linux-kernel - [PATCH] dell-laptop: add parameter to disable the backlight device.

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Message-ID: <1386510031.81267.YahooMailNeo@web160401.mail.bf1.yahoo.com>
Date:	Sun, 8 Dec 2013 05:40:31 -0800 (PST)
From:	Alex Davis <alex14641@...oo.com>
To:	"mjg59@...f.ucam.org" <mjg59@...f.ucam.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject:  [PATCH] dell-laptop: add parameter to disable the backlight device.

I have a Dell Inspiron N7010 Laptop with Intel graphics. When the dell-laptop module is loaded,
two backlight device devices are created; dell_backlight, and intel_backlight from the Intel
graphics driver. The dell_backlight device is non-functional, but the graphics subsystem uses
it instead of the functioning intel_backlight device. The result is that, when running KDE,
screen brightness cannot be controlled. I've added a module parameter, disable_backlight
which, when true, will disable the dell_backlight device, and leave only the intel_backlight:
with this, screen brightness can be controlled.

This patch is against 3.10.

Signed-off-by: Alex Davis <alex14641@...oo.com>
--- dell-laptop.c.orig    2013-12-01 19:05:39.693149050 -0500
+++ dell-laptop.c    2013-12-01 17:29:27.613372482 -0500
@@ -35,6 +35,9 @@
 /* This structure will be modified by the firmware when we enter
  * system management mode, hence the volatiles */

+static bool disable_backlight;
+module_param(disable_backlight, bool, 0644);
+
 struct calling_interface_buffer {
     u16 class;
     u16 select;
@@ -561,6 +564,9 @@ static int __init dell_init(void)

     dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL);

+    if (disable_backlight)
+        return 0;
+
 #ifdef CONFIG_ACPI
     /* In the event of an ACPI backlight being available, don't
      * register the platform controller.

I code, therefore I am
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