linux-kernel - Re: [PATCH v5 2/3] platform/chrome: Add Wilco EC keyboard backlight LEDs support

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Date:   Thu, 4 Apr 2019 21:52:10 +0200
From:   Pavel Machek <pavel@....cz>
To:     Nick Crews <ncrews@...omium.org>
Cc:     enric.balletbo@...labora.com, bleung@...omium.org,
        linux-leds@...r.kernel.org, jacek.anaszewski@...il.com,
        alexandre.belloni@...tlin.com, a.zummo@...ertech.it,
        linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        dlaurie@...omium.org, sjg@...gle.com, groeck@...gle.com,
        dtor@...gle.com
Subject: Re: [PATCH v5 2/3] platform/chrome: Add Wilco EC keyboard backlight
 LEDs support

On Thu 2019-04-04 11:10:08, Nick Crews wrote:
> The EC is in charge of controlling the keyboard backlight on
> the Wilco platform. We expose a standard LED class device at
> /sys/class/leds/platform::kbd_backlight. This driver is modeled
> after the standard Chrome OS keyboard backlight driver at
> drivers/platform/chrome/cros_kbd_led_backlight.c
> 
> Some Wilco devices do not support a keyboard backlight. This
> is checked via wilco_ec_keyboard_leds_exist() in the core driver,
> and a platform_device will only be registered by the core if
> a backlight is supported.
> 
> After an EC reset the backlight could be in a non-PWM mode.
> Earlier in the boot sequence the BIOS should send a command to
> the EC to set the brightness, so things **should** be set up,
> but we double check in probe() as we query the initial brightness.
> If not set up, then set the brightness to 0.
> 
> Since the EC will never change the backlight level of its own accord,
> we don't need to implement a brightness_get() method.
...
> Signed-off-by: Nick Crews <ncrews@...omium.org>
> Acked-by: Jacek Anaszewski <jacek.anaszewski@...il.com>

Acked-by: Pavel Machek <pavel@....cz>

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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