Re: EXPORT_SYMBOL Vs extern?

[Li Zefan]

pradeep singh wrote:
 Hi All,
 
 A Quick but perhaps dumbass query,
 
 1. int function_A(...)
 {
  ...;
 }
 
 2. int function_B(...)
 {
  ...;
 }
 EXPORT_SYMBOL(function_B);
 
 Okay i understand I should use the EXPORT_SYMBOL way if i want
 function_B to be used by rest of the kernel.
 

Functions and variables which are exported through EXPORT_SYMBOL is
for kernel module code.

 Now I have a doubt -
 
 Is it a compulsion for a function which need to be used in any other
 source file, exported through EXPORT_SYMBOL only?
 Does this means all the places in kernel(and there are loads of them),
 where a function is non-static and is used in other source files
 should actually be using EXPORT_SYMBOL?
 
 Thanks,
  ~Pradeep


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RE: EXPORT_SYMBOL Vs extern?

[Rajat Jain]

Hi,

 
 Is it a compulsion for a function which need to be used in any other
 source file, exported through EXPORT_SYMBOL only? 
 Does this means all the places in kernel(and there are loads of
 them), where a function is non-static and is used in other source
 files should actually be using EXPORT_SYMBOL?  
 

EXPORT_SYMBOL is mandatory if you want to use a kernel defined function
in a module (or vice versa), or a module defined function in a different
module. 

You can use a non-static function (defined in say A.obj) in a different
obj file (defined in say B.obj) provide that both the objs either belong
to the same module, or are linked in the kernel at the compile time.

Thanks,

Rajat

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RE: EXPORT_SYMBOL Vs extern?

[Anirban Sinha]

EXPORT_SYMBOL macro creates a new kernel symbol entry (address of the symbol, 
symbol) based on the value you specify and puts it in a special section of the 
kernel image, in __ksymtab section. When modules are loaded dynamically, the 
loader resolves the symbols during run time by parsing the entries of this 
section.

Extern can be used for non-static functions that are statically linked during 
compile time.

HTH,

Ani


-Original Message-
From: [EMAIL PROTECTED] [mailto:kernelnewbies-
[EMAIL PROTECTED] On Behalf Of pradeep singh
Sent: Sunday, May 04, 2008 10:38 PM
To: Kernel List
Subject: EXPORT_SYMBOL Vs extern?

Hi All,

A Quick but perhaps dumbass query,

1. int function_A(...)
{
 ...;
}

2. int function_B(...)
{
 ...;
}
EXPORT_SYMBOL(function_B);

Okay i understand I should use the EXPORT_SYMBOL way if i want
function_B to be used by rest of the kernel.

Now I have a doubt -

Is it a compulsion for a function which need to be used in any other
source file, exported through EXPORT_SYMBOL only?
Does this means all the places in kernel(and there are loads of them),
where a function is non-static and is used in other source files
should actually be using EXPORT_SYMBOL?

Thanks,
 ~Pradeep
--
play the game

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