On Saturday 25 October 2008 04:09:45 am Jeremy Chadwick wrote: > Just for posterity: the USB Legacy Support BIOS option does not affect > natively-connected PS/2 keyboards; you can leave the option enabled even > in the scenario where you have a USB keyboard *and* a PS/2 keyboard > plugged in; one will not "trump" the other. Instead, you should have > two keyboards which function in OSes/environments which lack a USB > stack. (That is, until something resets/reassigns the BIOS-controlled > interrupt, which will then break USB->PS/2 emulation; the native PS/2 > keyboard should not be affected by this)
This last statement is not quite true (at least not always true). For many systems, the way the PS/2 emulation works is that accesses to the backing I/O ports (0x60 and 0x64) case a trap into SMM and the SMI handler in the BIOS then talks to the USB controller and keyboard and updates the register values to simulate the I/O port accesses. This is disabled by having the USB host controller driver frob flags in controller registers to disable the SMI traps. -- John Baldwin _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
