Add .editorconfig file for basic formatting

EditorConfig is a specification to define the most basic code formatting
stuff, and it's supported by many editors and IDEs, either directly or
via plugins, including VSCode/VSCodium, Vim, emacs and more.

It allows to define formatting style related to indentation, charset,
end of lines and trailing whitespaces. It also allows to apply different
formats for different files based on wildcards, so for example it is
possible to apply different configs to *.{c,h}, *.py and *.rs.

In linux project, defining a .editorconfig might help to those people
that work on different projects with different indentation styles, so
they cannot define a global style. Now they will directly see the
correct indentation on every fresh clone of the project.

See https://editorconfig.org

Co-developed-by: Danny Lin <danny@kdrag0n.dev>
Signed-off-by: Danny Lin <danny@kdrag0n.dev>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Acked-by: Mickaël Salaün <mic@digikod.net>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Tested-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

doc: use KCFLAGS instead of EXTRA_CFLAGS to pass flags from command line

You should use KCFLAGS to pass additional compiler flags from the
command line. Using EXTRA_CFLAGS is wrong.

EXTRA_CFLAGS is supposed to specify flags applied only to the current
Makefile (and now deprecated in favor of ccflags-y).

It is still used in arch/mips/kvm/Makefile (and possibly in external
modules too). Passing EXTRA_CFLAGS from the command line overwrites
it and breaks the build.

I also fixed drivers/gpu/drm/tilcdc/Makefile because commit 816175dd1fd7
("drivers/gpu/drm/tilcdc: Makefile, only -Werror when no -W* in
EXTRA_CFLAGS") was based on the same misunderstanding.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Federico Vaga <federico.vaga@vaga.pv.it>
Link: https://lore.kernel.org/r/20210221152524.197693-1-masahiroy@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: remove mention of ENABLE_MUST_CHECK

We removed ENABLE_MUST_CHECK in 196793946264 ("Compiler Attributes:
remove CONFIG_ENABLE_MUST_CHECK"), so let's remove docs' mentions.

At the same time, fix the outdated text related to
ENABLE_WARN_DEPRECATED that wasn't removed in 3337d5cfe5e08
("configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED").

Finally, reflow the paragraph.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20210105055815.GA5173@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Replace HTTP links with HTTPS ones: Documentation/process

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
If not .svg:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lore.kernel.org/r/20200621133630.46435-1-grandmaster@al2klimov.de
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: fault-injection: convert docs to ReST and rename to *.rst

The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED

This Kconfig option was removed during v4.19 development in commit
771c035372a0 ("deprecate the '__deprecated' attribute warnings entirely
and for good") so there's no point to keep it in defconfigs any longer.

FWIW defconfigs were patched with:
--------------------------->8----------------------
find . -name *_defconfig -exec sed -i '/CONFIG_ENABLE_WARN_DEPRECATED/d' {} \;
--------------------------->8----------------------

Link: http://lkml.kernel.org/r/20190128152434.41969-1-abrodkin@synopsys.com
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

doc:process: add links where missing

Some documents are refering to others without links. With this
patch I add those missing links.

This patch affects only documents under process/ and labels where
necessary.

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

clang-format: add configuration file

clang-format is a tool to format C/C++/... code according to a set of
rules and heuristics. Like most tools, it is not perfect nor covers
every single case, but it is good enough to be helpful.

In particular, it is useful for quickly re-formatting blocks of code
automatically, for reviewing full files in order to spot coding style
mistakes, typos and possible improvements. It is also handy for sorting
``#includes``, for aligning variables and macros, for reflowing text and
other similar tasks. It also serves as a teaching tool/guide for
newcomers.

The tool itself has been already included in the repositories of popular
Linux distributions for a long time. The rules in this file are
intended for clang-format >= 4, which is easily available in most
distributions.

This commit adds the configuration file that contains the rules that the
tool uses to know how to format the code according to the kernel coding
style. This gives us several advantages:

* clang-format works out of the box with reasonable defaults;
avoiding that everyone has to re-do the configuration.

* Everyone agrees (eventually) on what is the most useful default
configuration for most of the kernel.

* If it becomes commonplace among kernel developers, clang-format
may feel compelled to support us better. They already recognize
the Linux kernel and its style in their documentation and in one
of the style sub-options.

Some of clang-format's features relevant for the kernel are:

* Uses clang's tooling support behind the scenes to parse and rewrite
the code. It is not based on ad-hoc regexps.

* Supports reasonably well the Linux kernel coding style.

* Fast enough to be used at the press of a key.

* There are already integrations (either built-in or third-party)
for many common editors used by kernel developers (e.g. vim,
emacs, Sublime, Atom...) that allow you to format an entire file
or, more usefully, just your selection.

* Able to parse unified diffs -- you can, for instance, reformat
only the lines changed by a git commit.

* Able to reflow text comments as well.

* Widely supported and used by hundreds of developers in highly
complex projects and organizations (e.g. the LLVM project itself,
Chromium, WebKit, Google, Mozilla...). Therefore, it will be
supported for a long time.

See more information about the tool at:

https://clang.llvm.org/docs/ClangFormat.html
https://clang.llvm.org/docs/ClangFormatStyleOptions.html

Link: http://lkml.kernel.org/r/20180318171632.qfkemw3mwbcukth6@gmail.com
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation: fix ref to coccinelle content

Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: process/4.Coding.rst: Fix a couple of document refs

In Documentation/process/4.Coding.rst there were a couple of paragraphs
that spilled over the 80 character line length. This was likely caused
when the document was converted to reStructuredText. Re-flow the
paragraphs and make the document references proper reStructuredText
:ref: links.

This also adds the appropriate reStructuredText file heading to
kernel-parameters.rst as referenced by the kernel-parameters link in
this patch.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs-rst: doc-guide: split the kernel-documentation.rst contents

Having the kernel-documentation at the topmost level doesn't
allow generating a separate PDF file for it. Also, makes harder
to add extra contents. So, place it on a sub-dir.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: fix locations of several documents that got moved

The previous patch renamed several files that are cross-referenced
along the Kernel documentation. Adjust the links to point to
the right places.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

docs: rename development-process/ to process/

As we'll type this a lot, after adding CodingStyle & friends,
let's rename the directory name to a shorter one.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>