section .bss

		; drive actually selected for I/O
dsknum:		resb 1
		; current sector number
dskseek:	resd 1

		; disk buffer for I/O operations
dskbuf:		resb 512

dpt:		resb DPTSIZE

section .text

ret:		ret

		; Convert drive number into DL for int 13h
		; IN	dl	dos drive number
		; OUT	dl	bios drive number
getdl:		cmp dl, 2
		jc ret
		mov dl, 0x80
		ret

		; select drive
		; IN	dl	drive number
dsksel:		cmp dl, byte [dsknum]
		je ret

		call dskrst

		call getdl
		mov ah, 8
		les di, [0x1E*4]
		int 0x13

		; copy dpt
		mov bx, di
		mov dx, dpt
		mov cx, DPTSIZE
		call lod

		ret

dskrst:		call flush
		mov ax, 0xFFFF
		mov [dsknum], al
		mov [dskseek], ax
		mov [dskseek+2], ax
		ret

		; flush buffer if dirty
flush:		ret