linux-kernel - Re: [PATCH 0/3] Generic sysfs support for ACPI ALS and other ALS devices

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Message-ID: <20090805161931.GA9749@elf.ucw.cz>
Date:	Wed, 5 Aug 2009 18:19:31 +0200
From:	Pavel Machek <pavel@....cz>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	linux-acpi <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Matthew Garrett <mjg59@...f.ucam.org>, Greg KH <greg@...ah.com>
Subject: Re: [PATCH 0/3] Generic sysfs support for ACPI ALS and other ALS
	devices

On Wed 2009-08-05 09:02:50, Zhang Rui wrote:
> On Tue, 2009-08-04 at 21:21 +0800, Pavel Machek wrote:
> > On Mon 2009-08-03 17:10:57, Zhang Rui wrote:
> > > Hi, all,
> > > 
> > > This is the patch set I made to introduce ACPI ALS device driver
> > > and a generic sysfs I/F for all the ALS devices, like ACPI ALS,
> > > platform ALS, etc.
> > > 
> > > Patch 01 introduces the ACPI ALS device driver.
> > > 
> > > Patch 02 introduces ALS sysfs class.
> > > 	Two sysfs I/F are created for each ALS device.
> > >   /sys/class/als/alsX/illuminance:
> > > 	the amount of light incident upon a specified surface area.
> > >   /sys/class/als/alsX/mappings:
> > > 	ambient light illuminance to display luminance mappings
> > > 	that can be used by an OS to calibrate its ambient light policy
> > > 	this is what I got on a test box:
> > > 	cat /sys/class/als/als0/mappings
> > > 	???Illuminance	Adjustment
> > > 	          0	       70
> > > 	         10	       73
> > > 	         80	       85
> > > 	        300	      100
> > > 	       1000	      150
> > 
> > There's one value per file for sysfs... You should definitely have the
> > header. 
> > 
> > Is there chance to already return adjusted values, avoiding this
> > uglyness?
> 
> No,
> For a ALS policy, user space should set a brightness level as the base
> point, i.e. the backlight when display adjustment is 100.
> and then uses the adjustment values gotten from this mappings to
> calculate the actual brightness level the display should be put in.

Ok, so just make the code return only the "adjustement" -- userspace
does not really need to know "illuminance" and you can do the mapping
in the kernel AFAICT.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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