Merge tag 'docs-4.16' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "Documentation updates for 4.16.

  New stuff includes refcount_t documentation, errseq documentation,
  kernel-doc support for nested structure definitions, the removal of
  lots of crufty kernel-doc support for unused formats, SPDX tag
  documentation, the beginnings of a manual for subsystem maintainers,
  and lots of fixes and updates.

  As usual, some of the changesets reach outside of Documentation/ to
  effect kerneldoc comment fixes. It also adds the new LICENSES
  directory, of which Thomas promises I do not need to be the
  maintainer"

* tag 'docs-4.16' of git://git.lwn.net/linux: (65 commits)
  linux-next: docs-rst: Fix typos in kfigure.py
  linux-next: DOC: HWPOISON: Fix path to debugfs in hwpoison.txt
  Documentation: Fix misconversion of #if
  docs: add index entry for networking/msg_zerocopy
  Documentation: security/credentials.rst: explain need to sort group_list
  LICENSES: Add MPL-1.1 license
  LICENSES: Add the GPL 1.0 license
  LICENSES: Add Linux syscall note exception
  LICENSES: Add the MIT license
  LICENSES: Add the BSD-3-clause "Clear" license
  LICENSES: Add the BSD 3-clause "New" or "Revised" License
  LICENSES: Add the BSD 2-clause "Simplified" license
  LICENSES: Add the LGPL-2.1 license
  LICENSES: Add the LGPL 2.0 license
  LICENSES: Add the GPL 2.0 license
  Documentation: Add license-rules.rst to describe how to properly identify file licenses
  scripts: kernel_doc: better handle show warnings logic
  fs/*/Kconfig: drop links to 404-compliant http://acl.bestbits.at
  doc: md: Fix a file name to md-fault.c in fault-injection.txt
  errseq: Add to documentation tree
  ...

