linux-kernel - Re: help for kernel initcall section (init.h)

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Message-ID: <1314022627.68014.YahooMailNeo@web162017.mail.bf1.yahoo.com>
Date:	Mon, 22 Aug 2011 07:17:07 -0700 (PDT)
From:	Pintu Agarwal <pintu_agarwal@...oo.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: help for kernel initcall section (init.h)

         


----- Original Message -----
> From: Américo Wang <xiyou.wangcong@...il.com>
> To: Pintu Agarwal <pintu_agarwal@...oo.com>
> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
> Sent: Monday, 22 August 2011 2:38 PM
> Subject: Re: help for kernel initcall section (init.h)
> 
> On Sun, Aug 21, 2011 at 11:54 AM, Pintu Agarwal <pintu_agarwal@...oo.com> 
> wrote:
>> Hi,
>> 
>> I need some help in modifying initcall section in init.h.
>> 
>> That is :
>> 
>> #define __define_initcall(level,fn,id) \
>>  static initcall_t __initcall_##fn##id __used \
>>  __attribute__((__section__(".initcall" level 
> ".init"))) = fn
>> 
>> I have to create two different kinds (and later more) of init section and 
> use one of them based on some condition.
>> For example, I have one init section for normal mode and one init section 
> for charger mode.
>> During charger mode, I do not have to execute all the initcall so a 
> charger.initcall is create with lesser init function.
>> The charger initcall section is as follows:
>> #define __define_charger_initcall(level,fn,id) \
>>  static initcall_t __charger_initcall_##fn##id __used \
>>  __attribute__((__section__(".charger.initcall" level 
> ".init"))) = fn
>> 
>> 
>> Now the problem is that during compile time both of them needs to be 
> polulated based on CHARGER_MODE is enabled or disabled.
>> How can this decision be taken during compile time under the macro 
> "__define_initcall" ??
>> 
>> Something like :
>> 
>> #define __define_initcall(level,fn,id)     \
>>                                                        static initcall_t 
> __initcall_##fn##id __used \
>>                                                        
> __attribute__((__section__(".initcall" level ".init"))) = 
> fn  \
>>                                                        #if 
> defined(CHARGER_MODE)  \
>>                                                        static initcall_t 
> __charger_initcall_##fn##id __used  \
>> 
>                                                        __attribute__((__section__(".charger.initcall" 
> level ".init"))) = fn   \
>>                                                        #endif
> 
> Hi,
> 
> Why not
> 
> X_initcall(foo_initcall);
> #ifdef CHARGER_MODE
> X_initcall(foo_charger_initcall);
> #endif
> 
> ?
>

No the requirement is not to do like this.
This requires defining 2 set of init calls, one for normal and one for charger init call.
We do not want to define separate init calls for charger.
We just want to take a decision during compile time to determine which initcalls should be used during charger mode.

Thus we need compile time comparison in macro which helps us in determining whether _this__ init call should be added in charger.init section or not.
Thus we can do as follows:-
------------------------------------------------------------------------------------------------------------------------------------
#define __define_initcall(level,fn,id)              static initcall_t __initcall_##fn##id __used __attribute__ ((__section__(".initcall" level ".init"))) = fn  \
                                                                #ifdef CHARGER_MODE  \
                                                                static initcall_t __charger_initcall_##fn##id __used __attribute__ ((__section__(".charger.initcall" level ".init"))) = fn  \
                                                                #endif
 
#define device_initcall(fn)      __define_initcall("6", fn, 6, 1)
#define __initcall(fn)          device_initcall(fn)
#define module_init(x)          __initcall(x);
#define early_initcall(fn)      module_init(fn)
------------------------------------------------------------------------------------------------------------------------------------

Basically we need something like:

#define     __define_initcall(....)                \
                                                             /* polupate init section */ \
                                                             #ifdef CHARGER_MODE  \
                                                             /* polupate charger.init section also */  \
                                                             #elif  ANOTHER_MODE  \
                                                             /* polupate another.init section also */  \
                                                             #elif ....
                                                             .............
                                                             .............
                                                             #endif

Is it possible to do "#if or #ifdef" inside "#define" ?????

Basically, we need to populate each.init section based on some compile time condition.
How can we do that????


Thanks,
Pintu
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