[PATCH 10/14] dev_vdbg() documentation

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From: David Brownell <[email protected]>

Update CodingStyle to talk about "-DDEBUG" message conventions and the
new "-DVERBOSE_DEBUG" convention.

Signed-off-by: David Brownell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
 Documentation/CodingStyle |   20 ++++++++++++++++++--
 1 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index a667eb1..7f1730f 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -633,12 +633,27 @@ 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 +805,5 @@ Kernel CodingStyle, by [email protected] at OLS 2002:
-Last updated on 2006-December-06.
+Last updated on 2007-July-13.

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