Subject: Re: [PATCH] [RESEND] Add Dell laptop backlight brightness display
From: Richard Purdie <rpurdie@rpsys.net>
To: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Dmitry Torokhov <dtor_core@ameritech.net>, linux-kernel@vger.kernel.org
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Date: Tue, 07 Feb 2006 13:06:45 +0000
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On Tue, 2006-02-07 at 12:32 +0000, Matthew Garrett wrote:
+       /* The backlight interface doesn't give us a means of providing
+          more than one brightness value, so we put the AC value in the
+          top bits of the brightness and the DC value in the bottom bits */

This is total abuse of the backlight class. The idea is that
cat /sys/class/backlight/ccc/brightness returns the *current* backlight
brightness. On AC power it should return the AC brightness value and on
DC power return the DC value.

If you want to know the DC and AC values as stored in the BIOS they
should be device specific attributes, not generic class ones.

I have a patch in the pipeline to change the backlight class slightly to
provide both the user requested brightness and the current brightness as
the two can differ (the Zaurus handhelds limit the backlight intensity
on low power).

Richard


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