Re: building modules out of tree: how the header include paths work?

["Wang Yu" <wangyuict@xxxxxxxxx>]

On Wed, Dec 17, 2008 at 7:55 AM, Luis Henriques <henrix@xxxxxxx> wrote:

Hi,

On Tue, Dec 16, 2008 at 12:18:55PM -0500, Robert P. J. Day wrote:
>
>   i don't have access to a test system at the moment, so i'll
> embarrass myself by just asking:
>
>   when i'm writing a loadable module to be built out-of-tree, how do i
> properly configure the header file search path so i can include
> locally-written header files in my module?
>
>   say i have a module source file that needs to include the relative
> header file "../include/header.h".  i'm fairly sure i can just write:
>
>   #include "../include/header.h"
>
> and that will work with no additional configuration.  (this suggests
> that the kernel module build process automatically adds the source
> directory to its header file search path, correct?  otherwise, the
> above couldn't possibly work.)
>
>   but what if i want to just say:
>
>   #include "header.h"
>
> what's the proper way to invoke the kernel source tree Makefile to add
> the header file directory to the header file search path?  thanks.  i
> realize this is a simple question, i just don't have access to my work
> system at the moment to check it myself.

I believe the standard (recommended) way of doing this is using the EXTRA_CFLAGS
variable in your makefile.  Adding:

 EXTRA_CFLAGS := -I../include

should be enough for your code to work.

Take a look at Documentation/kbuild/modules.txt file ;)

   Yes, it is the standard:
    EXTRA_CFLAGS += -I../include
   and add ${ EXTRA_CFLAGS} to the gcc command~

--
Luis Henriques

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National Research Center for Intelligent Computing Systems
Institute of Computing Technology, Chinese Academy of Sciences