From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Danny Baumann <dannybaumann@web.de>
Cc: David Airlie <airlied@linux.ie>,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/1] drm/i915: Allow specifying a minimum brightness level for sysfs control.
Date: Tue, 26 Mar 2013 17:21:04 +0000 [thread overview]
Message-ID: <20130326172103.GA24566@srcf.ucam.org> (raw)
In-Reply-To: <5151D686.9070701@web.de>
On Tue, Mar 26, 2013 at 06:10:30PM +0100, Danny Baumann wrote:
> Am 26.03.2013 18:02, schrieb Matthew Garrett:
> >I'm not quite clear what you mean here. The behaviour of "0" isn't well
> >defined for the ACPI backlight driver - it's perfectly reasonable for it
> >to turn the backlight off entirely. Anything assuming that "0" is still
> >visible is broken.
>
> Well, the ACPI spec says this (section B.5.2):
>
> "
> The OEM may define the number 0 as "Zero brightness" that can mean
> to turn off the lighting (e.g. LCD panel backlight) in the device.
> This may be useful in the case of an output device that can still be
> viewed using only ambient light, for example, a transflective LCD.
> "
>
> My interpretation of this is that the value 0 is supposed to still
> be visible. I'm pretty sure I saw a statement that 0 is supposed to
> mean "barely visible" somewhere, but can't find it at the moment.
> I'll search for the source of it.
I think that's a stretch - "This may be useful" isn't normative
language, "The OEM may define" is. But even if we do assert it for the
ACPI backlight, it's not true for other interfaces - zero backlight
intensity is supposed to be screen off on Apple hardware, for instance.
--
Matthew Garrett | mjg59@srcf.ucam.org
next prev parent reply other threads:[~2013-03-26 17:21 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-26 11:48 [PATCH 0/1] drm/i915: Allow specifying a minimum brightness level for sysfs control Danny Baumann
2013-03-26 11:48 ` [PATCH 1/1] " Danny Baumann
2013-03-26 15:13 ` Daniel Vetter
2013-03-26 15:20 ` Chris Wilson
2013-03-26 17:04 ` Danny Baumann
2013-03-26 16:55 ` Danny Baumann
2013-03-26 17:02 ` [PATCH 0/1] " Matthew Garrett
2013-03-26 17:10 ` Danny Baumann
2013-03-26 17:21 ` Matthew Garrett [this message]
2013-03-27 11:56 ` Danny Baumann
2013-03-27 12:35 ` Alex Deucher
2013-03-27 12:56 ` Danny Baumann
2013-03-27 13:06 ` Alex Deucher
2013-03-27 15:10 ` Matthew Garrett
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