From mboxrd@z Thu Jan  1 00:00:00 1970
From: Darren Hart <dvhart@infradead.org>
Subject: Re: [PATCH v2] platform/x86: asus-wmi: Add keyboard backlight toggle
 support
Date: Mon, 4 Jun 2018 18:59:00 -0700
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To: Benjamin Berg <benjamin@sipsolutions.net>
Cc: Chris Chiu <chiu@endlessm.com>, Daniel Drake <drake@endlessm.com>, Hans de Goede <hdegoede@redhat.com>, Andy Shevchenko <andy.shevchenko@gmail.com>, Corentin Chary <corentin.chary@gmail.com>, Andy Shevchenko <andy@infradead.org>, acpi4asus-user <acpi4asus-user@lists.sourceforge.net>, Platform Driver <platform-driver-x86@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Linux Upstreaming Team <linux@endlessm.com>, Jian-Hong Pan <jian-hong@endlessm.com>
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On Mon, Jun 04, 2018 at 11:27:43AM +0200, Benjamin Berg wrote:
> Hi,
> 
> On Thu, 2018-05-24 at 16:33 +0800, Chris Chiu wrote:
> > I've made my change to set the brightness level directly in the
> > driver, but the
> > OSD doesn't show correctly correspond to the level value. The brightness shows
> > OK in /sys/class/led/xxxx/brighness but the OSD always shows level 0. I thought
> > GNOME should read the brightness from /sys before showing OSD?
> 
> Sorry for the late response.
> 
> There is a special mechanism to report that the HW changed the
> brightness. This works using the "brightness_hw_changed" sysfs
> attribute. So you will need to set the LED_BRIGHT_HW_CHANGED flag on
> the LED and then call led_classdev_notify_brightness_hw_changed to make
> it work.
> 
> Userspace should correctly show the OSD when this is done.

This makes sense. Userspace can't be aware of every platforms sys files,
so there needs to be a common mechanism. LED_BRIGHT_HW_CHANGED makes
sense.

-- 
Darren Hart
VMware Open Source Technology Center