linux-kernel - RE: [PATCH] ACPI / button: Avoid using broken

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Date:	Tue, 22 Mar 2016 07:04:04 +0000
From:	"Zheng, Lv" <lv.zheng@...el.com>
To:	Bastien Nocera <hadess@...ess.net>,
	"Chen, Yu C" <yu.c.chen@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"cwhuang@...roid-x86.org" <cwhuang@...roid-x86.org>
Subject: RE: [PATCH] ACPI / button: Avoid using broken _LID on Surface tablet

Hi,

> From: Bastien Nocera [mailto:hadess@...ess.net]
> Subject: Re: [PATCH] ACPI / button: Avoid using broken _LID on Surface tablet
> 
> On Fri, 2016-03-04 at 03:37 +0000, Zheng, Lv wrote:
> <snip>
> >
> > > I'm not happy about the "fix" for this problem either, but blaming
> > > user-space for this is harsh, given the API exported by the kernel
> > > and
> > > how pretty much every laptop worked.
> > >
> > [Lv Zheng]
> > It worked for so many years on top of traditional x86 laptops where
> > the LID open event is handled by the BIOS to trigger a wake GPE.
> > Now we are talking about runtime idle systems where resuming from the
> > s2idle invokes no BIOS code.
> > The new case is still working on Windows.
> > Which forces us to re-consider the kernel API of the ACPI LID.
> 
> The current kernel API works on 99% of machines up until now, user-
> space could not have been expected to know that the Lid status might be
> incorrect on some machines, it had no way to know that, there was no
> documentation saying "don't use the Lid status outside of Lid status
> change events".
> 
> We either need to extend the current API to export the fact that we
> should ignore the LID status outside of events, or we need a new API.
> 
> (We could fix this without any kernel changes, but we really need the
> kernel to document that fact, and export it to user-space)
> 
> This is something you should have said at the start of the mail,
> instead of repeatedly saying that user-space was broken. User-space
> behaviour hasn't changed there for more than 10 years, and I'm fairly
> certain it's worked the same way as APM (on x86) and PMU (on Mac PPC
> machines) did.
[Lv Zheng] 
If you want a documentation fix.
It seems we need to fix ACPI spec first by clarifying this behavior.
By submitting ACPI spec change, we can also gain MS confirmation.
So please wait a bit longer to have this clarified.

Thanks
-Lv


> 
> Cheers