open($fd, "+<:unix", $dev_path) || die "Failed to open $dev_path : $!";

@regs = ($addr, 0x10111213, 0xaaaa, 0xbbbb);
$regs = pack('QQQ', @regs);
$rc = ioctl($fd, $REG_R, $regs);
($offset, $data0, $data1, $data2) = unpack('QQQ', $regs);