Including file in a makefile

[Innovator]

hello,
i want to include Af_unix.h(include/net/af_unix.h) file in my sche,h file of linux. but when I compile the kernel it gives me error Undefined reference to af_unix.h. Similar is the case when i include sys/types.h and unistd.h
I have also included the proper directory i mean for unistd.h i write
#include<linux/unistd.h>
Also i have properly included all the other files.
Can anyone please help me out why I am getting this error for all the files I am trying to include.
may be I need to make changes in the Makefile of the kernel
Please tell me out what are the required changes to be made.

[Rubberman]

This is in your kernel source, right? If so, it should be like this (assuming 'include' refers to the default include directory):

#include <net/af_unix.h>

If you need the ABSOLUTE path, then do this:

#include "/absolute-path-to-include/net/af_unix.h"

Note the difference between angle brackets in the first example, and double-quotes in the second. While not always important, in some cases this can be critical, though I won't explain the differences at this point.

[Innovator]

This is in your kernel source, right? If so, it should be like this (assuming 'include' refers to the default include directory):

#include <net/af_unix.h>

If you need the ABSOLUTE path, then do this:

#include "/absolute-path-to-include/net/af_unix.h"

Note the difference between angle brackets in the first example, and double-quotes in the second. While not always important, in some cases this can be critical, though I won't explain the differences at this point.

As you said i have included the socket.h file using its absolute path
But socket.h include a file named features.h
so when I compile my kernel module it gives me error : /usr/include/sys/socket.h: No such file or directory
same error is given for all the files which are included in socket.h
I think we should make changes in the makefile of the kernel module
(I am writing my own kernel module)

[Rubberman]

Ok. You need to add to the beginning of your CFLAGS make variable the flag "-I path-to-kernel-include-dir" where path-to-kernel-include-dir is usually something like "../../include" (assuming that the kernel include directory is 2 levels above your module build directory), otherwise it will likely be set to the default /usr/include path, which is where it would look to resolve those files. The error you quote about "/usr/include/sys/socket.h: No such file or directory" is the proof of that.