Int 21 Fn 4404  - DOS 2+ - Ioctl - Read From Block Device Control Channel  [D]

   AX = 4404h
   BL = drive number (00h = default, 01h = A:, etc.)
   CX = number of bytes to read
   DS:DX -> buffer

Return: CF clear if successful
       AX = number of bytes actually read
   CF set on error
       AX = error code (01h,05h,06h,0Dh) (see AH=59h)

Note:  format of data is driver-specific

See Also: AX=4402h,AX=4405h,INT 2F/AX=122Bh