[PATCH] Add a new section to CodingStyle, promoting include/linux/kernel.h.

["Robert P. J. Day" <rpjday@mindspring.com>]

  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 <rpjday@mindspring.com>

---

  NOTE:  at the moment, there is not a single invocation of the
FIELD_SIZEOF() macro anywhere in the entire source tree, so if someone
had a hankering to rename it to something more catchy, now would be a
good time and i can always resubmit the patch i sent in yesterday.



diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 0ad6dcb..a736333 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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