linux-kernel - Re: [PATCH] samsung-laptop: Disable if CONFIG

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Message-ID: <1352116219.14888.262.camel@mfleming-mobl1.ger.corp.intel.com>
Date:	Mon, 05 Nov 2012 11:50:19 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Corentin Chary <corentincj@...aif.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Matthew Garrett <mjg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-efi@...r.kernel.org,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	Alessandro Crismani <alessandro.crismani@...il.com>,
	Mikhail Bakhterev <mike.bakhterev@...il.com>,
	Patrick H <kernel@...storm.net>,
	"H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: Re: [PATCH] samsung-laptop: Disable if CONFIG_EFI=y

On Mon, 2012-11-05 at 11:30 +0100, Greg KH wrote:
> Odds are, the windows driver just isn't even loaded on the newer
> machines, as ACPI works just fine for this.  But, we don't have the
> option of shipping custom systems for different laptops like Samsung
> does, so we have to probe for this somehow.
> 
> Initally we were looking at the DMI strings for specific laptop models,
> but that got annoying as we had to keep adding new models.  So we now
> just check the memory locations for all Samsung laptops, which was
> working fine.
> 
> What is the problem if we try to access this memory on UEFI machines?
> What is the error that is caused?

Machine Check Exceptions are generated.

> Is there any "this_is_a_uefi_system()" type call drivers can make to
> just opt-out if that call is true?

There is the 'efi_enabled' variable, but it doesn't strictly mean
"this_is_a_uefi_system()", it actually means "Do we have EFI runtime
services?". The whole thing is a bit of a mess and I'm planning on
cleaning it up this week.

-- 
Matt Fleming, Intel Open Source Technology Center

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