On Thu, Jan 18, 2007 at 03:33:44PM +0530, Ashok kumar wrote: > On 1/17/07, Erik Mouw <mouw@xxxxxxxxxxxx> wrote: > >There is nothing wrong. Your machine probably traps access to the > >keyboard controller and uses SMM (system management mode) to emulate a > >real keyboard. > > i did not get it. can you please explain this?. > usb host controller driver itself is not loaded then how it can > contact through usb bus? Because the BIOS emulates it. It does that by trapping access to the keyboard controller registers, which cause the CPU to enter SMM. In SMM the BIOS handles the USB bus traffic from the keyboard, updates the CPU registers as if the CPU really read from the keyboard controller, exits SMM after which the CPU resumes normal operation (in the kernel keyboard driver). Note: this is not a normal BIOS call as you would use in DOS. This happens at a much lower level. SMM traps are completely transparent to the OS (though you can sometimes see lost interrupts). Erik -- They're all fools. Don't worry. Darwin may be slow, but he'll eventually get them. -- Matthew Lammers in alt.sysadmin.recovery
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