Use Symbols exported from other modules in the Linux driver

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Author: yuanlulu

Http://blog.csdn.net/yuanlulu

No copyright, but please keep this statement for reprinting
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I wrote a driver. It took a long time to get it done because it was dependent on the symbol exported by another module. Let's summarize my practices.

For ease of expression, I call the depended module Module B, and my own module is module.

 

Step 1:

Export the symbols to be used in the dependent Module B, such:

Int cat9555_state_get_indium (void)

{

................

}

Export_symbol (cat9555_state_get_indium );

 

Step 2:

Compile Module B, generate the module. symvers file under the current directory, and copy it to the directory of module.

Open Module. symvers and you will see the following content:

0x3c1007e5 cat9555_add_opt_addr/home/project/meterread/gpio export_symbol
0x20473c2b cat9555_state_get_indium/home/project/meterread/gpio export_symbol
0x3cc81287 cat9555_del_opt_addr/home/project/meterread/gpio export_symbol
0x68be5229 cat9555_release_addr/home/project/meterread/gpio export_symbol
0x743cae4d cat9555_state_as_gpo/home/project/meterread/gpio export_symbol
0x9c89640e cat9555_state_as_gpi/home/project/meterread/gpio export_symbol
0x977f0740 cat9555_open_addr/home/project/meterread/gpio export_symbol
0xf9713bbb cat9555_state_get_outp/home/project/meterread/gpio export_symbol
0x28d7d46f cat9555_state_set_outp/home/project/meterread/gpio export_symbol
This is the file that records the exported symbols.

Step 3:

Reference the exported symbol in the file of module.

Extern
Cat9555_state_get_indium (void); // declare that the referenced symbol is an external variable.

Int F (){

................

Cat9555_state_get_indium (); // reference the exported symbol here

................

}

Compile module.

If I do not have step 2, the following error occurs when I insert module A (the symbol cannot be found ):

Gwsiodrv: No symbol version for cat9555_state_get_indium
Gwsiodrv: Unknown symbol cat9555_state_get_indium
Gwsiodrv: No symbol version for cat9555_state_as_gpi
Gwsiodrv: Unknown symbol cat9555_state_as_gpi
Insmod: cannot insert 'gwsiodrv. Ko ': Unknown symbol in Module

 

However, some people do not need to use step 2 to guess that it is related to the compiler.