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><A
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>Modules Spanning Multiple Files</H1
><A
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><P
>Sometimes it makes sense to divide a kernel module between several source files. In this case, you need to:</P
><P
></P
><OL
TYPE="1"
><LI
><P
>In all the source files but one, add the line <B
CLASS="COMMAND"
>#define __NO_VERSION__</B
>. This is important
because <TT
CLASS="FILENAME"
>module.h</TT
> normally includes the definition of
<TT
CLASS="VARNAME"
>kernel_version</TT
>, a global variable with the kernel version the module is compiled for. If you need
<TT
CLASS="FILENAME"
>version.h</TT
>, you need to include it yourself, because <TT
CLASS="FILENAME"
>module.h</TT
> won't do it for you with <TT
CLASS="VARNAME"
>__NO_VERSION__</TT
>.</P
></LI
><LI
><P
>Compile all the source files as usual.</P
></LI
><LI
><P
>Combine all the object files into a single one. Under x86, use <B
CLASS="COMMAND"
>ld -m elf_i386 -r -o <module
name.o> <1st src file.o> <2nd src file.o></B
>.</P
></LI
></OL
><P
>The makefile will, once again, save us from having to get our hands dirty with compiling and linking the object files.</P
><P
>Here's an example of such a kernel module.</P
><A
NAME="AEN399"
></A
><DIV
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><A
NAME="AEN402"
></A
><P
><B
>Example 2-8. start.c</B
></P
><PRE
CLASS="PROGRAMLISTING"
>/*
* start.c - Illustration of multi filed modules
*/
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/module.h> /* Specifically, a module */
int init_module(void)
{
printk("Hello, world - this is the kernel speaking\n");
return 0;
}</PRE
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><P
>The next file:</P
><A
NAME="AEN407"
></A
><DIV
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><A
NAME="AEN410"
></A
><P
><B
>Example 2-9. stop.c</B
></P
><PRE
CLASS="PROGRAMLISTING"
>/*
* stop.c - Illustration of multi filed modules
*/
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/module.h> /* Specifically, a module */
void cleanup_module()
{
printk("<1>Short is the life of a kernel module\n");
}</PRE
></DIV
><P
>And finally, the makefile:</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN415"
></A
><P
><B
>Example 2-10. Makefile</B
></P
><PRE
CLASS="PROGRAMLISTING"
>obj-m += hello-1.o
obj-m += hello-2.o
obj-m += hello-3.o
obj-m += hello-4.o
obj-m += hello-5.o
obj-m += startstop.o
startstop-objs := start.o stop.o</PRE
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