linux-kernel - Re: [PATCH 2/2] regulator: rt5759: Add support for Richtek RT5759 DCDC converter

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Date:   Sat, 26 Mar 2022 08:58:47 +0800
From:   ChiYuan Huang <u0084500@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        cy_huang <cy_huang@...htek.com>, gene_chen@...htek.com,
        lkml <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/2] regulator: rt5759: Add support for Richtek RT5759
 DCDC converter

Krzysztof Kozlowski <krzk@...nel.org> 於 2022年3月26日 週六 上午12:08寫道：
>
> On 25/03/2022 17:05, Mark Brown wrote:
> > On Fri, Mar 25, 2022 at 04:55:25PM +0100, Krzysztof Kozlowski wrote:
> >
> >> You mention board, some of_device_get_match_data() so you talk about
> >> runtime. maybe_unused is not about runtime. It is about build time.
> >
> >> The code you sent cannot have this structure unused. If you think
> >> otherwise, please provide argument, but not about runtime (again). You
> >> can for example build it without OF and see...
> >
> > If you use of_match_ptr() in the struct device (which is good practice,
> > didn't check if this driver does it) then that causes the ID table to be
> > unreferenced as of_match_ptr() compiles to NULL when !OF.
>
> Yep, then the case is obvious, but the driver does not use it.
>
> +static struct i2c_driver rt5759_driver = {
> +       .driver = {
> +               .name = "rt5759",
> +               .of_match_table = rt5759_device_table,
>
> Therefore the of_device_id cannot be unused, so __maybe_unused is not
> correct. This can be fixed in two different ways, which we did not
> discuss yet...
>
As my past experience, '__maybe_unused' must be added to fix W=1 build
warning when OF=n
You can refer to the below link.
https://lore.kernel.org/lkml/1598234713-8532-1-git-send-email-u0084500@gmail.com/

And it's based on 'of_match_ptr' is used.

I tried to remove only __maybe_unused and build with x86 config  that
CONFIG_OF=n.
There's no warning or error message when compiling the rt5759 source code.

If so, I will remove only '__maybe_unused'.
May I ask whether 'of_match_ptr'  need to be added or not?

> Best regards,
> Krzysztof