Messages in this thread | | | Date | Sat, 24 May 2008 17:57:25 +0200 | From | "Vegard Nossum" <> | Subject | Re: kernel coding style for if ... else which cross #ifdef |
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On Sat, May 24, 2008 at 5:45 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote: > Sam Ravnborg wrote: >> >> We should actually do as you intially suggested and alwyas >> define CONFIG_FOO no matter if FOO is built-in or module. >> Because we do only want to distingush between the two in rare cases. >> >> But that is a separate patch and lets not do the same >> mistage with CFG_* >> > > I think pretty strongly that CFG_ and CONFIG_ should be exactly parallel. > If you want to change the meaning of CONFIG_X in the presence of modules, > then change CFG_X at the same time. Making them have different meanings > will just confuse anyone wanting to convert #ifdef CONFIG_ code into > if(CFG_) code. > >> I cooked up following patch - but I have not test-build a kernel yet. >> We may use CFG_* here and there and clash is not good. >> > > I have to say I'm not very keen on the CFG_* prefix. It doesn't have any > inherent meaning and just looks like a redundant abbreviation of CONFIG_; > something which actually expresses the notion that it's always a > compile-time constant would be better. Not that I have any particularly > good alternatives: CONST_? CCONST_? CONFIG_X_VAL? KCONFIG_? KONFIG_? > KCONST_?
Don't know if this is really my place, but I could not agree more with your characterisation of the CFG_* prefix and I will make the following suggestion:
Why not use all-lowercase config_* names? It seems elegant, and fits in with the notion that these are to be used not as macros, but as ordinary constants.
(The only disadvantage I can see is that they will stand out less. But I don't know how great the disadvantage is.)
You could even go further and make them real constants, something along the lines of:
enum config_value { no, yes, mod };
static const enum config_value config_lockdep_support = yes;
(I believe the "static const" will prevent emission of this symbol in the object file -- though I am not certain.)
You can now also test for specific values, e.g. if (config_scsi_wait_scan == mod), in addition to simply testing the truth value.
That concludes my suggestion.
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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