, sizeof(joybus_tx));
+
+    execute_raw_command(
+        CONTROLLER_PORT,
+        GAME_ID_COMMAND,
+        sizeof(joybus_tx),
+        sizeof(joybus_rx),
+        joybus_tx,
+        joybus_rx
+    );
+}
+
+void hdmi_broadcast_game_id (boot_params_t *boot_params) {
+    uint8_t rom_header[0x40] __attribute__((aligned(8)));
+    uint32_t pi_address = ROM_ADDRESS;
+
+    if (boot_params->device_type == BOOT_DEVICE_TYPE_DD) {
+        pi_address = DDIPL_ADDRESS;
+    }
+
+    dma_read_async(rom_header, pi_address, sizeof(rom_header));
+    dma_wait();
+
+    uint8_t joybus_tx[10];
+    uint8_t joybus_rx[1];
+
+    // Copy CRC
+    memcpy(joybus_tx, rom_header + 0x10, 8);
+
+    // Copy media format
+    joybus_tx[8] = rom_header[0x3B];
+
+    // Copy country code
+    joybus_tx[9] = rom_header[0x3E];
+
+    execute_raw_command(
+        CONTROLLER_PORT,
+        GAME_ID_COMMAND,
+        sizeof(joybus_tx),
+        sizeof(joybus_rx),
+        joybus_tx,
+        joybus_rx
+    );
+}
diff --git a/src/hdmi/hdmi.h b/src/hdmi/hdmi.h
new file mode 100644
index 00000000..222974c8
--- /dev/null
+++ b/src/hdmi/hdmi.h
@@ -0,0 +1,12 @@
+#ifndef HDMI_H__
+#define HDMI_H__
+
+
+#include "boot/boot.h"
+
+
+void hdmi_reset_game_id (void);
+void hdmi_broadcast_game_id (boot_params_t *boot_params);
+
+
+#endif
diff --git a/src/main.c b/src/main.c
index d188c650..f8dde253 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,14 +1,19 @@
 #include <libdragon.h>
 
 #include "boot/boot.h"
+#include "hdmi/hdmi.h"
 #include "menu/menu.h"
 
 
 int main (void) {
     boot_params_t boot_params;
 
+    hdmi_reset_game_id();
+
     menu_run(&boot_params);
 
+    hdmi_broadcast_game_id(&boot_params);
+
     disable_interrupts();
 
     boot(&boot_params);