From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH 3/3] devicetree: Add led-backlight binding Date: Wed, 26 Aug 2015 09:07:42 +0200 Message-ID: <55DD65BE.4050308@samsung.com> References: <1440502442-19531-1-git-send-email-tomi.valkeinen@ti.com> <1440502442-19531-4-git-send-email-tomi.valkeinen@ti.com> <55DC700C.4030802@samsung.com> <55DC8C9D.4050007@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mailout4.w1.samsung.com ([210.118.77.14]:9316 "EHLO mailout4.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756534AbbHZHHq (ORCPT ); Wed, 26 Aug 2015 03:07:46 -0400 In-reply-to: <55DC8C9D.4050007@ti.com> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Tomi Valkeinen Cc: Jingoo Han , Lee Jones , linux-leds@vger.kernel.org, linux-fbdev@vger.kernel.org, Andrew Lunn On 08/25/2015 05:41 PM, Tomi Valkeinen wrote: > > > On 25/08/15 16:39, Jacek Anaszewski wrote: > >>> +Example: >>> + >>> + backlight { >>> + compatible = "led-backlight"; >>> + leds = <&backlight_led>; >>> + >>> + brightness-levels = <0 4 8 16 32 64 128 255>; >> >> brightness level is not a suitable unit for describing LED brightness >> in a Device Tree, as it is not a physical unit. We have led-max-microamp >> property for this, expressed in microamperes, please refer to [0] from >> linux-next. > > Hmm, ok, but what should the driver do with microamperes? As far as I > see, "enum led_brightness" (which is between 0-255) is used to set the > brightness to LEDs. I don't see any function accepting microamperes. This is implementation detail. You can convert microamperes to enum led_brightness in the driver. Please refer to the discussion [1]. >>> + default-brightness-level = <6>; >> >> This also should be microamperes. > > This is an index to the above brightness-levels array. It's not LED > brightness, but backlight brightness, between 0 and > ARRAY_SIZE(brightness-levels) - 1. You could skip "-level" postfix and have default brightness in microamperes. [1] http://www.spinics.net/lists/linux-leds/msg03416.html -- Best Regards, Jacek Anaszewski