[PATCH 2/2] coding_style: Add case for enum as switch variable

[Yang Gu <yang.gu@intel.com>]

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---
 doc/coding-style.txt |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/doc/coding-style.txt b/doc/coding-style.txt
index 9e5a811..6fa355e 100644
--- a/doc/coding-style.txt
+++ b/doc/coding-style.txt
@@ -173,6 +173,38 @@ enum animal_type {
 	ANIMAL_TYPE_TWO_LEGS =		2,
 };
 
+M12: Enum as switch variable
+====================
+
+If the variable of a switch is an enum, you must not include a default in
+switch body. The reason for this is: If later on you modify the enum by adding
+a new type, and forget to change the switch accordingly, the compiler will
+complain the new added type hasn't been handled.
+
+Example:
+
+enum animal_type {
+	ANIMAL_TYPE_FOUR_LEGS =		4,
+	ANIMAL_TYPE_EIGHT_LEGS =	8,
+	ANIMAL_TYPE_TWO_LEGS =		2,
+};
+
+enum animal_type t;
+
+switch (t) {
+case ANIMAL_TYPE_FOUR_LEGS:
+	...
+	break;
+case ANIMAL_TYPE_EIGHT_LEGS:
+	...
+	break;
+case ANIMAL_TYPE_TWO_LEGS:
+	...
+	break;
+default:  // wrong
+	break;
+}
+
 O1: Shorten the name
 ====================
 Better to use abbreviation, rather than full name, to name a variable,
-- 
1.7.2.3