successfully call f_mkfs(). it's a start I guess.

src/DSi_NAND.cpp

@@ -52,7 +52,10 @@ bool Init(FILE* nandfile, u8* es_keyY)
     if (!nandfile)
         return false;
 
-    ff_disk_open(FF_ReadNAND, FF_WriteNAND);
+    fseek(nandfile, 0, SEEK_END);
+    u64 nandlen = ftell(nandfile);
+
+    ff_disk_open(FF_ReadNAND, FF_WriteNAND, (LBA_t)(nandlen>>9));
 
     FRESULT res;
     res = f_mount(&CurFS, "0:", 0);

src/FATStorage.cpp

@@ -15,3 +15,106 @@
     You should have received a copy of the GNU General Public License along
     with melonDS. If not, see http://www.gnu.org/licenses/.
 */
+
+#include "FATStorage.h"
+#include "Platform.h"
+
+
+FATStorage::FATStorage()
+{
+    printf("FATStorage begin\n");
+    bool res = Build(".", 0x40000000, "melonDLDI.bin");
+    printf("FATStorage result: %d\n", res);
+}
+
+FATStorage::~FATStorage()
+{
+    //
+}
+
+
+FILE* FATStorage::FF_File;
+u64 FATStorage::FF_FileSize;
+
+UINT FATStorage::FF_ReadStorage(BYTE* buf, LBA_t sector, UINT num)
+{
+    if (!FF_File) return 0;
+
+    u64 addr = sector * 0x200ULL;
+    u32 len = num * 0x200;
+
+    if ((addr+len) > FF_FileSize)
+    {
+        if (addr >= FF_FileSize) return 0;
+        len = FF_FileSize - addr;
+        num = len >> 9;
+    }
+
+    fseek(FF_File, addr, SEEK_SET);
+
+    u32 res = fread(buf, 0x200, num, FF_File);
+    if (res < num)
+    {
+        if (feof(FF_File))
+        {
+            memset(&buf[0x200*res], 0, 0x200*(num-res));
+            return num;
+        }
+    }
+
+    return res;
+}
+
+UINT FATStorage::FF_WriteStorage(BYTE* buf, LBA_t sector, UINT num)
+{
+    if (!FF_File) return 0;
+
+    u64 addr = sector * 0x200ULL;
+    u32 len = num * 0x200;
+
+    if ((addr+len) > FF_FileSize)
+    {
+        if (addr >= FF_FileSize) return 0;
+        len = FF_FileSize - addr;
+        num = len >> 9;
+    }
+
+    fseek(FF_File, addr, SEEK_SET);
+
+    u32 res = fwrite(buf, 0x200, num, FF_File);
+    return res;
+}
+
+
+bool FATStorage::Build(const char* sourcedir, u64 size, const char* filename)
+{
+    filesize = size;
+
+    FF_File = Platform::OpenLocalFile(filename, "wb");
+    if (!FF_File)
+        return false;
+
+    FF_FileSize = size;
+    ff_disk_open(FF_ReadStorage, FF_WriteStorage, (LBA_t)(size>>9));
+
+    FRESULT res;
+
+    MKFS_PARM fsopt;
+    fsopt.fmt = FM_FAT | FM_FAT32;
+    fsopt.au_size = 0;
+    fsopt.align = 1;
+    fsopt.n_fat = 1;
+    fsopt.n_root = 512;
+
+    BYTE workbuf[FF_MAX_SS];
+    res = f_mkfs("0:", &fsopt, workbuf, sizeof(workbuf));
+    printf("MKFS RES %d\n", res);
+
+    //
+
+    ff_disk_close();
+    fclose(FF_File);
+    FF_File = nullptr;
+
+    return true;
+}

src/FATStorage.h

@@ -19,8 +19,28 @@
 #ifndef FATSTORAGE_H
 #define FATSTORAGE_H
 
-#include "types.h"
+#include <stdio.h>
 
-//
+#include "types.h"
+#include "fatfs/ff.h"
+
+
+class FATStorage
+{
+public:
+    FATStorage();
+    ~FATStorage();
+
+private:
+    FILE* file;
+    u64 filesize;
+
+    static FILE* FF_File;
+    static u64 FF_FileSize;
+    static UINT FF_ReadStorage(BYTE* buf, LBA_t sector, UINT num);
+    static UINT FF_WriteStorage(BYTE* buf, LBA_t sector, UINT num);
+
+    bool Build(const char* sourcedir, u64 size, const char* filename);
+};
 
