[PATCH] Codingstyle update

From: Michael Frank <mhf@linuxmail.org>

Documentation/CodingStyle

@@ -35,8 +35,41 @@ In short, 8-char indents make things easier to read, and have the added
 benefit of warning you when you're nesting your functions too deep.
 Heed that warning.
 
+Don't put multiple statements on a single line unless you have
+something to hide:
 
-		Chapter 2: Placing Braces
+	if (condition) do_this;
+	  do_something_everytime;
+
+Outside of comments, documentation and except in Kconfig, spaces are never
+used for indentation, and the above example is deliberately broken.
+
+Get a decent editor and don't leave whitespace at the end of lines.
+
+
+		Chapter 2: Breaking long lines and strings
+
+Coding style is all about readability and maintainability using commonly
+available tools.
+
+The limit on the length of lines is 80 columns and this is a hard limit.
+
+Statements longer than 80 columns will be broken into sensible chunks.
+Descendants are always substantially shorter than the parent and are placed
+substantially to the right. The same applies to function headers with a long
+argument list. Long strings are as well broken into shorter strings.
+
+void fun(int a, int b, int c)
+{
+	if (condition)
+		printk(KERN_WARNING "Warning this is a long printk with "
+						"3 parameters a: %u b: %u "
+						"c: %u \n", a, b, c);
+	else
+		next_statement;
+}
+
+		Chapter 3: Placing Braces
 
 The other issue that always comes up in C styling is the placement of
 braces.  Unlike the indent size, there are few technical reasons to
@@ -89,7 +122,7 @@ supply of new-lines on your screen is not a renewable resource (think
 comments on.
 
 
-		Chapter 3: Naming
+		Chapter 4: Naming
 
 C is a Spartan language, and so should your naming be.  Unlike Modula-2
 and Pascal programmers, C programmers do not use cute names like
@@ -122,7 +155,7 @@ problem, which is called the function-growth-hormone-imbalance syndrome.
 See next chapter.
 
 
-		Chapter 4: Functions
+		Chapter 5: Functions
 
 Functions should be short and sweet, and do just one thing.  They should
 fit on one or two screenfuls of text (the ISO/ANSI screen size is 80x24,
@@ -150,7 +183,44 @@ and it gets confused.  You know you're brilliant, but maybe you'd like
 to understand what you did 2 weeks from now.
 
 
-		Chapter 5: Commenting
+		Chapter 6: Centralized exiting of functions
+
+Albeit deprecated by some people, the equivalent of the goto statement is
+used frequently by compilers in form of the unconditional jump instruction.
+
+The goto statement comes in handy when a function exits from multiple
+locations and some common work such as cleanup has to be done.
+
+The rationale is:
+
+- unconditional statements are easier to understand and follow
+- nesting is reduced
+- errors by not updating individual exit points when making
+    modifications are prevented
+- saves the compiler work to optimize redundant code away ;)
+
+int fun(int )
+{
+	int result = 0;
+	char *buffer = kmalloc(SIZE);
+
+	if (buffer == NULL)
+		return -ENOMEM;
+
+	if (condition1) {
+		while (loop1) {
+			...
+		}
+		result = 1;
+		goto out;
+	}
+	...
+out:
+	kfree(buffer);
+	return result;
+}
+
+		Chapter 7: Commenting
 
 Comments are good, but there is also a danger of over-commenting.  NEVER
 try to explain HOW your code works in a comment: it's much better to
@@ -160,14 +230,14 @@ time to explain badly written code.
 Generally, you want your comments to tell WHAT your code does, not HOW.
 Also, try to avoid putting comments inside a function body: if the
 function is so complex that you need to separately comment parts of it,
-you should probably go back to chapter 4 for a while.  You can make
+you should probably go back to chapter 5 for a while.  You can make
 small comments to note or warn about something particularly clever (or
 ugly), but try to avoid excess.  Instead, put the comments at the head
 of the function, telling people what it does, and possibly WHY it does
 it.
 
 
-		Chapter 6: You've made a mess of it
+		Chapter 8: You've made a mess of it
 
 That's OK, we all do.  You've probably been told by your long-time Unix
 user helper that "GNU emacs" automatically formats the C sources for
@@ -205,29 +275,32 @@ has, which is why you need to give it a few command line options.
 However, that's not too bad, because even the makers of GNU indent
 recognize the authority of K&R (the GNU people aren't evil, they are
 just severely misguided in this matter), so you just give indent the
-options "-kr -i8" (stands for "K&R, 8 character indents"). 
+options "-kr -i8" (stands for "K&R, 8 character indents"), or use
+"scripts/Lindent", which indents in the latest style.
 
