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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Jan Engelhardt <jengelh@inai.de>
Cc:     linux-acpi@vger.kernel.org
Subject: Re: [PATCH] x86: ignore unspecified bit positions in the ACPI global lock field
Date:   Thu, 19 Mar 2020 13:22:18 +0100
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On Thursday, March 19, 2020 11:46:13 AM CET Jan Engelhardt wrote:
> 
> On Saturday 2020-03-14 10:46, Rafael J. Wysocki wrote:
> >On Thursday, March 5, 2020 1:24:25 PM CET Jan Engelhardt wrote:
> >> The value in "new" is constructed from "old" such that all bits defined
> >> as reserved by the ACPI spec[1] are left untouched. But if those bits
> >> do not happen to be all zero, "new < 3" will not evaluate to true.
> >> 
> >> The firmware of the laptop(s) Medion MD63490 / Akoya P15648 comes with
> >> garbage inside the "FACS" ACPI table. The starting value is
> >> old=0x4944454d, therefore new=0x4944454e, which is >= 3. Mask off
> >> the reserved bits.
> >> 
> >> -	return (new < 3) ? -1 : 0;
> >> +	return ((new & 0x3) < 3) ? -1 : 0;
> >
> >Applied as 5.7 material, thanks!
> 
> Would it make sense to funnel this into the upcoming 5.6?
> 

It's been marked for -stable, so it will get into 5.6.y early.

Hopefully, it will get some extra test coverage before that.