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>

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,