CodingStyle: relax the 80-cole rule

[sfrench/cifs-2.6.git] / Documentation / CodingStyle

diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index a667eb1fc26e2dfca7ac7b46b8a93f1eb22867e8..6caa146155788c8a67fc940c1879f2faf4fac1bb 100644 (file)
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -77,12 +77,15 @@ Get a decent editor and don't leave whitespace at the end of lines.
 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.
+The limit on the length of lines is 80 columns and this is a strongly
+preferred 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.
+argument list. Long strings are as well broken into shorter strings. The
+only exception to this is where exceeding 80 columns significantly increases
+readability and does not hide information.
 
 void fun(int a, int b, int c)
 {
@@ -633,12 +636,27 @@ covers RTL which is used frequently with assembly language in the kernel.
 
 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.
+words like "dont"; use "do not" or "don't" instead.  Make the messages
+concise, clear, and unambiguous.
 
 Kernel messages do not have to be terminated with a period.
 
 Printing numbers in parentheses (%d) adds no value and should be avoided.
 
+There are a number of driver model diagnostic macros in <linux/device.h>
+which you should use to make sure messages are matched to the right device
+and driver, and are tagged with the right level:  dev_err(), dev_warn(),
+dev_info(), and so forth.  For messages that aren't associated with a
+particular device, <linux/kernel.h> defines pr_debug() and pr_info().
+
+Coming up with good debugging messages can be quite a challenge; and once
+you have them, they can be a huge help for remote troubleshooting.  Such
+messages should be compiled out when the DEBUG symbol is not defined (that
+is, by default they are not included).  When you use dev_dbg() or pr_debug(),
+that's automatic.  Many subsystems have Kconfig options to turn on -DDEBUG.
+A related convention uses VERBOSE_DEBUG to add dev_vdbg() messages to the
+ones already enabled by DEBUG.
+
 
                Chapter 14: Allocating memory
 
@@ -790,4 +808,5 @@ Kernel CodingStyle, by greg@kroah.com at OLS 2002:
 http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/
 
 --
-Last updated on 2006-December-06.
+Last updated on 2007-July-13.
+