Hello Andy, hello Aren,
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)". Having said
that I also dislike the "do" starting on column 0, IMHO the RHS of the
#define should be intended.
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.
While I'm in critics mode: I consider hiding a return in a macro bad
style.
Best regards
Uwe
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