From: Danny Kukawka <dkukawka@suse.de>
Date: Tue, 3 Jul 2007 05:33:53 +0000 (-0400)
Subject: ACPI video: Don't export sysfs backlight interface if query _BCL fail
X-Git-Tag: v2.6.23-rc1~17^2~3^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f70ac0e9651aa8c07dffe72a44872f92054d42c3;p=pandora-kernel.git

ACPI video: Don't export sysfs backlight interface if query _BCL fail

Currently the acpi video module export the backlight interface to sysfs
also if acpi_video_device_lcd_query_levels() fails to read _BLC method
(e.g.  because the method is not available).  In this case the userspace
don't know which brightness level are supported and can't set a brightness
level (echo return with: "write error: Invalid Argument").  This happend
e.g.  on a ASUS RF1 (correct supported by the asus-laptop module).

The video module should not export the backlight interface if query _BLC fail,
because you can't set anything from userspace and this make it useless.

http://bugzilla.kernel.org/show_bug.cgi?id=8375

Signed-off-by: Danny Kukawka <dkukawka@suse.de>
Acked-by: Luming Yu <luming.yu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---

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