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-rw-r--r--Documentation/kbuild/modules.txt40
1 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt
index 1c0db652b366..7e77f93634ea 100644
--- a/Documentation/kbuild/modules.txt
+++ b/Documentation/kbuild/modules.txt
@@ -18,6 +18,7 @@ In this document you will find information about:
18 === 5. Include files 18 === 5. Include files
19 --- 5.1 How to include files from the kernel include dir 19 --- 5.1 How to include files from the kernel include dir
20 --- 5.2 External modules using an include/ dir 20 --- 5.2 External modules using an include/ dir
21 --- 5.3 External modules using several directories
21 === 6. Module installation 22 === 6. Module installation
22 --- 6.1 INSTALL_MOD_PATH 23 --- 6.1 INSTALL_MOD_PATH
23 --- 6.2 INSTALL_MOD_DIR 24 --- 6.2 INSTALL_MOD_DIR
@@ -344,6 +345,45 @@ directory and therefore needs to deal with this in their kbuild file.
344 Note that in the assignment there is no space between -I and the path. 345 Note that in the assignment there is no space between -I and the path.
345 This is a kbuild limitation: there must be no space present. 346 This is a kbuild limitation: there must be no space present.
346 347
348--- 5.3 External modules using several directories
349
350 If an external module does not follow the usual kernel style but
351 decide to spread files over several directories then kbuild can
352 support this too.
353
354 Consider the following example:
355
356 |
357 +- src/complex_main.c
358 | +- hal/hardwareif.c
359 | +- hal/include/hardwareif.h
360 +- include/complex.h
361
362 To build a single module named complex.ko we then need the following
363 kbuild file:
364
365 Kbuild:
366 obj-m := complex.o
367 complex-y := src/complex_main.o
368 complex-y += src/hal/hardwareif.o
369
370 EXTRA_CFLAGS := -I$(src)/include
371 EXTRA_CFLAGS += -I$(src)src/hal/include
372
373
374 kbuild knows how to handle .o files located in another directory -
375 although this is NOT reccommended practice. The syntax is to specify
376 the directory relative to the directory where the Kbuild file is
377 located.
378
379 To find the .h files we have to explicitly tell kbuild where to look
380 for the .h files. When kbuild executes current directory is always
381 the root of the kernel tree (argument to -C) and therefore we have to
382 tell kbuild how to find the .h files using absolute paths.
383 $(src) will specify the absolute path to the directory where the
384 Kbuild file are located when being build as an external module.
385 Therefore -I$(src)/ is used to point out the directory of the Kbuild
386 file and any additional path are just appended.
347 387
348=== 6. Module installation 388=== 6. Module installation
349 389