 "indent" has a lot of options, and especially when it comes to comment
-re-formatting you may want to take a look at the manual page.  But
+re-formatting you may want to take a look at the man page.  But
 remember: "indent" is not a fix for bad programming.
 
 
-		Chapter 7: Configuration-files
+		Chapter 9: Configuration-files
 
-For configuration options (arch/xxx/config.in, and all the Config.in files),
+For configuration options (arch/xxx/Kconfig, and all the Kconfig files),
 somewhat different indentation is used.
 
-An indention level of 3 is used in the code, while the text in the config-
-options should have an indention-level of 2 to indicate dependencies. The
-latter only applies to bool/tristate options. For other options, just use
-common sense. An example:
+Help text is indented with 2 spaces.
 
-if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
-   tristate 'Apply nitroglycerine inside the keyboard (DANGEROUS)' CONFIG_BOOM
-   if [ "$CONFIG_BOOM" != "n" ]; then
-      bool '  Output nice messages when you explode' CONFIG_CHEER
-   fi
-fi
+if CONFIG_EXPERIMENTAL
+	tristate CONFIG_BOOM
+	default n
+	help
+	  Apply nitroglycerine inside the keyboard (DANGEROUS)
+	bool CONFIG_CHEER
+	depends on CONFIG_BOOM
+	default y
+	help
+	  Output nice messages when you explode
+endif
 
 Generally, CONFIG_EXPERIMENTAL should surround all options not considered
 stable. All options that are known to trash data (experimental write-
@@ -235,7 +308,7 @@ support for file-systems, for instance) should be denoted (DANGEROUS), other
 experimental options should be denoted (EXPERIMENTAL).
 
 
-		Chapter 8: Data structures
+		Chapter 10: Data structures
 
 Data structures that have visibility outside the single-threaded
 environment they are created and destroyed in should always have
@@ -264,3 +337,87 @@ filesystem code ("struct super_block": s_count and s_active).
 
 Remember: if another thread can find your data structure, and you don't
 have a reference count on it, you almost certainly have a bug.
+
+
+		Chapter 11: Macros, Enums, Inline functions and RTL
+
+Names of macros defining constants and labels in enums are capitalized.
+
+#define CONSTANT 0x12345
+
+Enums are preferred when defining several related constants.
+
+CAPITALIZED macro names are appreciated but macros resembling functions
+may be named in lower case.
+
+Generally, inline functions are preferable to macros resembling functions.
+
+Macros with multiple statements should be enclosed in a do - while block:
+
+#define macrofun(a,b,c) 			\
+	do {					\
+		if (a == 5)			\
+			do_this(b,c);		\
+	} while (0)
+
+Things to avoid when using macros:
+
+1) macros that affect control flow:
+
+#define FOO(x)					\
+	do {					\
+		if (blah(x) < 0)		\
+			return -EBUGGERED;	\
+	} while(0)
+
+is a _very_ bad idea.  It looks like a function call but exits the "calling"
+function; don't break the internal parsers of those who will read the code.
+
+2) macros that depend on having a local variable with a magic name:
+
+#define FOO(val) bar(index, val)
+
+might look like a good thing, but it's confusing as hell when one reads the
+code and it's prone to breakage from seemingly innocent changes.
+
+3) macros with arguments that are used as l-values: FOO(x) = y; will
+bite you if somebody e.g. turns FOO into an inline function.
+
+4) forgetting about precedence: macros defining constants using expressions
+must enclose the expression in parentheses. Beware of similar issues with
+macros using parameters.
+
+#define CONSTANT 0x4000
+#define CONSTEXP (CONSTANT | 3)
+
+The cpp manual deals with macros exhaustively. The gcc internals manual also
+covers RTL which is used frequently with assembly language in the kernel.
+
+
+		Chapter 12: Printing kernel messages
+
+Kernel developers like to be seen as literate. Do mind the spelling
+of kernel messages to make a good impression. Do not use crippled
+words like "dont" and use "do not" or "don't" instead.
+
+Kernel messages do not have to be terminated with a period.
+
+Printing numbers in parentheses (%d) adds no value and should be avoided.
+
+
+		Chapter 13: References
+
+The C Programming Language, Second Edition
+by Brian W. Kernighan and Dennis M. Ritchie.
+Prentice Hall, Inc., 1988.
+ISBN 0-13-110362-8 (paperback), 0-13-110370-9 (hardback).
+
+The Practice of Programming
+Brian W. Kernighan, Rob Pike
+Addison-Wesley, 1999, ISBN 0-201-61586-X
+
+GNU manuals - where in compliance with K&R and this text - for cpp, gcc,
+gcc internals and indent, all available from www.gnu.org.
+
+--
+Last updated on 16 February 2004 by a community effort on LKML.