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>

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 71c602d..f29dca3 100644 (file)
--- 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,