linux-kernel - Re: [PATCH v4 4/6] iio: light: stk3310: use dev_err

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Message-ID: <CAHp75Vfm_7Gq5a-v1+=WCq2w0Am0VF+z_NPenHbuvV-Mj+MX4A@mail.gmail.com>
Date: Tue, 12 Nov 2024 14:31:57 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Uwe Kleine-König <u.kleine-koenig@...libre.com>
Cc: Aren <aren@...cevolution.org>, Jonathan Cameron <jic23@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Kaustabh Chakraborty <kauschluss@...root.org>, Barnabás Czémán <trabarni@...il.com>, 
	Ondrej Jirman <megi@....cz>, linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, Dragan Simic <dsimic@...jaro.org>, 
	phone-devel@...r.kernel.org
Subject: Re: [PATCH v4 4/6] iio: light: stk3310: use dev_err_probe where possible

On Tue, Nov 12, 2024 at 12:15 PM Uwe Kleine-König
<u.kleine-koenig@...libre.com> wrote:
> On Mon, Nov 11, 2024 at 11:44:51AM +0200, Andy Shevchenko wrote:
> > On Sun, Nov 10, 2024 at 04:34:30PM -0500, Aren wrote:
> > > On Sun, Nov 10, 2024 at 09:52:32PM +0200, Andy Shevchenko wrote:
> > > > Sun, Nov 10, 2024 at 02:14:24PM -0500, Aren kirjoitti:
> >
> > You can do it differently
> >
> > #define STK3310_REGFIELD(name)                                                        \
> > do {                                                                          \
> >       data->reg_##name =                                                      \
> >               devm_regmap_field_alloc(dev, regmap, stk3310_reg_field_##name); \
> >       if (IS_ERR(data->reg_##name))                                           \
> >               return dev_err_probe(dev, PTR_ERR(data->reg_##name),            \
> >                                    "reg field alloc failed.\n");              \
> > } while (0)
> >
> > > #define STK3310_REGFIELD(name) ({                                           \
> > >     data->reg_##name = devm_regmap_field_alloc(dev, regmap,                 \
> > >                                                stk3310_reg_field_##name);   \
> > >     if (IS_ERR(data->reg_##name))                                           \
> > >             return dev_err_probe(dev, PTR_ERR(data->reg_##name),            \
> > >                                  "reg field alloc failed\n");               \
> > > })
> >
> > I am against unneeded use of GNU extensions.
> >
> > > > > replacing "do { } while (0)" with "({ })" and deindenting could make
> > > > > enough room to clean this up the formatting of this macro though.
> > > >
> > > > do {} while (0) is C standard, ({}) is not.
> > >
> > > ({ }) is used throughout the kernel, and is documented as such[1]. I
> > > don't see a reason to avoid it, if it helps readability.
> >
> > I don't see how it makes things better here, and not everybody is familiar with
> > the concept even if it's used in the kernel here and there. Also if a tool is
> > being used in one case it doesn't mean it's suitable for another.
>
> Just to throw in my subjective view here: I don't expect anyone with
> some base level knowledge of C will have doubts about the semantics of
> ({ ... }) and compared to that I find do { ... } while (0) less optimal,
> because it's more verbose and when spotting the "do {" part, the
> semantic only gets clear when you also see the "while (0)".

Seems we have to agree on a disagreement.

> Having said
> that I also dislike the "do" starting on column 0, IMHO the RHS of the
> #define should be intended.

This argument I kinda accept.

> So if you ask me, this is not an unneeded use of an extension. The
> extension is used to improve readabilty and I blame the C standard to
> not support this syntax.

Here I agree with you.

> While I'm in critics mode: I consider hiding a return in a macro bad
> style.

So, summarizing the discussion we have a split, hence Jonathan is our
arbiter here to judge.

-- 
With Best Regards,
Andy Shevchenko