From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v4 3/4] leds: core: add documentation for color extension Date: Tue, 01 Mar 2016 10:25:57 +0100 Message-ID: <56D56025.4080201@samsung.com> References: <56CF7C85.7030005@gmail.com> <56D46E58.5070508@samsung.com> <56D4A91C.30309@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mailout4.w1.samsung.com ([210.118.77.14]:61644 "EHLO mailout4.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751209AbcCAJ0A (ORCPT ); Tue, 1 Mar 2016 04:26:00 -0500 Received: from eucpsbgm2.samsung.com (unknown [203.254.199.245]) by mailout4.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O3C00KMQSV9TV50@mailout4.w1.samsung.com> for linux-leds@vger.kernel.org; Tue, 01 Mar 2016 09:25:57 +0000 (GMT) In-reply-to: <56D4A91C.30309@gmail.com> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Heiner Kallweit Cc: linux-leds@vger.kernel.org On 02/29/2016 09:25 PM, Heiner Kallweit wrote: > Am 29.02.2016 um 17:14 schrieb Jacek Anaszewski: >> On 02/25/2016 11:13 PM, Heiner Kallweit wrote: >>> Document the color extension in Documentation/leds/leds-class.txt >>> >>> Signed-off-by: Heiner Kallweit >>> --- >>> v2: >>> - introduced to patch series >>> v3: >>> - document extension in more detail >>> v4: >>> - Better explain why flag LED_SET_HUE_SAT is needed >>> --- >>> Documentation/leds/leds-class.txt | 27 ++++++++++++++++++++++----- >>> 1 file changed, 22 insertions(+), 5 deletions(-) >>> >>> diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt >>> index d406d98..b1e4cba 100644 >>> --- a/Documentation/leds/leds-class.txt >>> +++ b/Documentation/leds/leds-class.txt >>> @@ -8,6 +8,22 @@ LED is defined in max_brightness file. The brightness file will set the brightne >>> of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware >>> brightness support so will just be turned on for non-zero brightness settings. >>> >>> +If a driver uses the colour extension of the LED core then the brightness >>> +file can be used to set hue / saturation / value. The brightness value is >>> +interpreted as: <0000000F> >>> +Usage of the least byte is identical to monochrome mode. Saturation can be >>> +0-255 and hue 0-251 (Colour circle is mapped to 0-252). >>> +If hue and saturation both are 0 the current colour is preserved and only >>> +the brightness is set. This ensures backwards compatibility with monochrome >>> +mode, e.g. for led_set_brightness() calls from triggers. >>> +However we might want to have the option to set all HSV components, even >>> +if hue and saturation both are 0 (e.g. via brightness sysfs attribute). >>> +Use case: Set color to white (hue = 0 and saturation = 0). >>> +Therefore the default behaviour can be overridden with flag F (LED_SET_HUE_SAT). >>> +If this flag is set then hue and saturation are not checked for being 0 and >>> +the color components are set unconditionally. Example: >>> +0x010000ff sets the LED to white color with full brightness. >> >> I was thinking especially about highlighting the use case when we set >> different hue and sat for different LEDs that are registered on some >> trigger, and a driver that is currently unaware of LED RGB extension can >> set only brightness and the LEDs will react with changing their >> colors but each of them in different manner, according to the hue >> and sat set. >> > I have to admit that I have a hard time trying to understand what you mean. I was writing this in a hurry - sorry about that. > With > "a driver that is currently unaware of LED RGB extension can set only brightness" > you mean a driver calling led_trigger_event? > Arguments to led_trigger_event are always <= LED_FULL what means that the (potential) > color of all LEDs attached to the trigger isn't touched. Changing brightness in HSV model influences resultant color, doesn't it? >>> The class also introduces the optional concept of an LED trigger. A trigger >>> is a kernel based source of led events. Triggers can either be simple or >>> complex. A simple trigger isn't configurable and is designed to slot into >>> @@ -45,11 +61,12 @@ Is currently of the form: >>> >>> "devicename:colour:function" >>> >>> -There have been calls for LED properties such as colour to be exported as >>> -individual led class attributes. As a solution which doesn't incur as much >>> -overhead, I suggest these become part of the device name. The naming scheme >>> -above leaves scope for further attributes should they be needed. If sections >>> -of the name don't apply, just leave that section blank. >>> +If the colour extension is used hsv / rgb can be used instead of a specific >>> +colour. There have been calls for LED properties such as colour to be >>> +exported as individual led class attributes. As a solution which doesn't >>> +incur as much overhead, I suggest these become part of the device name. >>> +The naming scheme above leaves scope for further attributes should they be >>> +needed. If sections of the name don't apply, just leave that section blank. >>> >>> >>> Brightness setting API >>> >> >> > > > -- Best regards, Jacek Anaszewski