[PATCH] Documentation/CodingStyle: Use directory-local variables for emacs

[Bart Van Assche <bvanassche@acm.org>]

In emacs 23.1 support for directory-local variables was added (see also
https://lists.gnu.org/archive/html/info-gnu-emacs/2009-07/msg00000.html).
Simplify the settings in coding-style.rst by using that feature.
Additionally, do not inherit any settings from emacs' linux coding style
to minimize dependencies on the version of emacs that is being used.

I have verified with several large and nontrivial kernel source files
that the new settings format code according to what checkpatch expects.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Geyslan G. Bem <geyslan@gmail.com>
Cc: Tiago Natel de Moura <tiago4orion@gmail.com>
Cc: Alison Chaiken <alison@she-devel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Federico Vaga <federico.vaga@vaga.pv.it>
Cc: Li Yang <leo@zh-kernel.org>
---
 Documentation/process/coding-style.rst | 57 +++++++++++++++++---------
 1 file changed, 37 insertions(+), 20 deletions(-)

Changes compared to v1:
- Removed top-level .dir-locals.el file again and updated coding-style.rst instead.
- Restored the humourous paragraph about emacs.
- Left out Italian and Chinese translations.
 
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 277c113376a6..5013883aec8e 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -592,26 +592,43 @@ values.  To do the latter, you can stick the following in your .emacs file:
       (* (max steps 1)
          c-basic-offset)))
 
-  (add-hook 'c-mode-common-hook
-            (lambda ()
-              ;; Add kernel style
-              (c-add-style
-               "linux-tabs-only"
-               '("linux" (c-offsets-alist
-                          (arglist-cont-nonempty
-                           c-lineup-gcc-asm-reg
-                           c-lineup-arglist-tabs-only))))))
-
-  (add-hook 'c-mode-hook
-            (lambda ()
-              (let ((filename (buffer-file-name)))
-                ;; Enable kernel mode for the appropriate files
-                (when (and filename
-                           (string-match (expand-file-name "~/src/linux-trees")
-                                         filename))
-                  (setq indent-tabs-mode t)
-                  (setq show-trailing-whitespace t)
-                  (c-set-style "linux-tabs-only")))))
+  (dir-locals-set-class-variables
+   'linux-kernel
+   '((c-mode . (
+          (c-basic-offset . 8)
+          (c-label-minimum-indentation . 0)
+          (c-offsets-alist . (
+                  (arglist-close         . c-lineup-arglist-tabs-only)
+                  (arglist-cont-nonempty .
+		      (c-lineup-gcc-asm-reg c-lineup-arglist-tabs-only))
+                  (arglist-intro         . +)
+                  (brace-list-intro      . +)
+                  (c                     . c-lineup-C-comments)
+                  (case-label            . 0)
+                  (comment-intro         . c-lineup-comment)
+                  (cpp-define-intro      . +)
+                  (cpp-macro             . -1000)
+                  (cpp-macro-cont        . +)
+                  (defun-block-intro     . +)
+                  (else-clause           . 0)
+                  (func-decl-cont        . +)
+                  (inclass               . +)
+                  (inher-cont            . c-lineup-multi-inher)
+                  (knr-argdecl-intro     . 0)
+                  (label                 . -1000)
+                  (statement             . 0)
+                  (statement-block-intro . +)
+                  (statement-case-intro  . +)
+                  (statement-cont        . +)
+                  (substatement          . +)
+                  ))
+          (indent-tabs-mode . t)
+          (show-trailing-whitespace . t)
+          ))))
+
+  (dir-locals-set-directory-class
+   (expand-file-name "~/src/linux-trees")
+   'linux-kernel)
 
 This will make emacs go better with the kernel coding style for C
 files below ``~/src/linux-trees``.
-- 
2.20.1.97.g81188d93c3-goog