Simply added explanation from Al Viro in the following mail:
http://lkml.indiana.edu/hypermail/linux/kernel/0802.2/3164.html

Cc: Al Viro <viro@ftp.linux.org.uk>
Cc:  Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Documentation/sparse.txt tells to use:

    make C=2 CHECKFLAGS="-D__CHECK_ENDIAN__"

However, this still doesn't enable endian checks. The correct syntax is:

    make C=2 CF="-D__CHECK_ENDIAN__"

This documentation bug was introduced by the following commit:

    commit 1c7bafe7
    Author: Robert P. J. Day <rpjday@mindspring.com>
    Date:   Wed Sep 13 07:57:50 2006 -0400

	kbuild: clarify "make C=" build option

	Clarify the use of "make C=" in the top-level Makefile, and fix a
	typo in the Documentation file.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

This `typo' was not a typo, as `CF' had been introduced much earlier, by:

    commit 7b49bb9a
    Author: viro@ZenIV.linux.org.uk <viro@ZenIV.linux.org.uk>
    Date:   Fri Sep 9 21:14:35 2005 +0100

	[PATCH] kbuild: CF=<arguments> passes arguments to sparse

	Allows to add to sparse arguments without mutilating makefiles - just
	pass CF=<arguments> and they will be added to CHECKFLAGS.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NGeert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

 - point to the sparse webpage
 - use git:// instead of rsync://
Signed-off-by: NDave Jones <davej@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Clarify the use of "make C=" in the top-level Makefile, and fix a
typo in the Documentation file.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Update the sparse documentation to omit the -Wbitwise flag example (as it
is now passed by default), and document the kernel defines to enable
endianness checking.
Signed-off-by: NBob Copeland <me@bobcopeland.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NHarald Welte <laforge@netfilter.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The URL for Documentation/sparse is wrong now that it is in git.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!