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authorMatt Mooney <mfm@muteddisk.com>2010-08-05 11:23:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-05 13:21:23 -0700
commit4f8272802739f5c6ce6b0a548810a181d2f1b652 (patch)
tree69c257ac7ad3be55414ab36f2ec318d942eecf2b /Documentation/kbuild/makefiles.txt
parentDocumentation/vm: fix spelling in page-types.c (diff)
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Documentation: update kbuild loadable modules goals & examples
Update section 3.3 Loadable module goals - obj-m, from $(<module_name>-objs) to $(<module_name>-y) for easier addition of conditional objects to the module. The examples are also updated to reflect the current state of each Makefile used. Signed-off-by: matt mooney <mfm@muteddisk.com> Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/kbuild/makefiles.txt')
-rw-r--r--Documentation/kbuild/makefiles.txt37
1 files changed, 19 insertions, 18 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 71c602d61680..f29dca374aa2 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -187,34 +187,35 @@ more details, with real examples.
Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
If a kernel module is built from several source files, you specify
- that you want to build a module in the same way as above.
-
- Kbuild needs to know which the parts that you want to build your
- module from, so you have to tell it by setting an
- $(<module_name>-objs) variable.
+ that you want to build a module in the same way as above; however,
+ kbuild needs to know which object files you want to build your
+ module from, so you have to tell it by setting a $(<module_name>-y)
+ variable.
Example:
#drivers/isdn/i4l/Makefile
- obj-$(CONFIG_ISDN) += isdn.o
- isdn-objs := isdn_net_lib.o isdn_v110.o isdn_common.o
+ obj-$(CONFIG_ISDN_I4L) += isdn.o
+ isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
In this example, the module name will be isdn.o. Kbuild will
- compile the objects listed in $(isdn-objs) and then run
+ compile the objects listed in $(isdn-y) and then run
"$(LD) -r" on the list of these files to generate isdn.o.
- Kbuild recognises objects used for composite objects by the suffix
- -objs, and the suffix -y. This allows the Makefiles to use
- the value of a CONFIG_ symbol to determine if an object is part
- of a composite object.
+ Due to kbuild recognizing $(<module_name>-y) for composite objects,
+ you can use the value of a CONFIG_ symbol to optionally include an
+ object file as part of a composite object.
Example:
#fs/ext2/Makefile
- obj-$(CONFIG_EXT2_FS) += ext2.o
- ext2-y := balloc.o bitmap.o
- ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
-
- In this example, xattr.o is only part of the composite object
- ext2.o if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'.
+ obj-$(CONFIG_EXT2_FS) += ext2.o
+ ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
+ namei.o super.o symlink.o
+ ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
+ xattr_trusted.o
+
+ In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
+ part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)
+ evaluates to 'y'.
Note: Of course, when you are building objects into the kernel,
the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,