Re: [PATCH] Disable i8042 checks on Intel Apple Macs

From: H. Peter Anvin
Date: Fri Jan 22 2010 - 17:50:17 EST

On 01/22/2010 02:33 PM, Robert Hancock wrote:
>> You think it's reasonable to have the keyboard not work because
>> someone's KVM switch was in the wrong position when the system booted?
>> Sorry, that's not how the world works. It's sad that someone had the
>> bright idea that things should work that way, but that is definitely a
>> regression I wouldn't want to deal with.
> I don't imagine most KVM switches would result in this - they usually
> emulate the presence of a keyboard and mouse on all ports even if the
> input isn't the active one. It could be the reporter had an older
> switch that didn't do this.

The good ones do. The bad (cheap) ones just provide for a basic
electric disconnect. Heck, there used to be mechanical KVMs...

> I expect that it's quite common for the BIOS to disable the controller
> if no device is detected, though. I think the idea is to prevent a
> useless device from showing up in Device Manager and free up resources
> for other devices. Problem is if it does this, we don't really know
> what it did other than remove the PNP entry, and whether using the
> controller anyway will work safely.
> In any case, it's unlikely (though I admit I'm uncertain) that Windows
> is going to blindly probe for an 8042 controller if the PNP
> information doesn't indicate that one should be there - at least not
> if it's using the ACPI HAL. And for this sort of hardware
> compatibility issue, doing things differently than Windows does is
> ultimately asking for trouble in the long term. It's highly
> unreasonable to break that just for an unlikely corner case.

It's not unlikely - it's reality. Furthermore, BIOS programmers do
weird things all the time, especially to support, say, old Windows
versions that noone cares about anymore but mattered then.

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