linux-kernel - Re: [PATCH v2 04/11] leds: aw200xx: calculate dts property display

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Date:   Thu, 19 Oct 2023 22:25:01 +0300
From:   George Stark <gnstark@...utedevices.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Dmitry Rokosov <ddrokosov@...utedevices.com>
CC:     <lee@...nel.org>, <pavel@....cz>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <kernel@...rdevices.ru>, <rockosov@...il.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-leds@...r.kernel.org>
Subject: Re: [PATCH v2 04/11] leds: aw200xx: calculate dts property
 display_rows in driver

Hello Andy

On 10/19/23 12:01, Andy Shevchenko wrote:
> On Wed, Oct 18, 2023 at 9:30 PM Dmitry Rokosov
> <ddrokosov@...utedevices.com> wrote:
>>
>> From: George Stark <gnstark@...utedevices.com>
>>
>> Get rid of device tree property "awinic,display-rows" and calculate it
>> in driver using led definition nodes. display-row actually means number
>> of current switches and depends on how leds are connected to the device.
> 
> Still the commit message does not answer the question why it's safe
> for the users that have this property enabled in their DTBs (note B
> letter).
> 


> ...
> 
>> +       device_for_each_child_node(dev, child) {
>> +               u32 source;
>> +               int ret;
>> +
>> +               ret = fwnode_property_read_u32(child, "reg", &source);
>> +               if (ret || source >= chip->cdef->channels)
> 
> Perhaps a warning?
> 
>      dev_warn(dev, "Unable to read from %pfw or apply a source channel
> number\n", child);

I skipped the warning intentionally because we have just the same loop 
several steps below and with the same check. There we have all proper 
warnings and aw200xx_probe_get_display_rows was intended to be short and 
lightweight. I'll redesign it to be even more simple.

> 
>> +                       continue;
>> +
>> +               max_source = max(max_source, source);
>> +       }
> 
> ...
> 
>> +       chip->display_rows = max_source / chip->cdef->display_size_columns + 1;
>> +       if (!chip->display_rows) {
>> +               dev_err(dev, "No valid led definitions found\n");
>> +               return -EINVAL;
> 
> So, this part is in ->probe() flow only, correct? If so,
>    return dev_err_probe(...);
> 
>> +       }
> 
> ...
> 
>> +       if (aw200xx_probe_get_display_rows(dev, chip))
>> +               return -EINVAL;
> 
> Why is the error code shadowed?
> 

-- 
Best regards
George