Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=58637ec90b7ceed5909e726ac90118852f79d2b1
Commit:     58637ec90b7ceed5909e726ac90118852f79d2b1
Parent:     163ca88b9c5858909ee3f8801ae0096b5f94e835
Author:     Robert P. J. Day <[EMAIL PROTECTED]>
AuthorDate: Fri Dec 22 01:09:11 2006 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri Dec 22 08:55:49 2006 -0800

    [PATCH] Add a new section to CodingStyle, promoting include/linux/kernel.h
    
    Add a new section to the CodingStyle file, encouraging people not to
    re-invent available kernel macros such as ARRAY_SIZE(), FIELD_SIZEOF(),
    min() and max(), among others.
    
    Signed-off-by: Robert P. J. Day <[EMAIL PROTECTED]>
    Acked-by: Randy Dunlap <[EMAIL PROTECTED]>
    Acked-by: Jan Engelhardt <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 Documentation/CodingStyle |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 0ad6dcb..9069189 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -682,6 +682,24 @@ result.  Typical examples would be functions that return 
pointers; they use
 NULL or the ERR_PTR mechanism to report failure.
 
 
+               Chapter 17:  Don't re-invent the kernel macros
+
+The header file include/linux/kernel.h contains a number of macros that
+you should use, rather than explicitly coding some variant of them yourself.
+For example, if you need to calculate the length of an array, take advantage
+of the macro
+
+  #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+Similarly, if you need to calculate the size of some structure member, use
+
+  #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
+
+There are also min() and max() macros that do strict type checking if you
+need them.  Feel free to peruse that header file to see what else is already
+defined that you shouldn't reproduce in your code.
+
+
 
                Appendix I: References
 
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