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

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Date:	Thu, 21 Jan 2010 15:39:25 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Bastien Nocera <hadess@...ess.net>,
	linux-kernel <linux-kernel@...r.kernel.org>, pjones@...hat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs

On Thu, Jan 21, 2010 at 12:55 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Wed, Jan 20, 2010 at 06:41:56PM -0600, Robert Hancock wrote:
>> 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.
>
> Basically, we do not trust BIOS writers on x86 ;) In the past there were
> occasions when they forgot to mention presence of KBD/AUX in DSDT and
> elsewhere which lead to non-functional keyboard/mouse.

Are we certain about that? Any pointers to reports?

>
>> 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).
>>
>
> If they are not Macs that mean they are tested with windows and thus
> expect probes in i8042 port region so no harm done. In a few years if
> everyone uses USB only we could add a year threshold to trust ACPI/PNP
> data.

Macs will be tested with Windows too, so obviously it manages to avoid
this problem somehow, and I very much doubt it has an Apple-specific
check..
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