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

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Date:   Fri, 4 Jan 2019 22:37:58 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Vesa Jääskeläinen <dachaac@...il.com>,
        Dan Murphy <dmurphy@...com>, 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

On 1/4/19 9:12 PM, Pavel Machek wrote:
> Hi!
> 
>>> I suppose if one would just make it an array of values (separated by
>>> space) and then one file with string array of color element names and on
>>> file with maximum value array it could be within those words.
>>>
>>> The it would be something like:
>>>
>>> $ echo "23 54 32" > color
>>
>> Go ahead, but first convince Pavel, and then Greg :-)
>>
>> I'd personally would not have much against, especially that the
>> list of values will not grow for that one like in case of old patch set
>> [0] where Pavel and Greg thwarted my similar attempt.
> 
> Oh, you can get this past Pavel (and probably Greg) -- if you have a
> good reason. Performance is _not_ a good reason. You don't need to
> change LED color 50000 times a second.

We would need to do some profiling here to check if the problem exists.

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?

> If you can demonstrate a reasonable design, where user selects color
> from well-known RGB pallete and either kernel or library+kernel acts
> to set that color on the LED, we can talk.
> 
> When user asks for white, it has to be white. Exact color temperature
> does not matter. When user asks for pink, it has to be pink. Again,
> exact color does not matter; different monitors display slightly
> different colors, too
-- 
Best regards,
Jacek Anaszewski