| 摘要 |
A method and system for controlling the addition of a USB device to a host computer system via a hardware hot plug detector that monitors USB ports. The differential signal lines connecting to the USB device are logically OR'ed together, such that logically high D+ or D- signals from the USB device signal a central processing unit's (CPU) system management interrupt (SMI) line to initiate system management mode (SMM). Entering SMM transfers control of the host computer system to an SMI Interrupt Handler BIOS, which resides in the SMM address space of the hose computer system. The SMM BIOS is loaded into the SMM address space during Power On Self Test (POST) and is secured prior to booting the Operating System (OS). The SMM BIOS code contains instructions as to whether or not the connected USB device should be made visible to the operating system of the computer. If the device is not authorized, it is disabled, the D+/D- lines are not connected to the USB host controller, and the SMI signal is cleared, allowing the computer to continue operation without the operating system ever being aware of the USB device.
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