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-rw-r--r--Documentation/kbuild/makefiles.txt66
1 files changed, 41 insertions, 25 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 37b525d329ae..b9f7ca4e62ae 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -44,10 +44,12 @@ 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 generic-y
--- 7.4 generated-y
+ --- 7.5 mandatory-y
+ --- 7.6 subdir-y
=== 8 Kbuild Variables
=== 9 Makefile language
@@ -1235,7 +1237,7 @@ 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
@@ -1262,37 +1264,30 @@ 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/asm/ and arch/<arch>/include/generated/uapi/asm/
+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 generic-y
@@ -1334,6 +1329,27 @@ 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.
+
+ --- 7.6 subdir-y
+
+ subdir-y may be used to specify a subdirectory to be exported.
+
+ Example:
+ #arch/cris/include/uapi/asm/Kbuild
+ subdir-y += ../arch-v10/arch/
+ subdir-y += ../arch-v32/arch/
+
+ The convention is to list one subdir per line and
+ preferably in alphabetic order.
+
=== 8 Kbuild Variables
The top Makefile exports the following variables: