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

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Date:	Thu, 21 Jan 2010 13:49:34 -0800
From:	"Justin P. Mattock" <justinmattock@...il.com>
To:	Robert Hancock <hancockrwd@...il.com>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	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 01/21/10 13:39, Robert Hancock wrote:
> 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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I've an iMac, and a macbook over here,
if you guys need me to test out a patch for this let me know.

Justin P. Mattock
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