PC 中 LPT I/O 地址映射
我听说 USB 到 LPT 适配器能够映射 PC 传统并行端口地址。这种映射的级别是什么？我的意思是 - 是否可以通过使用“in”或“out”x86 汇编指令（在 Windows 或 Linux 中）来访问适配器的引脚？如果没有，地址被映射意味着什么？这是什么仿真？ 谢谢。
马尔钦
I heard about USB to LPT adapters that are capable of mapping PC legacy parallel port address. What is the level of such mapping? I mean - is it possible to access the adpater's pins by using 'in' or 'out' x86 assembler instructions (in Windows or Linux)? If not, what does it mean that the addresses are mapped? What kind of emulation is this?
Thanks.
Marcin
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从传统 I/O 端口地址到 USB 设备的映射很可能是通过在内核模式操作系统代码中捕获端口访问来处理的。对于现在的几代系统来说，操作系统已经能够将自己强加在应用程序代码和硬件之间，即使看起来像对应用程序的原始硬件访问的东西也不一定如此。
实际上，当处理器遇到原始端口访问时，它不会被执行，而是会调用操作系统服务例程。
A mapping from legacy I/O port addresses to a USB device is most likely handled by trapping the port access in kernel mode operating system code. For several generations of systems now, the operating system has been able to impose itself between application code and the hardware in such a way that even things that look like raw hardware access to the application are not necessarily so.
Effectively, when the processor comes upon that raw port access, it isn't executed but an operating system service routine is called instead.