[XEN PATCH v5 16/17] CODING_STYLE: Add a section on header guards naming conventions

[Alessandro Zucchelli <alessandro.zucchelli@xxxxxxxxxxx>]

This section explains which format should be followed by header
inclusion guards via a drop-down list of rules.

No functional change.

Signed-off-by: Alessandro Zucchelli <alessandro.zucchelli@xxxxxxxxxxx>

---
Changes in v5:
- edit inclusion guards naming conventions, according to feedback
  received
---
 CODING_STYLE | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/CODING_STYLE b/CODING_STYLE
index 7f6e9ad065..f4f26a3cd8 100644
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -159,6 +159,27 @@ Emacs local variables
 A comment block containing local variables for emacs is permitted at
 the end of files.  It should be:
 
+Header inclusion guards
+-----------------------
+
+Unless differently specified all header files should have proper inclusion
+guards in order to avoid being included multiple times.
+The following naming conventions have been devised:
+
+- private headers -> <dir>__<filename>_H
+    - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
+    - arch/arm/arm32/lib/something.h -> ARM__ARM32__LIB__SOMETHING_H
+    - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
+
+- asm-generic headers -> ASM_GENERIC__<filename>_H
+    - include/asm-generic/something.h -> ASM_GENERIC__SOMETHING_H
+
+- arch/<architecture>/include/asm/<subdir>/<filename>.h -> 
ASM__<architecture>__<subdir>__<filename>_H
+    - arch/x86/include/asm/something.h -> ASM__X86__SOMETHING_H
+
+- include/xen -> XEN__<filename>_H
+    - include/xen/something.h -> XEN__SOMETHING_H
+
 /*
  * Local variables:
  * mode: C
-- 
2.34.1