From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Contreras Subject: Re: [PATCH] acpi: video: improve quirk check Date: Sun, 4 Aug 2013 09:19:56 -0500 Message-ID: References: <1375472229-1563-1-git-send-email-felipe.contreras@gmail.com> <51FDABFD.3070601@gmail.com> <1861338.WxIinvfTH6@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-la0-f52.google.com ([209.85.215.52]:42013 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752774Ab3HDOT6 (ORCPT ); Sun, 4 Aug 2013 10:19:58 -0400 In-Reply-To: <1861338.WxIinvfTH6@vostro.rjw.lan> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: Aaron Lu , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Len Brown , Zhang Rui On Sun, Aug 4, 2013 at 9:19 AM, Rafael J. Wysocki wrote: > On Sunday, August 04, 2013 01:42:49 AM Felipe Contreras wrote: >> Personally I think there are better ways to fix the code for the >> synthetic case than what you patch does, which will also make _BQC >> work. That can be discussed later though, the one-liner is simple, and >> it works. > > So, let's assume that the one-liner goes into 3.11 and work further with that > assumption. > > How would you address the sythetic case (on top of the one-liner)? I would write and read two values instead of one. The code is trying to check if _BQC is always returning the maximum, and if you try with two values you can be absolutely certain if that's happening or not; it doesn't even matter which values you choose. Even in the synthetic case that only has two values the check would work correctly and detect that _BQC works correctly (or not). In my machine I think the issue is slightly different, I think _BCM is failing, at least until enabling the _DOS thing, but at the end of the day it's the same thing for the check; _BQC is always returning the same value, and the code above will find that out, regardless of which values are tested. For my particular machine though, I think it's more interesting to find out why _BCM is failing before _DOS, and why efaa14c made it work. If that is actually the case. -- Felipe Contreras