Re: kernel coding style for if ... else which cross #ifdef
From: Jeremy Fitzhardinge
Date: Sat May 24 2008 - 10:36:36 EST
Sam Ravnborg wrote:
I assume you wanted to say:
#undef CONFIG_FOO
#define CFG_FOO 1
#define CONFIG_FOO_MODULE
#define CFG_FOO_MODULE 1
Because then the CONFIG_* is not changed
and we do not want to change that.
Yeah, I didn't intend to change the meaning of CONFIG_FOO.
I'm not fully convinced about:
#define CFG_FOO 1
But on the other hand it is only in odd
cases we distingush between built-in and module.
So it makes most sense.
I think CONFIG_ and CFG_ should be exact parallels, so if CONFIG_FOO is
undefined, CFG_FOO should be 0.
Not sure what CFG_* should be for string/numeric options. Probably "1"
if the value is defined, "0" if not, with CONFIG_* being the actual
value (so a CONFIG_ value of 0 is distinguishable from not defined).
For non-boolean/tristate values we simply skip CFG_ values - thats
the most simple approach.
I suppose, but it might be useful to know whether a constant is present:
if (CFG_THINGY_LIMIT && x > CONFIG_THINGY_LIMIT) {...}
(which fails if CONFIG_THINGY_LIMIT is undefined, so I guess it still
doesn't work very well).
J
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