Merge tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild UAPI updates from Masahiro Yamada:
 "Improvement of headers_install by Nicolas Dichtel.

  It has been long since the introduction of uapi directories, but the
  de-coupling of exported headers has not been completed. Headers listed
  in header-y are exported whether they exist in uapi directories or
  not. His work fixes this inconsistency.

  All (and only) headers under uapi directories are now exported. The
  asm-generic wrappers are still exceptions, but this is a big step
  forward"

* tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  arch/include: remove empty Kbuild files
  uapi: export all arch specifics directories
  uapi: export all headers under uapi directories
  smc_diag.h: fix include from userland
  btrfs_tree.h: fix include from userland
  uapi: includes linux/types.h before exporting files
  Makefile.headersinst: remove destination-y option
  Makefile.headersinst: cleanup input files
  x86: stop exporting msr-index.h to userland
  nios2: put setup.h in uapi
  h8300: put bitsperlong.h in uapi

1 files changed, 31 insertions, 43 deletions

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 9b9c4797fc55..e18daca65ccd 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -44,11 +44,11 @@ This document describes the Linux kernel Makefiles.
 	   --- 6.11 Post-link pass
 
 	=== 7 Kbuild syntax for exported headers
-		--- 7.1 header-y
+		--- 7.1 no-export-headers
 		--- 7.2 genhdr-y
-		--- 7.3 destination-y
-		--- 7.4 generic-y
-		--- 7.5 generated-y
+		--- 7.3 generic-y
+		--- 7.4 generated-y
+		--- 7.5 mandatory-y
 
 	=== 8 Kbuild Variables
 	=== 9 Makefile language
@@ -1236,7 +1236,7 @@ When kbuild executes, the following steps are followed (roughly):
 	that may be shared between individual architectures.
 	The recommended approach how to use a generic header file is
 	to list the file in the Kbuild file.
-	See "7.4 generic-y" for further info on syntax etc.
+	See "7.3 generic-y" for further info on syntax etc.
 
 --- 6.11 Post-link pass
 
@@ -1263,53 +1263,32 @@ The pre-processing does:
 - drop include of compiler.h
 - drop all sections that are kernel internal (guarded by ifdef __KERNEL__)
 
-Each relevant directory contains a file name "Kbuild" which specifies the
-headers to be exported.
-See subsequent chapter for the syntax of the Kbuild file.
-
-	--- 7.1 header-y
-
-	header-y specifies header files to be exported.
-
-		Example:
-			#include/linux/Kbuild
-			header-y += usb/
-			header-y += aio_abi.h
+All headers under include/uapi/, include/generated/uapi/,
+arch/<arch>/include/uapi/ and arch/<arch>/include/generated/uapi/
+are exported.
 
-	The convention is to list one file per line and
-	preferably in alphabetic order.
+A Kbuild file may be defined under arch/<arch>/include/uapi/asm/ and
+arch/<arch>/include/asm/ to list asm files coming from asm-generic.
+See subsequent chapter for the syntax of the Kbuild file.
 
-	header-y also specifies which subdirectories to visit.
-	A subdirectory is identified by a trailing '/' which
-	can be seen in the example above for the usb subdirectory.
+	--- 7.1 no-export-headers
 
-	Subdirectories are visited before their parent directories.
+	no-export-headers is essentially used by include/uapi/linux/Kbuild to
+	avoid exporting specific headers (e.g. kvm.h) on architectures that do
+	not support it. It should be avoided as much as possible.
 
 	--- 7.2 genhdr-y
 
-	genhdr-y specifies generated files to be exported.
-	Generated files are special as they need to be looked
-	up in another directory when doing 'make O=...' builds.
+	genhdr-y specifies asm files to be generated.
 
 		Example:
-			#include/linux/Kbuild
-			genhdr-y += version.h
+			#arch/x86/include/uapi/asm/Kbuild
+			genhdr-y += unistd_32.h
+			genhdr-y += unistd_64.h
+			genhdr-y += unistd_x32.h
 
-	--- 7.3 destination-y
 
-	When an architecture has a set of exported headers that needs to be
-	exported to a different directory destination-y is used.
-	destination-y specifies the destination directory for all exported
-	headers in the file where it is present.
-
-		Example:
-			#arch/xtensa/platforms/s6105/include/platform/Kbuild
-			destination-y := include/linux
-
-	In the example above all exported headers in the Kbuild file
-	will be located in the directory "include/linux" when exported.
-
-	--- 7.4 generic-y
+	--- 7.3 generic-y
 
 	If an architecture uses a verbatim copy of a header from
 	include/asm-generic then this is listed in the file
@@ -1336,7 +1315,7 @@ See subsequent chapter for the syntax of the Kbuild file.
 		Example: termios.h
 			#include <asm-generic/termios.h>
 
-	--- 7.5 generated-y
+	--- 7.4 generated-y
 
 	If an architecture generates other header files alongside generic-y
 	wrappers, and not included in genhdr-y, then generated-y specifies
@@ -1349,6 +1328,15 @@ See subsequent chapter for the syntax of the Kbuild file.
 			#arch/x86/include/asm/Kbuild
 			generated-y += syscalls_32.h
 
+	--- 7.5 mandatory-y
+
+	mandatory-y is essentially used by include/uapi/asm-generic/Kbuild.asm
+	to define the minimun set of headers that must be exported in
+	include/asm.
+
+	The convention is to list one subdir per line and
+	preferably in alphabetic order.
+
 === 8 Kbuild Variables
 
 The top Makefile exports the following variables: