linux-kernel - [PATCH v3 3/3] include: warn for inconsistent endian config definition

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Date:   Thu,  6 Jul 2017 09:34:21 -0700
From:   Babu Moger <babu.moger@...cle.com>
To:     gregkh@...uxfoundation.org, ysato@...rs.sourceforge.jp,
        geert@...ux-m68k.org, jonas@...thpole.se,
        stefan.kristiansson@...nalahti.fi, shorne@...il.com,
        jejb@...isc-linux.org, deller@....de, davem@...emloft.net,
        viro@...iv.linux.org.uk, monstr@...str.eu
Cc:     mpe@...erman.id.au, peterz@...radead.org, mingo@...hat.com,
        jcmvbkbc@...il.com, linux-kernel@...r.kernel.org,
        uclinux-h8-devel@...ts.sourceforge.jp, linux-m68k@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        sparclinux@...r.kernel.org
Subject: [PATCH v3 3/3] include: warn for inconsistent endian config definition

We have seen some generic code use config parameter CONFIG_CPU_BIG_ENDIAN
to decide the endianness.

Here are the few examples.
include/asm-generic/qrwlock.h
drivers/of/base.c
drivers/of/fdt.c
drivers/tty/serial/earlycon.c
drivers/tty/serial/serial_core.c

Display warning if CPU_BIG_ENDIAN is not defined on big endian
architecture and also warn if it defined on little endian architectures.

Here is our original discussion
https://lkml.org/lkml/2017/5/24/620

Signed-off-by: Babu Moger <babu.moger@...cle.com>
Suggested-by: Arnd Bergmann <arnd@...db.de>
Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
 include/linux/byteorder/big_endian.h    |    4 ++++
 include/linux/byteorder/little_endian.h |    4 ++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/include/linux/byteorder/big_endian.h b/include/linux/byteorder/big_endian.h
index 3920414..ffd2159 100644
--- a/include/linux/byteorder/big_endian.h
+++ b/include/linux/byteorder/big_endian.h
@@ -3,5 +3,9 @@
 
 #include <uapi/linux/byteorder/big_endian.h>
 
+#ifndef CONFIG_CPU_BIG_ENDIAN
+#warning inconsistent configuration, needs CONFIG_CPU_BIG_ENDIAN
+#endif
+
 #include <linux/byteorder/generic.h>
 #endif /* _LINUX_BYTEORDER_BIG_ENDIAN_H */
diff --git a/include/linux/byteorder/little_endian.h b/include/linux/byteorder/little_endian.h
index 0805737..ba910bb 100644
--- a/include/linux/byteorder/little_endian.h
+++ b/include/linux/byteorder/little_endian.h
@@ -3,5 +3,9 @@
 
 #include <uapi/linux/byteorder/little_endian.h>
 
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#warning inconsistent configuration, CONFIG_CPU_BIG_ENDIAN is set
+#endif
+
 #include <linux/byteorder/generic.h>
 #endif /* _LINUX_BYTEORDER_LITTLE_ENDIAN_H */
-- 
1.7.1