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

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Message-ID: <1352062724.14888.206.camel@mfleming-mobl1.ger.corp.intel.com>
Date:	Sun, 04 Nov 2012 20:58:44 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Jonathan Nieder <jrnieder@...il.com>
Cc:	Corentin Chary <corentincj@...aif.net>,
	Matthew Garrett <mjg@...hat.com>, linux-kernel@...r.kernel.org,
	linux-efi@...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>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] samsung-laptop: Disable if CONFIG_EFI=y

On Sun, 2012-11-04 at 09:47 -0800, Jonathan Nieder wrote:
> Matt Fleming wrote:
> 
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -717,7 +717,7 @@ config XO15_EBOOK
> > 
> >  config SAMSUNG_LAPTOP
> >  	tristate "Samsung Laptop driver"
> > -	depends on X86
> > +	depends on X86 && !EFI
> 
> That means distros would just not get the samsung-laptop driver.
> Is there a runtime check that could be used instead?

Well, the closest thing we have at the moment is the 'efi_enabled'
variable, but that doesn't actually mean "We were booted from EFI?", it
means "Do we have EFI runtime services?", and that's not a broad enough
check for this case. We don't have access to the EFI runtime services
when a 64-bit kernel is booted from 32-bit EFI firmware or vice-versa.
Notably the chromebooks use this scheme. And seeing as Samsung make
chromebooks, I'm not convinced we won't hit that case.

But yeah, you've got a valid point. Clearly we need a way to check this
at runtime. I'll repsin this patch.

-- 
Matt Fleming, Intel Open Source Technology Center

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