linux-kernel - RE: [PATCH][v3] ACPI: Do not report _OSI("Darwin") when acpi

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Date:	Mon, 22 Feb 2016 08:55:56 +0000
From:	"Zheng, Lv" <lv.zheng@...el.com>
To:	"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>,
	"matthew.garrett@...ula.com" <matthew.garrett@...ula.com>,
	"andy.shevchenko@...il.com" <andy.shevchenko@...il.com>
Subject: RE: [PATCH][v3] ACPI: Do not report _OSI("Darwin") when
 acpi_osi=!Darwin provided

Hi,

> From: Chen, Yu C
> Subject: RE: [PATCH][v3] ACPI: Do not report _OSI("Darwin") when
> acpi_osi=!Darwin provided
> 
> 
> > From: Zheng, Lv
> > Subject: RE: [PATCH][v3] ACPI: Do not report _OSI("Darwin") when
> > acpi_osi=!Darwin provided
> >
> > Hi, Yu
> >
> > > From: linux-acpi-owner@...r.kernel.org [mailto:linux-acpi-
> > > owner@...r.kernel.org] On Behalf Of Chen Yu
> > > Subject: [PATCH][v3] ACPI: Do not report _OSI("Darwin") when
> > > acpi_osi=!Darwin provided
> > >
> > > Commit 7bc5a2bad0b8 ("ACPI: Support _OSI("Darwin") correctly") always
> > > reports positive value when Apple hardware queries _OSI("Darwin").
> > > But sometimes the users might want to tell the hardware they don't
> > > need the Darwin feature, for example, users may leverage the hardware
> > > to power off the Thunderbolt, by appending acpi_osi=!Darwin in command
> > > line, thus Apple hardware regards it as an incompatible OS X system,
> > > hence turns off the Thunderbolt.
> > [Lv Zheng]
> > Both this patch and the original commit that is from Matthew look wrong to
> > me.
> > IMO, the feature should be done with an entirely different approach.
> > Without test, I'm not sure if my comment is helpful for you.
> > So could you let me take over to fix this issue?
> >
> Yes, sure, thanks.
[Lv Zheng] 
It looks to me, the original Matthew's commit was trying to make the world easier with "acpi_osi=! acpi_osi=Darwin".
While it finally adds limitation to the acpi_osi= quirk mechanism and is proven to be a bad idea.
So why don't we just revert that commit?

According to my understanding, there is no better choice other than letting users to choose a non-recent-Windows OS that the kernel should pretend to be.
So that kernel can stay simple to just pretend to be "recent-Windows".

And the only improvement that is acceptable in this case is:
We can allow acpi_osi=Darwin to be equivalent to "acpi_osi=! acpi_osi=Darwin".
While I don't think this improvement is necessary.
All reporters, including the contribution vendors should have already been familiar with "acpi_osi=! acpi_osi=Darwin".

Thanks and best regards
-Lv

> 
> yu
>