%uA0
描述
This family of functions is used to do low level port input and output. The out* functions do port output, the in* functions do port input the b-suffix functions are byte-width and the w-suffix functions word-width the _p-suffix functions pause until the I/O completes.它们主要被设计为内部内核使用，但也可以从用户空间使用。
You compile with%uA0-O%uA0or%uA0-O2%uA0or similar. The functions are defined as inline macros, and will not be substituted in without optimization enabled, causing unresolved references at link time.
You use%uA0ioperm(2) or alternatively%uA0iopl(2) to tell the kernel to allow the user space application to access the I/O ports in question. Failure to do this will cause the application to receive a segmentation fault.
%uA0