readsects
if (size != 0 && readsects(0x40, sector + dblk, buf,
int readsects(int dev, uint32_t lba, void *buf, size_t size);
if (size != 0 && readsects(0x40, bios_sector + dblk, buf,
int readsects(int dev, uint32_t lba, void *buf, size_t size);