linux-kernel - Re: [RESEND PATCH v3 4/4] leds: Add a multicolor LED driver to group monochromatic LEDs

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Date:   Fri, 7 Oct 2022 08:34:23 +0200
From:   Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     <pavel@....cz>, <robh+dt@...nel.org>,
        <sven.schwermer@...ruptive-technologies.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <johan+linaro@...nel.org>,
        <marijn.suijten@...ainline.org>, <bjorn.andersson@...aro.org>,
        <linux-leds@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sha@...gutronix.de>
Subject: Re: [RESEND PATCH v3 4/4] leds: Add a multicolor LED driver to group
 monochromatic LEDs


On 17/09/2022 10:37, Andy Shevchenko wrote:
> On Sat, Sep 17, 2022 at 11:14 AM Jean-Jacques Hiblot
> <jjhiblot@...phandler.com> wrote:
>> By allowing to group multiple monochrome LED into multicolor LEDs,
>> all involved LEDs can be controlled in-sync. This enables using effects
>> using triggers, etc.
> ...
>
>> +config LEDS_GRP_MULTICOLOR
>> +       tristate "Multi-color LED grouping support"
>> +       help
>> +         This option enables support for monochrome LEDs that are
>> +         grouped into multicolor LEDs.
> What will be the module name in case of "m" choice?
>
> ...
>
>> +       struct led_mcg_priv *priv =
>> +               container_of(mc_cdev, struct led_mcg_priv, mc_cdev);
> One line?
>
> ...
>
>> +               /*
>> +                * Scale the intensity according the max brightness of the
>> +                * monochromatic LED
> Usually we put a grammar period at the end of sentences in multi-line comments.
>
>> +                */
> ...
>
>> +               actual_led_brightness = DIV_ROUND_CLOSEST(
>> +                       mono->max_brightness * mc_cdev->subled_info[i].brightness,
>> +                       mc_cdev->led_cdev.max_brightness);
> Can you fix an indentation, so it won't leave the line ending by open
> parenthesis? I believe with the help of a temporary variable it can be
> easily achieved.
Could be done but I have no good name for the variable and I think it 
would just make things harder to understand. In that form I think it is 
clear that this is a cross-multiplication.
>
> ...
>
>> +       for (;;) {
>> +               struct led_classdev *led_cdev;
>> +               led_cdev = devm_of_led_get(dev, count);
> Why _of_ variant? Please, make this OF independent since it's
> pretending to cover not only OF-based systems.

This is not OF independent. It could be, but that will wait until 
someone needs it. I don't know much about ACPI and have no hardware to 
test it on.

I'll add the missing  dependency on OF in the Kconfig.

>
>
>> +               if (IS_ERR(led_cdev)) {
>> +                       /* Reached the end of the list ? */
>> +                       if (PTR_ERR(led_cdev) == -ENOENT)
>> +                               break;
> Looks like the above needs an _optional() variant
>
>> +                       return dev_err_probe(dev, PTR_ERR(led_cdev),
>> +                                            "Unable to get led #%d", count);
>> +               }
> ...
>
>> +               priv->monochromatics = devm_krealloc(dev, priv->monochromatics,
>> +                                       count * sizeof(*priv->monochromatics),
>> +                                       GFP_KERNEL);
> This needs at minimum to use one of the helpers from overflow.h,
> ideally you may implement devm_krealloc_array() as a suitable wrapper
> for that.
>
>> +               if (!priv->monochromatics)
>> +                       return -ENOMEM;
> ...
>
>> +       subled = devm_kzalloc(dev, count * sizeof(*subled), GFP_KERNEL);
> NIH devm_kcalloc()
>
>> +       if (!subled)
>> +               return -ENOMEM;
> --
> With Best Regards,
> Andy Shevchenko