File content as of revision 0:0ab65a1aef12:

#include "mbed.h"
#include "FATFileSystem.h"
#include "Utils.h"

int MassStorage_ReadCapacity(int device, u32* blockCount, u32* blockSize);
int MassStorage_Read(int device, u32 blockAddr, u32 blockCount, u8* dst, u32 blockSize);
int MassStorage_Write(int device, u32 blockAddr, u32 blockCount, u8* dst, u32 blockSize);

class USBFileSystem : public FATFileSystem
{
    int _device;
    u32 _blockSize;
    u32 _blockCount;
    
public:
    USBFileSystem() : FATFileSystem("usb"),_device(0),_blockSize(0),_blockCount(0)
    {
    }
    
    void SetDevice(int device)
    {
        _device = device;
    }
    
    virtual int disk_initialize()
    {
        return MassStorage_ReadCapacity(_device,&_blockCount,&_blockSize);
    }
    
    virtual int disk_write(const char *buffer, int block_number)
    {
        return MassStorage_Write(_device,block_number,1,(u8*)buffer,_blockSize);
    }
    
    virtual int disk_read(char *buffer, int block_number)
    {
        return MassStorage_Read(_device,block_number,1,(u8*)buffer,_blockSize);
    }
        
    virtual int disk_sectors()
    {
        return _blockCount;
    }
};

void DumpFS(int depth, int count)
{
    DIR *d = opendir("/usb");
    if (!d)
    {
        printf("USB file system borked\n");
        return;
    }

    printf("\nDumping root dir\n");
    struct dirent *p;
    for(;;)
    {
        p = readdir(d);
        if (!p)
            break;
        int len = sizeof( dirent);
        printf("%s %d\n", p->d_name, len);
    }
    closedir(d);
}

int OnDiskInsert(int device)
{
    USBFileSystem fs;
    fs.SetDevice(device);
    DumpFS(0,0);
    return 0;
}