Date:	Tue, 16 Feb 2016 15:55:08 -0300
From:	"Geyslan G. Bem" <geyslan@...il.com>
To:	Jonathan Corbet <corbet@....net>
Cc:	"Geyslan G. Bem" <geyslan@...il.com>, linux-doc@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, linux-usb@...r.kernel.org,
	Greg KH <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Joe Perches <joe@...ches.com>,
	Tiago Natel de Moura <tiago4orion@...il.com>
Subject: Re: [PATCH] documentation: add kernel-dot.emacs.txt

Hello,

2016-02-16 15:10 GMT-03:00 Tiago Natel de Moura <tiago4orion@...il.com>:
> Hello folks,
>
> The patch have some problem with the c-mode-hook setup, in the usage of
> c-cleanup-list. On my emacs24 it throw the following error:
>
> "Invalid indentation setting for symbol c-cleanup-list"
>
> After talk with Geyslan, he found the problem and pointed out a solution,
> then everything worked as expected.

Thank you Natel, I'm sending a v2 for this with your review.

>
>
> Thanks!
>
> This patch adds kernel-dot-emacs.txt (elisp) which deliver best
> indentation, comments and white space highlighting functionalities.
>
> This also changes the CodingStyle and 00-INDEX files by referencing
> the new kernel-dot-emacs.
>
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
> ---
>
> Notes:
>     This patch was done by suggestion of Jonathan Corbet:
>     http://thread.gmane.org/gmane.linux.documentation/35265/focus=35309
>
>  Documentation/00-INDEX             |   2 +
>  Documentation/CodingStyle          |  38 +----
>  Documentation/kernel-dot-emacs.txt | 285 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 291 insertions(+), 34 deletions(-)
>  create mode 100644 Documentation/kernel-dot-emacs.txt
>
> diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
> index cd077ca..d4c48f5 100644
> --- a/Documentation/00-INDEX
> +++ b/Documentation/00-INDEX
> @@ -259,6 +259,8 @@ kernel-doc-nano-HOWTO.txt
>         - mini HowTo on generation and location of kernel documentation files.
>  kernel-docs.txt
>         - listing of various WWW + books that document kernel internals.
> +kernel-dot-emacs.txt
> +       - emacs dot file for kernel coding style.
>  kernel-parameters.txt
>         - summary listing of command line / boot prompt args for the kernel.
>  kernel-per-CPU-kthreads.txt
> diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
> index c06f817..4d64b58 100644
> --- a/Documentation/CodingStyle
> +++ b/Documentation/CodingStyle
> @@ -501,40 +501,10 @@ typing - an infinite number of monkeys typing into GNU emacs would never
>  make a good program).
>
>  So, you can either get rid of GNU emacs, or change it to use saner
> -values.  To do the latter, you can stick the following in your .emacs file:
> -
> -(defun c-lineup-arglist-tabs-only (ignored)
> -  "Line up argument lists by tabs, not spaces"
> -  (let* ((anchor (c-langelem-pos c-syntactic-element))
> -         (column (c-langelem-2nd-pos c-syntactic-element))
> -         (offset (- (1+ column) anchor))
> -         (steps (floor offset c-basic-offset)))
> -    (* (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")))))
> -
> -This will make emacs go better with the kernel coding style for C
> -files below ~/src/linux-trees.
> +values. To do the latter, you can stick the elisp code from
> +Documentation/kernel-dot-emacs.txt in your emacs init file. This will make
> +emacs go better with the kernel coding style for C files below
> +~/src/linux-trees.
>
>  But even if you fail in getting emacs to do sane formatting, not
>  everything is lost: use "indent".
> diff --git a/Documentation/kernel-dot-emacs.txt b/Documentation/kernel-dot-emacs.txt
> new file mode 100644
> index 0000000..b6d6816
> --- /dev/null
> +++ b/Documentation/kernel-dot-emacs.txt
> @@ -0,0 +1,285 @@
> +;; Kernel dot emacs
> +;; Based on the prior elisp from Documentantion/CodingStyle
> +;;
> +;; January, 2016
> +;; Geyslan G. Bem <geyslan@...il.com>
> +
> +;; This elisp does use of emacs functionalities which deliver to the
> +;; user indentation, comments and white space highlighting.
> +;;
> +;; As known tabs are the higher law and the prior elisp code enforces
> +;; that law for any lineup indentation.
> +;;
> +;; However some trees have specific rules about line continuation
> +;; indentation. Even scripts/checkpatch.pl suggests the TABS+SPACES (lining up
> +;; under the open paren) for lineup the sequential lines.
> +;;
> +;; In addition to allowing the automatic setup by tree, this elisp can easily
> +;; be modified for new configurations. Eg.
> +;;
> +;;         (when (or (string-match (concat source-path "/net") filename)
> +;;                   (string-match (concat source-path "/drivers/net") filename))
> +;;           (setup-kernel-style 'extra-bottom-line t nil))
> +;;
> +;; The above model can be used for a new tree just changing the tree path
> +;; and parameters of setup-kernel-style function.
> +;;
> +;; setup-kernel-style function sets the kernel-comment-style,
> +;; kernel-lineup-tabs-only and kernel-lineup-maximum-tabs variables. They
