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

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Date:   Wed, 19 Dec 2018 14:41:04 -0600
From:   Dan Murphy <dmurphy@...com>
To:     Pavel Machek <pavel@....cz>
CC:     <robh+dt@...nel.org>, <jacek.anaszewski@...il.com>,
        <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

Pavel

On 12/19/2018 02:10 PM, Pavel Machek wrote:
> On Wed 2018-12-19 13:41:18, Dan Murphy wrote:
>> Pavel
>>
>> Thanks for the review.
>>
>> On 12/19/2018 01:34 PM, Pavel Machek wrote:
>>> Hi!
>>>
>>>> +static DEVICE_ATTR_WO(ctrl_bank_a_mix);
>>>> +static DEVICE_ATTR_WO(ctrl_bank_b_mix);
>>>> +static DEVICE_ATTR_WO(ctrl_bank_c_mix);
>>>> +
>>>> +static struct attribute *lp5024_ctrl_bank_attrs[] = {
>>>> +	&dev_attr_ctrl_bank_a_mix.attr,
>>>> +	&dev_attr_ctrl_bank_b_mix.attr,
>>>> +	&dev_attr_ctrl_bank_c_mix.attr,
>>>> +	NULL
>>>> +};
>>>> +ATTRIBUTE_GROUPS(lp5024_ctrl_bank);
>>>
>>> ...
>>>> +
>>>> +static DEVICE_ATTR_WO(led1_mix);
>>>> +static DEVICE_ATTR_WO(led2_mix);
>>>> +static DEVICE_ATTR_WO(led3_mix);
>>>> +
>>>> +static struct attribute *lp5024_led_independent_attrs[] = {
>>>> +	&dev_attr_led1_mix.attr,
>>>> +	&dev_attr_led2_mix.attr,
>>>> +	&dev_attr_led3_mix.attr,
>>>> +	NULL
>>>> +};
>>>> +ATTRIBUTE_GROUPS(lp5024_led_independent);
>>>
>>> Ok, so you are adding new sysfs files. Are they _really_ neccessary?
>>> We'd like to have uniform interfaces for the leds.
>>
>> Yes I am adding these for this driver.
>> They adjust the individual brightness of each LED connected (what the HW guys called mixing).
>>
>> The standard brightness sysfs adjusts all 3 LEDs simultaneously so that all 3 LEDs brightness are
>> uniform.
> 
> 1 LED, 1 brightness file... that's what we do. Why should this one be different?
> 

Yes I understand this and 1 DT child node per LED out but...

This device has a single register to control 3 LEDs brightness as a group and individual brightness
registers to control the LEDs independently to mix the LEDs to a specific color.

There needs to be a way to control both so that developers can mix and adjust the individual RGB and
then control the brightness of the group during run time without touching the "mixing" value.

I don't think a user needs nor would want to have 24 different LED nodes with 24 different brightness files.
Or with the LP5036 that would have 36 LED nodes.

Table 1 in the data sheet shows how the outputs map to the control banks to the LED registers.

Dan


>> I did not think these belonged in the dt as they should be user space configurable
>>
>>>
>>> If they are neccessary, we need documentation for them.
>>
>> Sure I have no problem documenting them but where do I do that?
>> I am assuming Documentation/leds/leds-lp5024.txt
> 
> Documentation/abi/...
> 
> 									Pavel
> 


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