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

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Date:	Wed, 20 Jan 2010 18:41:56 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	Bastien Nocera <hadess@...ess.net>
CC:	linux-kernel <linux-kernel@...r.kernel.org>, pjones@...hat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs

On 01/20/2010 12:23 PM, Bastien Nocera wrote:
> As those computers never had any i8042 controllers, and the
> current lookup code could potentially lock up/hang/wait for
> timeout for long periods of time.
>
> Fixes intermittent hangs on boot on a MacbookAir1,1
>
> Signed-off-by: Bastien Nocera<hadess@...ess.net>

I assume this is happening because of this code in 
drivers/input/serio/i8042-x86ia64io.h:

         if (!i8042_pnp_kbd_devices && !i8042_pnp_aux_devices) {
                 i8042_pnp_exit();
#if defined(__ia64__)
                 return -ENODEV;
#else
                 printk(KERN_INFO "PNP: No PS/2 controller found. 
Probing ports directly.\n");
                 return 0;
#endif

In other words, on x86, if PNP and/or ACPI don't indicate any PS/2 
controller exists, we randomly bang on the ports in the expectation 
they'll be there anyway. This seems rather misguided. It would seem like 
a better idea to fix this rather than adding yet another DMI list 
(especially since there likely are, or will be, machines without i8042 
other than Macs).

I can see continuing on and probing if PNP isn't present on the machine, 
but certainly if ACPI is enabled, I don't think we should be doing such 
things.
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