linux-kernel - Re: [PATCH v2] platform/x86: asus-wmi: Add keyboard backlight toggle support

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Message-ID: <20180605015900.GC47042@localhost.localdomain>
Date:   Mon, 4 Jun 2018 18:59:00 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Benjamin Berg <benjamin@...solutions.net>
Cc:     Chris Chiu <chiu@...lessm.com>, Daniel Drake <drake@...lessm.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Corentin Chary <corentin.chary@...il.com>,
        Andy Shevchenko <andy@...radead.org>,
        acpi4asus-user <acpi4asus-user@...ts.sourceforge.net>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>,
        Jian-Hong Pan <jian-hong@...lessm.com>
Subject: Re: [PATCH v2] platform/x86: asus-wmi: Add keyboard backlight toggle
 support

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