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

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Message-ID: <1264037485.1735.4988.camel@localhost.localdomain>
Date:	Thu, 21 Jan 2010 01:31:25 +0000
From:	Bastien Nocera <hadess@...ess.net>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>, pjones@...hat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs

On Wed, 2010-01-20 at 18:41 -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

Actually, the error message is "i8042.c: No controller found". Which
happens very early in a sub-function of i8042_init().

So I don't think this would solve the problem.

> 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).

They might also have a better BIOS than the Macs and avoid hanging when
that happens...

> 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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