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

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Message-ID: <20100121185544.GB11996@core.coreip.homeip.net>
Date:	Thu, 21 Jan 2010 10:55:44 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Robert Hancock <hancockrwd@...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 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. 

> 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.

-- 
Dmitry
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