linux-kernel - Re: your patch "x86, 8042: Enable A20 using KBC to fix S3 resume on some MSI laptops"

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Date:	Mon, 14 Jan 2013 08:37:59 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Ondrej Zary" <linux@...nbow-software.org>
Cc:	<dmitry.torokhov@...il.com>, <hpa@...ux.intel.com>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Rafael J. Wysocki" <rjw@...k.pl>, <linux-kernel@...r.kernel.org>
Subject: Re: your patch "x86, 8042: Enable A20 using KBC to fix S3
 resume on some MSI laptops"

>>> On 14.01.13 at 09:29, Ondrej Zary <linux@...nbow-software.org> wrote:
> On Monday 14 January 2013, Jan Beulich wrote:
>> Ondrej,
>>
>> I see two problems with this patch: For one, on a system without
>> i8042 the code at the place it got inserted ought to incur a stall of
>> 1s (50us * I8042_CTL_TIMEOUT [10000] * 2). I believe that this
>> code should not be run before i8042_controller_check() completed
>> successfully, but at the very least the second call to
>> i8042_command() should be conditional upon the first being
>> successful (effectively halving the stall).
> 
> I believe that all PnP-capable systems without 8042 will exit with -ENODEV 
> after x86_platform.i8042_detect().

How that, with default_i8042_detect() being just "return 1;"?

> Old non-PnP systems usually have 8042.

Sure.

>> Second, considering that enabling A20 (even if just in a fake way),
>> is a core system operation, I don't think it belongs into a driver
>> that is only optionally present in the kernel.
> 
> The first version of this patch added A20 enabling to early init code. But 
> that could be dangerous as it was run before any 8042 detection, possibly 
> breaking systems without 8042. I haven't found a better place for this.

I realize that the change would be more intrusive, but imo that's
not an excuse for not doing it properly.

Jan

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