diff options
| -rw-r--r-- | Documentation/kbuild/modules.txt | 40 |
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: === 5. Include files --- 5.1 How to include files from the kernel include dir --- 5.2 External modules using an include/ dir + --- 5.3 External modules using several directories === 6. Module installation --- 6.1 INSTALL_MOD_PATH --- 6.2 INSTALL_MOD_DIR @@ -344,6 +345,45 @@ directory and therefore needs to deal with this in their kbuild file. Note that in the assignment there is no space between -I and the path. This is a kbuild limitation: there must be no space present. +--- 5.3 External modules using several directories + + If an external module does not follow the usual kernel style but + decide to spread files over several directories then kbuild can + support this too. + + Consider the following example: + + | + +- src/complex_main.c + | +- hal/hardwareif.c + | +- hal/include/hardwareif.h + +- include/complex.h + + To build a single module named complex.ko we then need the following + kbuild file: + + Kbuild: + obj-m := complex.o + complex-y := src/complex_main.o + complex-y += src/hal/hardwareif.o + + EXTRA_CFLAGS := -I$(src)/include + EXTRA_CFLAGS += -I$(src)src/hal/include + + + kbuild knows how to handle .o files located in another directory - + although this is NOT reccommended practice. The syntax is to specify + the directory relative to the directory where the Kbuild file is + located. + + To find the .h files we have to explicitly tell kbuild where to look + for the .h files. When kbuild executes current directory is always + the root of the kernel tree (argument to -C) and therefore we have to + tell kbuild how to find the .h files using absolute paths. + $(src) will specify the absolute path to the directory where the + Kbuild file are located when being build as an external module. + Therefore -I$(src)/ is used to point out the directory of the Kbuild + file and any additional path are just appended. === 6. Module installation |