linux-kernel - Re: [PATCH 2/2] leds: lp5024: Add the LP5024/18 RGB LED driver

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Message-ID: <0982f9c3-b5df-7131-8d5a-761adefd389d@ti.com>
Date:   Mon, 7 Jan 2019 15:15:02 -0600
From:   Dan Murphy <dmurphy@...com>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Vesa Jääskeläinen <dachaac@...il.com>,
        Pavel Machek <pavel@....cz>
CC:     <robh+dt@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-leds@...r.kernel.org>
Subject: Re: [PATCH 2/2] leds: lp5024: Add the LP5024/18 RGB LED driver

Jacek

On 1/7/19 3:13 PM, Jacek Anaszewski wrote:
> Hi Vesa,
> 
> On 1/5/19 1:39 AM, Vesa Jääskeläinen wrote:
>> Hi Jacek,
>>
>> On 04/01/2019 23.37, Jacek Anaszewski wrote:
>>> But, aside from that hypothetic issue, we need a solution for
>>> LEDn_BRIGHTNESS feature of lp5024, i.e. setting color intensity
>>> via a single register write. How would you propose to address that?
>>
>> You could model it to something like this in device tree:
>>
>> led-module @ <i2c-address> {
>>      compatible = "lp5024";
>>
>>      // There is in hardware setup to use either linear or
>>      // logarithmic scaling:
>>      //enable-logarithmic-brightness;
>>
>>      led0 {
>>          // this will create led instance for LED0 in lp5024
>>          label = "lp-led0";
>>
>>          // This specifies LED number within lp5024
>>          led-index = <0>;   // set output-base as 0*3 == 0
>>
>>          element-red {
>>              // refers to OUT0
>>              output-offset = <0>;
>>          };
>>
>>          element-green {
>>              // refers to OUT1
>>              output-offset = <1>;
>>          };
>>
>>          element-blue {
>>              // refers to OUT2
>>              output-offset = <2>;
>>          };
>>
>>      };
>>
>>      led1 {
>>          // this will create led instance for LED1 in lp5024
>>          label = "lp-led1";
>>
>>          // This specifies LED number within lp5024
>>          led-index = <1>;   // set output-base as 1*3 == 3
>>
>>          element-red {
>>              // refers to OUT3
>>              output-offset = <0>;
>>          };
>>
>>          element-green {
>>              // refers to OUT4
>>              output-offset = <1>;
>>          };
>>
>>          element-blue {
>>              // refers to OUT5
>>              output-offset = <2>;
>>          };
>>
>>      };
>>
>>      bank-led {
>>          // this will create led instance for bank leds in lp5024
>>          label = "lp-bank-led";
>>
>>          // configured bank led configuration
>>          led-index = <2 3 4 5 6 7>;
>>          // As here is list of led-indices this entry is
>>          // assumed to be bank configuration. Bank mode is enable
>>          // for the indices.
>>
>>          // set output-base as BANK A
>>
>>          element-red {
>>              // refers to BANK A
>>              output-offset = <0>;
>>          };
>>
>>          element-green {
>>              // refers to BANK B
>>              output-offset = <1>;
>>          };
>>
>>          element-blue {
>>              // refers to BANK C
>>              output-offset = <2>;
>>          };
>>      };
>> };
>>
>> This would then create three led instances and each led instance has brightness setting and that goes straight to hardware.
>>
>> If one would want to override hardware control for brightness then I suppose you would define in led node something like:
>>
>>      brightness-model = "hsl"
>>
>> This would then pick red, green and blue elements for hsl calculations and others color elements for linear. LED specific hardware brightness would then be either 0 or 0xFF depending if all of LED color elements are zero or not.
>>
>> Would that kind of model work?
> 
> I'd prefer to have single RGB LED device. And your DT design
> is unnecessarily complex and a bit confusing.

+1 to that comment

> 
> Also, you provided scarce information about sysfs interface.
> It would be nice to see the sequence of commands.
> 


-- 
------------------
Dan Murphy