> +;; are used by the functions kernel-comment-dwim and kernel-lineup-arglist.
> +;;
> +;; The kernel-lineup-arglist function detects the maximum tabs allowed to
> +;; lineup and if it must use tabs and spaces instead of only tabs.
> +;;
> +;; There are two cleanups for else and else if braces enabled when
> +;; auto-newline is on. These are comfortable and avoid wrong coding
> +;; style. For instance
> +;;
> +;; void spam(int i)
> +;; {
> +;;         if (i == 7) {
> +;;                 dosomething();
> +;;             ...
> +;;         }
> +;;         else
> +;;                         {
> +;; appears like this after the last open brace is typed:
> +;;
> +;; void spam(int i)
> +;; {
> +;;         if (i == 7) {
> +;;                 dosomething();
> +;;             ...
> +;;         } else {
> +;;
> +;; The same happens for else if opening braces.
> +;;
> +;; The function kernel-align-to-equals makes the aligning of variable
> +;; initializations/assignments easier.
> +;;
> +;;         int x = 10;
> +;;         char *str = "text";
> +;;         x = 100;
> +;;
> +;; After marked the region and pressed C-c a =
> +;;
> +;;         int x           = 10;
> +;;         char *str       = "text";
> +;;         x               = 100;
> +;;
> +;; Concerning to comments kernel-comment-dwim is an improved version of
> +;; comment-dwim. It comment/uncomment lines, regions or adds a new
> +;; indented comment after the code using the same key binding. Eg.
> +;;
> +;; void f(int x, int y);
> +;;
> +;; Press M-; in any position on the line for
> +;;
> +;; void f(int x, int y);   /*  */
> +;;
> +;; Press M-; again for
> +;;
> +;; /* void f(int x, int y); */
> +;;
> +;; Press M-; and again for
> +;;
> +;; void f(int x, int y);
> +;;
> +;; For multi-line comments the result is
> +;;
> +;; /*
> +;;  * void f1(int x, int y);
> +;;  * void f2(int x, int y);
> +;;  */
> +;;
> +;; Emacs doesn't provide yet a 'net' comment style by default. This code
> +;; also does the magic when kernel-comment-style is set as 'extra-bottom-line.
> +;;
> +;; /* void f1(int x, int y);
> +;;  * void f2(int x, int y);
> +;;  */
> +;;
> +;; Until now the comment-region doesn't tabify the comment, generating
> +;; spaces before the " * " comment-continue variable (this issue was
> +;; reported and patched in the to be released emacs-25) however this code
> +;; correctly tabify the commented result.
> +;;
> +;; kernel-comment-dwim also removes trailing white spaces created by the
> +;; comment-region.
> +;;
> +;; Finally the white space highlighting is a must to alert about long
> +;; lines, leading or trailing spaces and top or bottom empty lines.
> +
> +
> +(defconst kernel-column-limit 80
> +  "It is only 80, get over it.")
> +
> +(defvar kernel-source-path "~/src/linux-trees"
> +  "The kernel source path.")
> +
> +(defvar kernel-comment-style 'extra-lines
> +  "Default style is 'extra-lines.
> +The another option is 'extra-bottom-line")
> +(make-variable-buffer-local 'kernel-comment-style)
> +
> +(defvar kernel-lineup-tabs-only nil
> +  "If it is non-nil the kernel lineup indentation will make use of tabs only.
> +When nil lineup indentation will use TABS + SPACES.")
> +(make-variable-buffer-local 'kernel-lineup-tabs-only)
> +
> +(defvar kernel-lineup-maximum-tabs nil
> +  "If it is non-nil its value will be the maximum tabs steps in kernel lineup
> +indentation.
> +When nil there will not be such a limit.
> +In both cases there is also the maximum limit forced by the
> +`kernel-lineup-arglist' function in conjuction with the
> +`kernel-column-limit' constant.")
> +(make-variable-buffer-local 'kernel-lineup-maximum-tabs)
> +
> +(defun setup-kernel-style (comment-style lineup-tabs-only lineup-maximum-tabs)
> +  (setq kernel-comment-style comment-style)
> +  (setq kernel-lineup-tabs-only lineup-tabs-only)
> +  (setq kernel-lineup-maximum-tabs lineup-maximum-tabs))
> +
> +(defun kernel-comment-dwim ()
> +  "Comments or uncomments the region.
> +If there's no active region adds/indents an one line comment or
> +comments/uncomments the current line if the one line comment is
> +empty."
> +  (interactive)
> +  (let (beg end)
> +    (if (region-active-p)
> +        (progn
> +          (setq beg (region-beginning)
> +                end (region-end))
> +          (if (comment-only-p beg end)
> +              (uncomment-region beg end)
> +            (progn
> +              (comment-region beg end)
> +              (save-excursion
> +                (goto-char beg)
> +                ;; Remove extra top line
> +                (when (equal kernel-comment-style 'extra-bottom-line)
> +                  (re-search-forward "/\\*\\s-*\n\\s-*\\(\\*\\)" end t)
> +                  (replace-match "/\\1"))
> +                ;; Update end point
> +                (goto-char beg)
> +                (re-search-forward "\\*/" nil t)
> +                (setq end (point))
> +                ;; This error is fixed in version 25.
> +                (when (< emacs-major-version 25)