3 files changed, 376 insertions, 1 deletions

diff --git a/Documentation/process/kernel-enforcement-statement.rst b/Documentation/process/kernel-enforcement-statement.rst
index bfa6a78103d8..6816c12d6956 100644
--- a/Documentation/process/kernel-enforcement-statement.rst
+++ b/Documentation/process/kernel-enforcement-statement.rst
@@ -68,6 +68,7 @@ we might work for today, have in the past, or will in the future.
   - Paul Burton
   - Javier Martinez Canillas
   - Rob Clark
+  - Kees Cook (Google)
   - Jonathan Corbet
   - Dennis Dalessandro
   - Vivien Didelot (Savoir-faire Linux)
@@ -137,6 +138,7 @@ we might work for today, have in the past, or will in the future.
   - Anna Schumaker
   - Jes Sorensen
   - K.Y. Srinivasan
+  - David Sterba (SUSE)
   - Heiko Stuebner
   - Jiri Kosina (SUSE)
   - Willy Tarreau
@@ -144,6 +146,7 @@ we might work for today, have in the past, or will in the future.
   - Linus Torvalds
   - Thierry Reding
   - Rik van Riel
+  - Luis R. Rodriguez
   - Geert Uytterhoeven (Glider bvba)
   - Eduardo Valentin (Amazon.com)
   - Daniel Vetter
diff --git a/Documentation/process/license-rules.rst b/Documentation/process/license-rules.rst
new file mode 100644
index 000000000000..408f77dc6157
--- /dev/null
+++ b/Documentation/process/license-rules.rst
@@ -0,0 +1,370 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Linux kernel licensing rules
+============================
+
+The Linux Kernel is provided under the terms of the GNU General Public
+License version 2 only (GPL-2.0), as published by the Free Software
+Foundation, and provided in the COPYING file.  This documentation file is
+not meant to replace the COPYING file, but provides a description of how
+each source file should be annotated to make the licensing it is governed
+under clear and unambiguous.
+
+The license in the COPYING file applies to the kernel source as a whole,
+though individual source files can have a different license which is
+required to be compatible with the GPL-2.0::
+
+    GPL-1.0+  :  GNU General Public License v1.0 or later
+    GPL-2.0+  :  GNU General Public License v2.0 or later
+    LGPL-2.0  :  GNU Library General Public License v2 only
+    LGPL-2.0+ :  GNU Library General Public License v2 or later
+    LGPL-2.1  :  GNU Lesser General Public License v2.1 only
+    LGPL-2.1+ :  GNU Lesser General Public License v2.1 or later
+
+Aside from that, individual files can be provided under a dual license,
+e.g. one of the compatible GPL variants and alternatively under a
+permissive license like BSD, MIT etc.
+
+The User-space API (UAPI) header files, which describe the interface of
+user-space programs to the kernel are a special case.  According to the
+note in the kernel COPYING file, the syscall interface is a clear boundary,
+which does not extend the GPL requirements to any software which uses it to
+communicate with the kernel.  Because the UAPI headers must be includable
+into any source files which create an executable running on the Linux
+kernel, the exception must be documented by a special license expression.
+
+The common way of expressing the license of a source file is to add the
+matching boilerplate text into the top comment of the file.  Due to
+formatting, typos etc. these "boilerplates" are hard to validate for
+tools which are used in the context of license compliance.
+
+An alternative to boilerplate text is the use of Software Package Data
+Exchange (SPDX) license identifiers in each source file.  SPDX license
+identifiers are machine parsable and precise shorthands for the license
+under which the content of the file is contributed.  SPDX license
+identifiers are managed by the SPDX Workgroup at the Linux Foundation and
+have been agreed on by partners throughout the industry, tool vendors, and
+legal teams.  For further information see https://spdx.org/
+
+The Linux kernel requires the precise SPDX identifier in all source files.
+The valid identifiers used in the kernel are explained in the section
+`License identifiers`_ and have been retrieved from the official SPDX
+license list at https://spdx.org/licenses/ along with the license texts.
+
+License identifier syntax
+-------------------------
+
+1. Placement:
+
+   The SPDX license identifier in kernel files shall be added at the first
+   possible line in a file which can contain a comment.  For the majority
+   or files this is the first line, except for scripts which require the
+   '#!PATH_TO_INTERPRETER' in the first line.  For those scripts the SPDX
+   identifier goes into the second line.
+
+|
+
+2. Style:
+
+   The SPDX license identifier is added in form of a comment.  The comment
+   style depends on the file type::
+
+      C source:	// SPDX-License-Identifier: <SPDX License Expression>
+      C header:	/* SPDX-License-Identifier: <SPDX License Expression> */
+      ASM:	/* SPDX-License-Identifier: <SPDX License Expression> */
+      scripts:	# SPDX-License-Identifier: <SPDX License Expression>
+      .rst:	.. SPDX-License-Identifier: <SPDX License Expression>
+      .dts{i}:	// SPDX-License-Identifier: <SPDX License Expression>
+
+   If a specific tool cannot handle the standard comment style, then the
+   appropriate comment mechanism which the tool accepts shall be used. This
+   is the reason for having the "/\* \*/" style comment in C header
+   files. There was build breakage observed with generated .lds files where
+   'ld' failed to parse the C++ comment. This has been fixed by now, but
