DeviceIOPorts
DeviceIOPorts are the set of hardware registers exposed by devices through a dedicated input/output address space, used for control, status, and data transfer. In x86 and some other architectures, this I/O space is separate from system memory and is accessed with dedicated instructions, such as IN and OUT, or via compiler intrinsics provided by the operating system. Each port is identified by a 16-bit address, allowing up to 65,536 distinct I/O locations. Devices may expose individual 8-bit registers or contiguous ranges, and software must rely on device documentation to interpret the meaning of each port.
Typical usage involves various legacy and some modern hardware components. For example, keyboard controllers commonly use
Access to DeviceIOPorts is tightly controlled. Direct I/O port access generally requires elevated privileges: in Linux,
In modern systems, I/O port usage has declined in favor of memory-mapped I/O and PCI/PCIe-based mechanisms, but