linux-kernel - Re: [PATCH v2] pinmux: add a driver for the CSR SiRFprimaII pinmux

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Date:	Sat, 08 Oct 2011 15:08:27 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Barry Song <21cnbao@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	linus.walleij@...ricsson.com, linux-kernel@...r.kernel.org,
	workgroup.linux@....com, Rongjun Ying <rongjun.ying@....com>,
	Barry Song <Baohua.Song@....com>
Subject: Re: [PATCH v2] pinmux: add a driver for the CSR SiRFprimaII pinmux

On Saturday 08 October 2011 19:58:23 Barry Song wrote:
> > You can probably simplify this and other things with
> > preprocessor macros if you want to, like:
> >
> > #define SIRF_FUNC_ENTRY(a) \
> > { .name = "##a##", .pins = ##a##_pins, .num_pins =
> > ARRAY_SIZE(##a##_pins), .padmux = &##a##_padmux }
> >
> > Then just:
> >
> > static const struct sirfsoc_pinmux_func sirfsoc_pinmux_funcs[] = {
> >     SIRF_FUNC_ENTRY(lcd_16bits),
> >
> >
> > The macro syntax is probably wrong, the preprocessor always
> > craze me out, but you get the idea.
> 
>  :-)  .name = "##a##"  should be changed to .name = #a
> 
> #name will convert name into a string "name"
> 

Better don't use string concatenation at all if you can avoid it.

A generic macro like

#define SIRF_PINMUX(_name, _pins, _padmux) \
	{ .name = (_name), .pins = (_pins), \
	  .num_pins = ARRAY_SIZE(_pins), padmux = (_padmux), }

is both very easy to understand for someone reading it casually and
lets you actually grep for where the identifiers are being used.

> static const struct sirfsoc_pinmux_func sirfsoc_pinmux_funcs[] = {
>     SIRF_FUNC_ENTRY(lcd_16bits),

for the first time, you have no clue what that does, but

static const struct sirfsoc_pinmux_func sirfsoc_pinmux_funcs[] = {
	SIRF_PINMUX("lcd_16bits", lcd_16bits_pins, &lcd_16bits_padmux),
	...
};

Makes it very clear what you are referencing here and needs no extra lines.

	Arnd
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