 #endif // FATSTORAGE_H

src/NDSCart.cpp

@@ -1164,10 +1164,12 @@ u8 CartRetailBT::SPIWrite(u8 val, u32 pos, bool last)
 
 CartHomebrew::CartHomebrew(u8* rom, u32 len, u32 chipid) : CartCommon(rom, len, chipid)
 {
+    test = nullptr;
     if (Config::DLDIEnable)
     {
         ApplyDLDIPatch(melonDLDI, sizeof(melonDLDI));
         SDFile = Platform::OpenLocalFile(Config::DLDISDPath, "r+b");
+        test = new FATStorage();
     }
     else
         SDFile = nullptr;
@@ -1176,6 +1178,7 @@ CartHomebrew::CartHomebrew(u8* rom, u32 len, u32 chipid) : CartCommon(rom, len,
 CartHomebrew::~CartHomebrew()
 {
     if (SDFile) fclose(SDFile);
+    if (test) delete test;
 }
 
 void CartHomebrew::Reset()

src/NDSCart.h

@@ -21,6 +21,7 @@
 
 #include "types.h"
 #include "NDS_Header.h"
+#include "FATStorage.h"
 
 namespace NDSCart
 {
@@ -182,6 +183,7 @@ private:
     void ReadROM_B7(u32 addr, u32 len, u8* data, u32 offset);
 
     FILE* SDFile;
+    FATStorage* test;
 };
 
 extern u16 SPICnt;

src/fatfs/diskio.c

@@ -13,15 +13,17 @@
 
 static ff_disk_read_cb ReadCb;
 static ff_disk_write_cb WriteCb;
+static LBA_t SectorCount;
 static DSTATUS Status = STA_NOINIT | STA_NODISK;
 
 
-void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb)
+void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt)
 {
     if (!readcb) return;
 
     ReadCb = readcb;
     WriteCb = writecb;
+    SectorCount = seccnt;
 
     Status &= ~STA_NODISK;
     if (!writecb) Status |= STA_PROTECT;
@@ -32,6 +34,7 @@ void ff_disk_close()
 {
     ReadCb = (void*)0;
     WriteCb = (void*)0;
+    SectorCount = 0;
 
     Status &= ~STA_PROTECT;
     Status |= STA_NODISK;
@@ -123,12 +126,28 @@ DRESULT disk_ioctl (
 {
     switch (cmd)
     {
-    case 0: // sync
+    case CTRL_SYNC:
         // TODO: fflush?
         return RES_OK;
+
+    case GET_SECTOR_COUNT:
+        *(LBA_t*)buff = SectorCount;
+        return RES_OK;
+
+    case GET_SECTOR_SIZE:
+        *(WORD*)buff = 0x200;
+        return RES_OK;
+
+    case GET_BLOCK_SIZE:
+        *(DWORD*)buff = 1;
+        return RES_OK;
+
+    case CTRL_TRIM:
+        // TODO??
+        return RES_OK;
     }
 
-	//printf("disk_ioctl(%02X, %02X, %p)\n", pdrv, cmd, buff);
+	printf("FatFS: unknown disk_ioctl(%02X, %02X, %p)\n", pdrv, cmd, buff);
 	return RES_PARERR;
 }
 

src/fatfs/ff.h

@@ -420,7 +420,7 @@ int ff_del_syncobj (FF_SYNC_t sobj);	/* Delete a sync object */
 typedef UINT (*ff_disk_read_cb)(BYTE* buff, LBA_t sector, UINT count);
 typedef UINT (*ff_disk_write_cb)(BYTE* buff, LBA_t sector, UINT count);
 
-void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb);
+void ff_disk_open(ff_disk_read_cb readcb, ff_disk_write_cb writecb, LBA_t seccnt);
 void ff_disk_close();