Commit:     451ad114c6d8c5d39fd41d886fe87179d012ac73
Parent:     1ee052253c780493fa8814c1fe83e87494ae694d
Author:     Rob Landley <[EMAIL PROTECTED]>
AuthorDate: Tue Oct 16 23:31:16 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Oct 17 08:43:05 2007 -0700

    Some documentation for "make headers_install".
    Signed-off-by: Rob Landley <[EMAIL PROTECTED]>
    Cc: David Woodhouse <[EMAIL PROTECTED]>
    Cc: Sam Ravnborg <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 Documentation/make/headers_install.txt |   46 ++++++++++++++++++++++++++++++++
 1 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/Documentation/make/headers_install.txt 
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+Exporting kernel headers for use by userspace
+The "make headers_install" command exports the kernel's header files in a
+form suitable for use by userspace programs.
+The linux kernel's exported header files describe the API for user space
+programs attempting to use kernel services.  These kernel header files are
+used by the system's C library (such as glibc or uClibc) to define available
+system calls, as well as constants and structures to be used with these
+system calls.  The C library's header files include the kernel header files
+from the "linux" subdirectory.  The system's libc headers are usually
+installed at the default location /usr/include and the kernel headers in
+subdirectories under that (most notably /usr/include/linux and
+Kernel headers are backwards compatible, but not forwards compatible.  This
+means that a program built against a C library using older kernel headers
+should run on a newer kernel (although it may not have access to new
+features), but a program built against newer kernel headers may not work on an
+older kernel.
+The "make headers_install" command can be run in the top level directory of the
+kernel source code (or using a standard out-of-tree build).  It takes two
+optional arguments:
+  make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include
+ARCH indicates which architecture to produce headers for, and defaults to the
+current architecture.  The linux/asm directory of the exported kernel headers
+is platform-specific, to see a complete list of supported architectures use
+the command:
+  ls -d include/asm-* | sed 's/.*-//'
+INSTALL_HDR_PATH indicates where to install the headers.  It defaults to
+The command "make headers_install_all" exports headers for all architectures
+simultaneously.  (This is mostly of interest to distribution maintainers,
+who create an architecture-independent tarball from the resulting include
+directory.)  Remember to provide the appropriate linux/asm directory via "mv"
+or "ln -s" before building a C library with headers exported this way.
+The kernel header export infrastructure is maintained by David Woodhouse
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