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Subject: Re: [PATCH v14 13/19] leds: lp55xx: Add multicolor framework support
 to lp55xx
To:     Dan Murphy <dmurphy@ti.com>, pavel@ucw.cz
Cc:     linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Jacek Anaszewski <jacek.anaszewski@gmail.com>
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Message-ID: <7814c28c-ed38-24f0-6ff2-d89c918b617e@gmail.com>
Date:   Fri, 25 Oct 2019 20:56:29 +0200
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Sender: linux-kernel-owner@vger.kernel.org
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Dan,

On 10/25/19 8:18 PM, Dan Murphy wrote:
> Jacek
> 
> On 10/25/19 1:13 PM, Jacek Anaszewski wrote:
>> Dan,
>>
>> On 10/25/19 7:57 PM, Dan Murphy wrote:
>>> Jacek
>>>
>>> On 10/22/19 12:41 PM, Jacek Anaszewski wrote:
>>>> Dan,
>>>>
>>>> On 10/22/19 6:37 PM, Dan Murphy wrote:
>>>>> Jacek
>>>>>
>>>>> On 10/18/19 4:56 PM, Jacek Anaszewski wrote:
>>>>>> On 10/18/19 11:48 PM, Jacek Anaszewski wrote:
>>>>>>> Dan,
>>>>>> +        ret = lp5xx_parse_channel_child(child, cfg, i);
>>>>>>> I went into details of this parsing and finally came up with
>>>>>>> the code which is a bit greater in size, but IMHO cleaner.
>>>>>>> Note changes in variable naming. It is not even compile-tested.
>>>>>>>
>>>>>>> static int lp55xx_parse_common_child(struct device_node *np,
>>>>>>>                                        struct lp55xx_led_config
>>>>>>> *cfg,
>>>>>>>                                        int led_number, int *chan_nr)
>>>>>>> {
>>>>>>>            int ret;
>>>>>>>
>>>>>>>            of_property_read_string(np, "chan-name",
>>>>>>>                                    &cfg[led_number].name);
>>>>>>>            of_property_read_u8(np, "led-cur",
>>>>>>>                                &cfg[led_number].led_current);
>>>>>>>            of_property_read_u8(np, "max-cur",
>>>>>>>                                &cfg[led_number].max_current);
>>>>>>>
>>>>>>>            ret = of_property_read_u32(np, "reg", chan_nr);
>>>>>>>            if (ret)
>>>>>>>                    return ret;
>>>>>>>
>>>>>>>            if (chan_nr < 0 || chan_nr > cfg->max_chan_nr) /* side
>>>>>>> note:
>>>>>>> new
>>>>>>> max_chan_nr property needed in cfg */
>>>>>>>                    return -EINVAL;
>>>>>>>
>>>>>>>            return 0;
>>>>>>> }
>>>>>>>
>>>>>>> static int lp55xx_parse_mutli_led_child(struct device_node *np,
>>>>>>>                                            struct lp55xx_led_config
>>>>>>> *cfg,
>>>>>>>                                            int child_number,
>>>>>>>                                            int color_number)
>>>>>>> {
>>>>>>>            int chan_nr, color_id;
>>>>>>>
>>>>>>>            ret = lp55xx_parse_common_child(child, cfg, child_number,
>>>>>>> color_number,
>>>>>>>                                            &chan_nr);
>>>>>>>            if (ret)
>>>>>>>                    return ret;
>>>>>>>
>>>>>>>            ret = of_property_read_u32(child, "color", &color_id);
>>>>>>>            if (ret)
>>>>>>>                   return ret;
>>>>>>>
>>>>>>>           
>>>>>>> cfg[child_number].color_components[color_number].color_id =
>>>>>>> color_id;
>>>>>>>          
>>>>>>> cfg[child_number].color_components[color_number].output_num =
>>>>>>> chan_nr;
>>>>>>>            set_bit(color_id, &cfg[child_number].available_colors);
>>>>>>>
>>>>>>>            return 0;
>>>>>>> }
>>>>>>>
>>>>>>> staitc int lp55xx_parse_mutli_led(struct device_node *np,
>>>>>>>                                      struct lp55xx_led_config *cfg,
>>>>>>>                                      int child_number)
>>>>>>> {
>>>>>>>            struct device_node *child;
>>>>>>>            int num_colors = 0, i = 0;
>>>>>> s/, i = 0//
>>>>>>
>>>>>>>            for_each_child_of_node(np, child) {
>>>>>>>                    ret = lp55xx_parse_mutli_led_child(child, cfg,
>>>>>>> num_colors,
>>>>>>>                                                      
>>>>>>> child_number, i))
>>>>>> Replace above call with below:
>>>>>>
>>>>>> ret = lp55xx_parse_mutli_led_child(child, cfg, child_number,
>>>>>> num_colors);
>>>>>>
>>>>> I applied your DT parser patch from the v13 series.  Which eliminates
>>>>> this comment correct?
>>>> Yes, it contains this fix.
>>>>
>>> OK I added your patch and it broke a lot of the DT parsing for the
>>> LP55xx.
>>>
>>> I would prefer to stick with the original code without having to
>>> re-write this again.
>> Let me test that with Qemu first.
>>
> max_channel is never set so not sure where that is supposed to come from
> since each child device has different number of channels.  And if the
> user has to populate that information from the DT then it does not make
> sense as the user would already be aware of the number of channels. 
> This information would have to come from the child device some how and
> the children do not have access to the structure to set it.

This was my silent assumption that the child will initialize that.
And I was not thoroughly seeking the most proper place for this
property, just chose first I could think . You are free to
change its location so that it was accessible for the child.

> 
> In checking the chan_nr to the max_channels you are comparing a pointer
> to an integer.  Easy fix but did not solve the registration issues.
> 
> cfg->num_colors is not set anywhere so the registration always goes to
> base led_registration.  Unless we key off a different value to determine
> to register to multicolor class or not.  Or we default this to the
> multi_class registration to figure out how to register based on
> available_colors.

You need to add below at the end of lp55xx_parse_mutli_led():

cfg[child_number].num_colors = num_colors;

and below in led_parse_logical_led() at the end of the
"if (ret)" branch.

cfg[child_number].num_colors = 1;

> That is what I am seeing so far in my debugging and I still don't have
> it working.

I didn't pretend it was flawless, just wanted to show general idea
how I would see that.

-- 
Best regards,
Jacek Anaszewski