From: Seth Forshee <seth.forshee@canonical.com>
To: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Len Brown <lenb@kernel.org>, "Rafael J. Wysocki" <rjw@sisk.pl>,
linux-acpi@vger.kernel.org, Ben Jencks <ben@bjencks.net>,
joeyli <jlee@suse.com>
Subject: Re: [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads
Date: Mon, 11 Feb 2013 13:06:17 -0600 [thread overview]
Message-ID: <20130211190617.GH13768@thinkpad-t410> (raw)
In-Reply-To: <20130211175213.GA25139@srcf.ucam.org>
On Mon, Feb 11, 2013 at 05:52:13PM +0000, Matthew Garrett wrote:
> On Mon, Feb 11, 2013 at 10:21:21AM -0600, Seth Forshee wrote:
> > The AML implementation for brightness control on several ThinkPads
> > contains a workaround to meet a Windows 8 requirement of 101 brightness
> > levels [1]. The implementation is flawed, as only 16 of the brighness
> > values reported by _BCL affect a change in brightness. _BCM silently
> > discards the rest of the values. Disabling Windows 8 compatibility on
> > these machines reverts them to the old behavior, making _BCL only report
> > the 16 brightness levels which actually work. Add a quirk to do this
> > along with a dmi callback to disable Win8 compatibility.
>
> So the problem is that userspace is writing values that don't happen to
> be aligned with the values the hardware reacts to, and so nothing gets
> changed?
Yes. The values are valid according to to _BCL, but _BCM is discarding
any values that aren't contained in an array named BRTW. BRTW is
literally the object returned by _BCL returns for !Windows 2012. Here's
a link to the AML if you'd like to take a look.
http://people.canonical.com/~sforshee/x230-acpi-tables/SSDT1.dsl
Seth
next prev parent reply other threads:[~2013-02-11 19:06 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-11 16:21 [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads Seth Forshee
2013-02-11 17:52 ` Matthew Garrett
2013-02-11 19:06 ` Seth Forshee [this message]
2013-02-11 19:09 ` Matthew Garrett
2013-02-11 19:31 ` Rafael J. Wysocki
2013-02-12 3:05 ` Seth Forshee
2013-02-13 20:32 ` Seth Forshee
2013-02-13 20:55 ` Matthew Garrett
2013-02-13 21:04 ` Ben Jencks
2013-02-13 21:49 ` Seth Forshee
2013-02-13 21:46 ` Seth Forshee
2013-02-13 21:54 ` Matthew Garrett
2013-02-13 22:04 ` Seth Forshee
2013-03-07 19:38 ` Seth Forshee
2013-03-07 19:39 ` [PATCH 1/5] ACPICA: Add interface for getting latest Windows version requested via _OSI Seth Forshee
2013-03-07 19:39 ` [PATCH 2/5] acpi_video: Avoid unnecessary conversions between backlight levels and indexes Seth Forshee
2013-03-07 19:39 ` [PATCH 3/5] acpi_video: Add workaround for broken Windows 8 backlight implementations Seth Forshee
2013-04-04 11:44 ` Aaron Lu
2013-04-04 12:35 ` Seth Forshee
2013-04-04 13:46 ` Aaron Lu
2013-04-04 14:02 ` Seth Forshee
2013-04-04 14:27 ` Aaron Lu
2013-03-07 19:39 ` [PATCH 4/5] acpi_video: Disable use of _BQC when value doesn't match those set through _BCM Seth Forshee
2013-03-07 19:39 ` [PATCH 5/5] acpi_video: Don't handle ACPI brightness notifications by default Seth Forshee
2013-08-02 5:55 ` Aaron Lu
2013-08-02 14:41 ` Rafael J. Wysocki
2013-08-02 14:52 ` Aaron Lu
2013-08-03 0:26 ` Rafael J. Wysocki
2013-08-03 9:46 ` Aaron Lu
2013-08-03 11:23 ` Rafael J. Wysocki
2013-08-03 12:10 ` Aaron Lu
2013-08-03 22:07 ` Rafael J. Wysocki
2013-08-04 1:08 ` Aaron Lu
2013-03-18 21:25 ` [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads Seth Forshee
2013-04-02 5:18 ` Ben Jencks
2013-04-02 9:15 ` Aaron Lu
2013-04-02 11:23 ` Matthew Garrett
2013-04-02 13:44 ` Aaron Lu
2013-04-02 19:08 ` Matthew Garrett
2013-04-19 12:24 ` Seth Forshee
2013-04-20 22:06 ` Rafael J. Wysocki
2013-04-21 2:29 ` Seth Forshee
2013-04-21 15:46 ` Henrique de Moraes Holschuh
2013-02-13 21:09 ` Ben Jencks
2013-04-01 1:53 ` Aaron Lu
2013-04-01 13:03 ` Seth Forshee
2013-04-02 9:08 ` Aaron Lu
2013-04-02 13:00 ` Seth Forshee
2013-04-02 13:43 ` Aaron Lu
2013-04-03 7:04 ` Ben Jencks
2013-04-03 7:27 ` Aaron Lu
2013-04-03 13:45 ` Seth Forshee
2013-04-04 11:39 ` Aaron Lu
2013-04-19 3:15 ` Aaron Lu
2013-04-20 22:06 ` Rafael J. Wysocki
2013-04-21 11:07 ` Aaron Lu
2013-04-21 12:11 ` Aaron Lu
2013-04-21 21:42 ` Rafael J. Wysocki
2013-04-22 9:39 ` Aaron Lu
2013-04-22 11:51 ` Rafael J. Wysocki
2013-04-22 12:11 ` Aaron Lu
2013-04-22 13:06 ` Seth Forshee
2013-04-22 13:40 ` Aaron Lu
2013-04-22 13:56 ` Seth Forshee
2013-04-22 14:07 ` Aaron Lu
2013-04-22 15:11 ` Seth Forshee
2013-04-22 2:18 ` joeyli
2013-04-22 10:08 ` Aaron Lu
2013-04-22 12:00 ` joeyli
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130211190617.GH13768@thinkpad-t410 \
--to=seth.forshee@canonical.com \
--cc=ben@bjencks.net \
--cc=jlee@suse.com \
--cc=lenb@kernel.org \
--cc=linux-acpi@vger.kernel.org \
--cc=mjg59@srcf.ucam.org \
--cc=rjw@sisk.pl \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).