[coreboot] disabling bios usb stack

Scott Duplichan scott at notabs.org
Thu Aug 28 21:52:29 CEST 2014

ron minnich [mailto:rminnich at gmail.com] wrote:

]Thanks scott!
]So, what does an OS do to disable USB in the operating system? We have
]seen Linux do it, we're not quite sure just what
]place it gets done.

If I understand your question, I am not sure I know the answer. If you
boot linux with grub option 'nousb', or reboot Windows after disabling
usb controllers from device manager, what happens? I assume the operating
system just ignores USB controllers. It seems unlikely that the OS would
take some action to ensure that they are properly disabled. Does UEFI
disable USB controllers before handoff to the OS loader? I do not know.
Having the OS not load USB drivers should eliminate USB related interrupts,
but I know EHCI can generate memory accesses even when idle.


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