[RFC 4/5] pinctrl: SPEAr: Add gpio ranges support

[arnd@arndb.de (Arnd Bergmann)]

On Monday 07 May 2012, Linus Walleij wrote:
> Hm first I wonder what i2c0 and ssp0 have to do with GPIO...
> Well whatever, maybe split out a special patch just adding the
> groups?
> 
> Please cut down this code by using a clever macro:
> 
> #define SPEAR_PCTL_GRP(a,b) \
> { \
>     .pins =  a##_pins, \
>     .npins = ARRAY_SIZE(a##_pins), \
>     .muxreg = { \
>         .reg = PAD_FUNCTION_EN_2, \
>         .mask PMX_##b##_MASK, \
>         .val = 0, \
>     }, \
> }
> 
> Then:
> 
> static struct spear_gpio_pingroup spear1310_gpio_pingroup[] = {
>     SPEAR_PCTL_GRP(i2c0, I2C0),
>     SPEAR_PCTL_GRP(ssp0, SSP0),
>     SPEAR_PCTL_GRP(ssp0_cs0, SSP0_CS0),
>     (...)
> };
> 
> (You get the picture.)

If you allow me to give my 2 cents, I would recommend the exact opposite
in general: resist the urge to use complex macros for everything!

When that gets too hard, please at least use macros that do not concatenate
C identifies because that makes it really hard to grep for where a constant
gets used. 

A more acceptable macro would be 

#define SPEAR_PCTL_GRP(_pins, _mask) \
{ \
	.pins =  _pins, \
	.npins = ARRAY_SIZE(_pins), \
	.muxreg = { \
	        .reg = PAD_FUNCTION_EN_2, \
	        .mask _val, \
	        .val = 0, \
	}, \
}

but open-coding is generally ok too. Note that you can sometimes save a lot
of lines if you don't first define all those constants as macros but
treat a table like this as the place where you put the raw numbers
from the data sheet, if that the only code location in which they are
used.

	Arnd