> +                  (tabify beg end))
> +                ;; Cleaning only trailing spaces inserted by comment-region.
> +                ;; Existing ones are not touched.
> +                (goto-char beg)
> +                (while (re-search-forward
> +                        "\\(/+\\|^\\s-+\\)\\(\\*\\)\\(\\s-+$\\)" end t nil)
> +                  (replace-match "\\1\\2")
> +                  (save-excursion
> +                    (re-search-forward "\\*/" nil t 1)
> +                    (setq end (point))))))))
> +      (progn
> +        (setq beg (line-beginning-position)
> +              end (line-end-position))
> +        (if (save-excursion
> +              (goto-char beg)
> +              (looking-at "\\s-*$"))
> +            (progn
> +              (comment-indent)
> +              (indent-according-to-mode))
> +          (if (comment-only-p beg end)
> +              (uncomment-region beg end)
> +            (if (save-excursion
> +                  (goto-char beg)
> +                  (re-search-forward "/\\*\\s-+\\*/" end t 1))
> +                (progn
> +                  (save-excursion
> +                    (goto-char beg)
> +                    (let (kill-ring)
> +                      (comment-kill nil)))
> +                  ;; Read end position directly
> +                  (comment-region beg (line-end-position)))
> +              (comment-indent))))))))
> +
> +(defun kernel-align-to-equals (begin end)
> +  "Align region to equal signs"
> +  (interactive "r")
> +  (align-regexp begin end "\\(\\s-*\\)=" 1 1 nil))
> +
> +(defun kernel-lineup-arglist (langelem)
> +  ""
> +  (let* ((ret (c-lineup-arglist langelem))
> +         (anchor (c-langelem-pos c-syntactic-element))
> +         (column (c-langelem-2nd-pos c-syntactic-element))
> +         (offset (- (1+ column) anchor))
> +         (newcol (c-langelem-col langelem t))
> +         (steps (floor offset c-basic-offset)))
> +    (if (not kernel-lineup-tabs-only)
> +        ret
> +      (progn
> +        (when (>= (+ newcol (* c-basic-offset steps))
> +                  kernel-column-limit)
> +          (setq steps (1- steps)))
> +        (when kernel-lineup-maximum-tabs
> +          (setq steps (min steps
> +                           kernel-lineup-maximum-tabs)))
> +        (* (max steps 1) c-basic-offset)))))
> +
> +(add-hook 'c-mode-common-hook
> +          (lambda ()
> +            (c-add-style
> +             "linux-kernel"
> +             '("linux" (c-offsets-alist
> +                        (arglist-cont-nonempty
> +                         c-lineup-gcc-asm-reg
> +                         kernel-lineup-arglist)
> +                        (c-cleanup-list brace-else-brace
> +                                        brace-elseif-brace))))))
> +
> +(defun kernel-style-hook ()
> +  (let ((filename (buffer-file-name))
> +        (source-path (expand-file-name kernel-source-path)))
> +    ;; Enable kernel mode for the appropriate files
> +    (when (and filename
> +               (string-match source-path filename))
> +      ;; Setup style
> +      (c-set-style "linux-kernel")
> +      (setq tab-width 8
> +            comment-style 'extra-line
> +            indent-tabs-mode t
> +            backward-delete-char-untabify-method nil)
> +      (c-toggle-auto-newline t)
> +
> +      ;; Setup tree paths here
> +      (when (or (string-match (concat source-path "/net") filename)
> +                (string-match (concat source-path "/drivers/net") filename))
> +        (setup-kernel-style 'extra-bottom-line t nil))
> +      (when (string-match (concat source-path "/drivers/usb/host") filename)
> +        (setup-kernel-style 'extra-lines t 2))
> +
> +      ;; Set kernel style key bindings
> +      (local-set-key [remap comment-dwim] 'kernel-comment-dwim)
> +      (local-set-key (kbd "C-c a =") 'kernel-align-to-equals)
> +      ;; Setup white space highlighting
> +      (require 'whitespace)
> +      (setq whitespace-line-column kernel-column-limit
> +            whitespace-style '(face empty
> +                                    indentation::tab
> +                                    whitespace-space-before-tab
> +                                    space-before-tab::tab
> +                                    lines-tail
> +                                    trailing))
> +      (dolist (face '(whitespace-line
> +                      whitespace-indentation
> +                      whitespace-space
> +                      whitespace-space-before-tab
> +                      whitespace-empty
> +                      whitespace-trailing))
> +        (set-face-background face "red"))
> +      (set-face-attribute whitespace-line nil
> +                          :background "red"
> +                          :foreground "yellow"
> +                          :weight 'bold)
> +      (whitespace-mode t))))
> +
> +(add-hook 'c-mode-hook 'kernel-style-hook)
> --
> 2.7.0
>



-- 
Regards,

Geyslan G. Bem
hackingbits.com

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