Initial commit

arm9/source/patches/platform/melonds/MelonDSLoaderPlatform.h

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+#pragma once
+#include "common.h"
+#include "../LoaderPlatform.h"
+#include "melondsReadSdAsm.h"
+#include "melondsWriteSdAsm.h"
+
+/// @brief Implementation of LoaderPlatform for MelonDS
+class MelonDSLoaderPlatform : public LoaderPlatform
+{
+public:
+    const SdReadPatchCode* CreateSdReadPatchCode(
+        PatchCodeCollection& patchCodeCollection, PatchHeap& patchHeap) const override
+    {
+        return patchCodeCollection.GetOrAddSharedPatchCode([&]
+        {
+            return new MelonDSReadSdPatchCode(patchHeap);
+        });
+    }
+
+    const SdWritePatchCode* CreateSdWritePatchCode(
+        PatchCodeCollection& patchCodeCollection, PatchHeap& patchHeap) const override
+    {
+        return patchCodeCollection.GetOrAddSharedPatchCode([&]
+        {
+            return new MelonDSWriteSdPatchCode(patchHeap);
+        });
+    }
+};

arm9/source/patches/platform/melonds/melondsReadSdAsm.h

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+#pragma once
+#include "sections.h"
+#include "../SdReadPatchCode.h"
+
+DEFINE_SECTION_SYMBOLS(melonds_readsd);
+
+extern "C" void melonds_readSd(u32 srcSector, void* dst, u32 sectorCount);
+
+class MelonDSReadSdPatchCode : public SdReadPatchCode
+{
+public:
+    explicit MelonDSReadSdPatchCode(PatchHeap& patchHeap)
+        : SdReadPatchCode(SECTION_START(melonds_readsd), SECTION_SIZE(melonds_readsd), patchHeap) { }
+
+    const SdReadFunc GetSdReadFunction() const override
+    {
+        return (const SdReadFunc)GetAddressAtTarget((void*)melonds_readSd);
+    }
+};

arm9/source/patches/platform/melonds/melondsReadSdAsm.s

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+.cpu arm7tdmi
+.section "melonds_readsd", "ax"
+.syntax unified
+.thumb
+
+// r0 = src sector
+// r1 = dst
+// r2 = sector count
+.global melonds_readSd
+.type melonds_readSd, %function
+melonds_readSd:
+    push {r4-r7,lr}
+
+    ldr r4, =0x040001A0
+    movs r3, #0x80
+    strb r3, [r4,#1]
+
+sector_loop:
+    // sd read for sector 0xaabbccdd
+    // C0 aa bb cc dd 00 00 00
+    movs r3, #0xC0
+    strb r3, [r4,#0x8]
+    lsrs r3, r0, #24
+    strb r3, [r4,#0x9]
+    lsrs r3, r0, #16
+    strb r3, [r4,#0xA]
+    lsrs r3, r0, #8
+    strb r3, [r4,#0xB]
+    lsls r7, r0, #24
+    lsrs r7, r7, #24 // r7 = dd
+    str r7, [r4,#0xC] // storing as little-endian puts the bottom 8 bits as first byte
+
+    ldr r6, =0x04100010
+    ldr r3, =0xA1586000
+    str r3, [r4,#4]
+
+C0_data_loop:
+    ldr r3, [r4, #4]
+    lsrs r3, r3, #24 // check if data is ready
+    bcc C0_data_loop_check_transfer_end // if not skip reading
+
+    ldr r3, [r6]
+    stmia r1!, {r3}
+
+C0_data_loop_check_transfer_end:
+    ldr r3, [r4, #4]
+    lsrs r3, r3, #32 // check if transfer is done
+    bcs C0_data_loop
+
+    adds r0, #1
+    subs r2, #1
+    bne sector_loop
+
+    pop {r4-r7,pc}
+
+.balign 4
+
+.pool
+
+.end

arm9/source/patches/platform/melonds/melondsWriteSdAsm.h

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+#pragma once
+#include "sections.h"
+#include "../SdWritePatchCode.h"
+
+DEFINE_SECTION_SYMBOLS(melonds_writesd);
+
+extern "C" void melonds_writeSd(u32 dstSector, const void* src, u32 sectorCount);
+
+class MelonDSWriteSdPatchCode : public SdWritePatchCode
+{
+public:
+    explicit MelonDSWriteSdPatchCode(PatchHeap& patchHeap)
+        : SdWritePatchCode(SECTION_START(melonds_writesd), SECTION_SIZE(melonds_writesd), patchHeap) { }
+
+    const SdWriteFunc GetSdWriteFunction() const override
+    {
+        return (const SdWriteFunc)GetAddressAtTarget((void*)melonds_writeSd);
+    }
+};

arm9/source/patches/platform/melonds/melondsWriteSdAsm.s

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+.cpu arm7tdmi
+.section "melonds_writesd", "ax"
+.syntax unified
+.thumb
+
+// r0 = dst sector
+// r1 = src
+// r2 = sector count
+.global melonds_writeSd
+.type melonds_writeSd, %function
+melonds_writeSd:
+    push {r4-r7,lr}
+
+    ldr r4, =0x040001A0
+    movs r3, #0x80
+    strb r3, [r4,#1]
+
+sector_loop:
+    // write at sd sector 0xaabbccdd
+    // C1 aa bb cc dd 00 00 00
+    movs r3, #0xC1
+    strb r3, [r4,#0x8]
+    lsrs r3, r0, #24
+    strb r3, [r4,#0x9]
+    lsrs r3, r0, #16
+    strb r3, [r4,#0xA]
+    lsrs r3, r0, #8
+    strb r3, [r4,#0xB]
+    lsls r7, r0, #24
+    lsrs r7, r7, #24 // r7 = dd
+    str r7, [r4,#0xC] // storing as little-endian puts the bottom 8 bits as first byte
+
+    ldr r6, =0x04100010
+    ldr r3, =0xE1586000
+    str r3, [r4,#4]
+
+C1_data_loop:
+    ldr r3, [r4, #4]
+    lsrs r3, r3, #24 // check if ready to write
+    bcc C1_data_loop_check_transfer_end // if not skip reading
+
+    ldmia r1!, {r3}
+    str r3, [r6]
+
+C1_data_loop_check_transfer_end:
+    ldr r3, [r4, #4]
+    lsrs r3, r3, #32 // check if transfer is done
+    bcs C1_data_loop
+
+    adds r0, #1
+    subs r2, #1
+    bne sector_loop
+
+    pop {r4-r7,pc}
+
+.balign 4
+
+.pool
+
+.end