+   there are still older assembler tools which cannot handle C++ style
+   comments.
+
+|
+
+3. Syntax:
+
+   A <SPDX License Expression> is either an SPDX short form license
+   identifier found on the SPDX License List, or the combination of two
+   SPDX short form license identifiers separated by "WITH" when a license
+   exception applies. When multiple licenses apply, an expression consists
+   of keywords "AND", "OR" separating sub-expressions and surrounded by
+   "(", ")" .
+
+   License identifiers for licenses like [L]GPL with the 'or later' option
+   are constructed by using a "+" for indicating the 'or later' option.::
+
+      // SPDX-License-Identifier: GPL-2.0+
+      // SPDX-License-Identifier: LGPL-2.1+
+
+   WITH should be used when there is a modifier to a license needed.
+   For example, the linux kernel UAPI files use the expression::
+
+      // SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
+      // SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note
+
+   Other examples using WITH exceptions found in the kernel are::
+
+      // SPDX-License-Identifier: GPL-2.0 WITH mif-exception
+      // SPDX-License-Identifier: GPL-2.0+ WITH GCC-exception-2.0
+
+   Exceptions can only be used with particular License identifiers. The
+   valid License identifiers are listed in the tags of the exception text
+   file. For details see the point `Exceptions`_ in the chapter `License
+   identifiers`_.
+
+   OR should be used if the file is dual licensed and only one license is
+   to be selected.  For example, some dtsi files are available under dual
+   licenses::
+
+      // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+
+   Examples from the kernel for license expressions in dual licensed files::
+
+      // SPDX-License-Identifier: GPL-2.0 OR MIT
+      // SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+      // SPDX-License-Identifier: GPL-2.0 OR Apache-2.0
+      // SPDX-License-Identifier: GPL-2.0 OR MPL-1.1
+      // SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) OR MIT
+      // SPDX-License-Identifier: GPL-1.0+ OR BSD-3-Clause OR OpenSSL
+
+   AND should be used if the file has multiple licenses whose terms all
+   apply to use the file. For example, if code is inherited from another
+   project and permission has been given to put it in the kernel, but the
+   original license terms need to remain in effect::
+
+      // SPDX-License-Identifier: (GPL-2.0 WITH Linux-syscall-note) AND MIT
+
+   Another other example where both sets of license terms need to be
+   adhered to is::
+
+      // SPDX-License-Identifier: GPL-1.0+ AND LGPL-2.1+
+
+License identifiers
+-------------------
+
+The licenses currently used, as well as the licenses for code added to the
+kernel, can be broken down into:
+
+1. _`Preferred licenses`:
+
+   Whenever possible these licenses should be used as they are known to be
+   fully compatible and widely used.  These licenses are available from the
+   directory::
+
+      LICENSES/preferred/
+
+   in the kernel source tree.
+
+   The files in this directory contain the full license text and
+   `Metatags`_.  The file names are identical to the SPDX license
+   identifier which shall be used for the license in source files.
+
+   Examples::
+
+      LICENSES/preferred/GPL-2.0
+
+   Contains the GPL version 2 license text and the required metatags::
+
+      LICENSES/preferred/MIT
+
+   Contains the MIT license text and the required metatags
+
+   _`Metatags`:
+
+   The following meta tags must be available in a license file:
+
+   - Valid-License-Identifier:
+
+     One or more lines which declare which License Identifiers are valid
+     inside the project to reference this particular license text.  Usually
+     this is a single valid identifier, but e.g. for licenses with the 'or
+     later' options two identifiers are valid.
+
+   - SPDX-URL:
+
+     The URL of the SPDX page which contains additional information related
+     to the license.
+
+   - Usage-Guidance:
+
+     Freeform text for usage advice. The text must include correct examples
+     for the SPDX license identifiers as they should be put into source
+     files according to the `License identifier syntax`_ guidelines.
+
+   - License-Text:
+
+     All text after this tag is treated as the original license text
+
+   File format examples::
+
+      Valid-License-Identifier: GPL-2.0
+      Valid-License-Identifier: GPL-2.0+
+      SPDX-URL: https://spdx.org/licenses/GPL-2.0.html
+      Usage-Guide:
+        To use this license in source code, put one of the following SPDX
+	tag/value pairs into a comment according to the placement
+	guidelines in the licensing rules documentation.
+	For 'GNU General Public License (GPL) version 2 only' use:
+	  SPDX-License-Identifier: GPL-2.0
+	For 'GNU General Public License (GPL) version 2 or any later version' use:
+	  SPDX-License-Identifier: GPL-2.0+
+      License-Text:
+        Full license text
+
+   ::
+
+      SPDX-License-Identifier: MIT
+      SPDX-URL: https://spdx.org/licenses/MIT.html
+      Usage-Guide:
+	To use this license in source code, put the following SPDX
+	tag/value pair into a comment according to the placement
+	guidelines in the licensing rules documentation.
+	  SPDX-License-Identifier: MIT
+      License-Text:
+        Full license text
+
+|
+
+2. Not recommended licenses:
+
+   These licenses should only be used for existing code or for importing
