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

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Date:   Sat, 6 Apr 2019 10:41:57 +0200
From:   Pavel Machek <pavel@....cz>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Nick Crews <ncrews@...omium.org>, 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 Fri 2019-04-05 13:15:34, Guenter Roeck wrote:
> On Thu, Apr 04, 2019 at 11:10:08AM -0600, 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.
> > 
> > v5 changes:
> > -Rename the LED device to "platform::kbd_backlight", to
> > denote that this is the built-in system keyboard.
> > 
> 
> NACK.

Please keep it as it is, it is okay.

> Per Documentation/leds/leds-class.txt, LED devices are named
> 	"devicename:colour:function"

You failed to follow threads explaining this is being changed, even
when I pointed you at them. What you are doing here is not helpful.

> This document also states "The naming scheme above leaves scope
> for further attributes should they be needed". It does not permit,
> however, to redefine one of the fields to mean "location", much less
> the declaration that a devicename of "platform" shall refer to an
> "internal" backlight, or that there shall be no more than one
> "internal" backlight in a given system.

"platform" is as good devicename as "wilco" or "chromeos".
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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