From 0106406aff0f7aada992a9f27b68a20deafbc5e4 Mon Sep 17 00:00:00 2001
From: StapleButter <thetotalworm@gmail.com>
Date: Sat, 5 Aug 2017 19:13:55 +0200
Subject: [PATCH] * allow 128KB firmwares (DSi/3DS dumps) * document firmware
 sizes better

---
 README.md   |  7 ++++++-
 src/SPI.cpp | 40 ++++++++++++++++++++++++++++++++--------
 2 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index e80b0d77..550497c2 100644
--- a/README.md
+++ b/README.md
@@ -13,11 +13,16 @@ How to use:
 melonDS requires BIOS/firmware copies from a DS. Files required:
  * bios7.bin, 16KB: ARM7 BIOS
  * bios9.bin, 4KB: ARM9 BIOS
- * firmware.bin, 256KB: firmware
+ * firmware.bin, 128/256/512KB: firmware
  
 Firmware boot requires a firmware dump from an original DS or DS Lite.
 DS firmwares dumped from a DSi or 3DS aren't bootable and only contain configuration data, thus they are only suitable when booting games directly.
 
+Possible firmware sizes:
+ * 128KB: DSi/3DS DS-mode firmware (reduced size due to lacking bootcode)
+ * 256KB: regular DS firmware
+ * 512KB: iQue DS firmware
+
 DS BIOS dumps from a 3DS can be used with no compatibility issues. DSi BIOS dumps should be usable too, provided they were dumped properly.
 
 As for the rest, the interface should be pretty straightforward. If you have a question, don't hesitate to ask, though!
diff --git a/src/SPI.cpp b/src/SPI.cpp
index 9d00b58b..21f9ccb7 100644
--- a/src/SPI.cpp
+++ b/src/SPI.cpp
@@ -100,10 +100,23 @@ void Reset()
     fseek(f, 0, SEEK_END);
 
     FirmwareLength = (u32)ftell(f);
-    if (FirmwareLength != 0x40000 && FirmwareLength != 0x80000)
+    if (FirmwareLength != 0x20000 && FirmwareLength != 0x40000 && FirmwareLength != 0x80000)
     {
-        printf("Bad firmware size %d, assuming 256K\n", FirmwareLength);
-        FirmwareLength = 0x40000;
+        printf("Bad firmware size %d, ", FirmwareLength);
+
+        // pick the nearest power-of-two length
+        FirmwareLength |= (FirmwareLength >> 1);
+        FirmwareLength |= (FirmwareLength >> 2);
+        FirmwareLength |= (FirmwareLength >> 4);
+        FirmwareLength |= (FirmwareLength >> 8);
+        FirmwareLength |= (FirmwareLength >> 16);
+        FirmwareLength++;
+
+        // ensure it's a sane length
+        if (FirmwareLength > 0x80000) FirmwareLength = 0x80000;
+        else if (FirmwareLength < 0x20000) FirmwareLength = 0x20000;
+
+        printf("assuming %d\n", FirmwareLength);
     }
 
     Firmware = new u8[FirmwareLength];
@@ -352,7 +365,7 @@ u8 Read()
 }
 
 void Write(u8 val, u32 hold)
-{
+{printf("SPI powerman %02X %d\n", val, hold?1:0);
     if (!hold)
     {
         Hold = 0;
@@ -369,15 +382,26 @@ void Write(u8 val, u32 hold)
 
     if (DataPos == 1)
     {
+        u32 regid = Index & 0x07;
+
         if (Index & 0x80)
         {
-            Data = Registers[Index & 0x07];
+            Data = Registers[regid];
         }
         else
         {
-            Registers[Index & 0x07] =
-                (Registers[Index & 0x07] & ~RegMasks[Index & 0x07]) |
-                (val & RegMasks[Index & 0x07]);
+            Registers[regid] = (Registers[regid] & ~RegMasks[regid]) | (val & RegMasks[regid]);
+
+            switch (regid)
+            {
+            case 0:
+                if (val & 0x40) printf("DS shutdown\n");
+                printf("power %02X\n", val);
+                break;
+            case 4:
+                printf("brightness %02X\n", val);
+                break;
+            }
         }
     }
     else