+   code from a different project.  These licenses are available from the
+   directory::
+
+      LICENSES/other/
+
+   in the kernel source tree.
+
+   The files in this directory contain the full license text and
+   `Metatags`_.  The file names are identical to the SPDX license
+   identifier which shall be used for the license in source files.
+
+   Examples::
+
+      LICENSES/other/ISC
+
+   Contains the Internet Systems Consortium license text and the required
+   metatags::
+
+      LICENSES/other/ZLib
+
+   Contains the ZLIB license text and the required metatags.
+
+   Metatags:
+
+   The metatag requirements for 'other' licenses are identical to the
+   requirements of the `Preferred licenses`_.
+
+   File format example::
+
+      Valid-License-Identifier: ISC
+      SPDX-URL: https://spdx.org/licenses/ISC.html
+      Usage-Guide:
+        Usage of this license in the kernel for new code is discouraged
+	and it should solely be used for importing code from an already
+	existing project.
+        To use this license in source code, put the following SPDX
+	tag/value pair into a comment according to the placement
+	guidelines in the licensing rules documentation.
+	  SPDX-License-Identifier: ISC
+      License-Text:
+        Full license text
+
+|
+
+3. _`Exceptions`:
+
+   Some licenses can be amended with exceptions which grant certain rights
+   which the original license does not.  These exceptions are available
+   from the directory::
+
+      LICENSES/exceptions/
+
+   in the kernel source tree.  The files in this directory contain the full
+   exception text and the required `Exception Metatags`_.
+
+   Examples::
+
+      LICENSES/exceptions/Linux-syscall-note
+
+   Contains the Linux syscall exception as documented in the COPYING
+   file of the Linux kernel, which is used for UAPI header files.
+   e.g. /\* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note \*/::
+
+      LICENSES/exceptions/GCC-exception-2.0
+
+   Contains the GCC 'linking exception' which allows to link any binary
+   independent of its license against the compiled version of a file marked
+   with this exception. This is required for creating runnable executables
+   from source code which is not compatible with the GPL.
+
+   _`Exception Metatags`:
+
+   The following meta tags must be available in an exception file:
+
+   - SPDX-Exception-Identifier:
+
+     One exception identifier which can be used with SPDX license
+     identifiers.
+
+   - SPDX-URL:
+
+     The URL of the SPDX page which contains additional information related
+     to the exception.
+
+   - SPDX-Licenses:
+
+     A comma separated list of SPDX license identifiers for which the
+     exception can be used.
+
+   - Usage-Guidance:
+
+     Freeform text for usage advice. The text must be followed by correct
+     examples for the SPDX license identifiers as they should be put into
+     source files according to the `License identifier syntax`_ guidelines.
+
+   - Exception-Text:
+
+     All text after this tag is treated as the original exception text
+
+   File format examples::
+
+      SPDX-Exception-Identifier: Linux-syscall-note
+      SPDX-URL: https://spdx.org/licenses/Linux-syscall-note.html
+      SPDX-Licenses: GPL-2.0, GPL-2.0+, GPL-1.0+, LGPL-2.0, LGPL-2.0+, LGPL-2.1, LGPL-2.1+
+      Usage-Guidance:
+        This exception is used together with one of the above SPDX-Licenses
+	to mark user-space API (uapi) header files so they can be included
+	into non GPL compliant user-space application code.
+        To use this exception add it with the keyword WITH to one of the
+	identifiers in the SPDX-Licenses tag:
+	  SPDX-License-Identifier: <SPDX-License> WITH Linux-syscall-note
+      Exception-Text:
+        Full exception text
+
+   ::
+
+      SPDX-Exception-Identifier: GCC-exception-2.0
+      SPDX-URL: https://spdx.org/licenses/GCC-exception-2.0.html
+      SPDX-Licenses: GPL-2.0, GPL-2.0+
+      Usage-Guidance:
+        The "GCC Runtime Library exception 2.0" is used together with one
+	of the above SPDX-Licenses for code imported from the GCC runtime
+	library.
+        To use this exception add it with the keyword WITH to one of the
+	identifiers in the SPDX-Licenses tag:
+	  SPDX-License-Identifier: <SPDX-License> WITH GCC-exception-2.0
+      Exception-Text:
+        Full exception text
+
+
+All SPDX license identifiers and exceptions must have a corresponding file
+in the LICENSE subdirectories. This is required to allow tool
+verification (e.g. checkpatch.pl) and to have the licenses ready to read
+and extract right from the source, which is recommended by various FOSS
+organizations, e.g. the `FSFE REUSE initiative <https://reuse.software/>`_.
diff --git a/Documentation/process/submit-checklist.rst b/Documentation/process/submit-checklist.rst
index a0d9d34bfb6d..367353c54949 100644
--- a/Documentation/process/submit-checklist.rst
+++ b/Documentation/process/submit-checklist.rst
@@ -37,7 +37,9 @@ and elsewhere regarding submitting Linux kernel patches.
    You should be able to justify all violations that remain in
    your patch.
 
-6) Any new or modified ``CONFIG`` options don't muck up the config menu.
+6) Any new or modified ``CONFIG`` options do not muck up the config menu and
+   default to off unless they meet the exception criteria documented in
+   ``Documentation/kbuild/kconfig-language.txt`` Menu attributes: default value.
 
 7) All new ``Kconfig`` options have help text.