linux-kernel - Re: [PATCH 2/2] include: warn for inconsistent endian config definition

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Date:   Mon, 12 Jun 2017 22:51:23 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Babu Moger <babu.moger@...cle.com>
Cc:     kbuild test robot <lkp@...el.com>, kbuild-all@...org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        David Miller <davem@...emloft.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "moderated list:H8/300 ARCHITECTURE" 
        <uclinux-h8-devel@...ts.sourceforge.jp>,
        linux-m68k@...r.kernel.org, openrisc@...ts.librecores.org,
        Parisc List <linux-parisc@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Michal Simek <monstr@...str.eu>
Subject: Re: [PATCH 2/2] include: warn for inconsistent endian config definition

On Mon, Jun 12, 2017 at 10:30 PM, Babu Moger <babu.moger@...cle.com> wrote:
>
> Looks like microblaze can be configured to either little or big endian
> formats.  How about
> adding a choice statement to address this.
> Here is my proposed patch.

Hi Babu,

This part looks fine, but I think we also need this one:

diff --git a/arch/microblaze/Makefile b/arch/microblaze/Makefile
index 740f2b82a182..1f6c486826a0 100644
--- a/arch/microblaze/Makefile
+++ b/arch/microblaze/Makefile
@@ -35,6 +35,8 @@ endif
 CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_DIV) += -mno-xl-soft-div
 CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_BARREL) += -mxl-barrel-shift
 CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_PCMP_INSTR) += -mxl-pattern-compare
+CPUFLAGS-$(CONFIG_BIG_ENDIAN) += -mbig-endian
+CPUFLAGS-$(CONFIG_LITTLE_ENDIAN) += -mlittle-endian

 CPUFLAGS-1 += $(call cc-option,-mcpu=v$(CPU_VER))


That way, we don't have to guess what the toolchain does, but rather
tell it to do whatever is configured, like we do for most other architectures.

Unfortunately we can't do the same thing on xtensa, as that no longer
supports the -mbig-endian/-mbig-endian flags in any recent gcc version
(a long time ago it had them, but they were removed along with many other
options).

        Arnd