linux-kernel - Re: [RFC PATCH 3/4] sh: define __BIG

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Date:   Thu, 3 Jun 2021 16:19:44 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [RFC PATCH 3/4] sh: define __BIG_ENDIAN for math-emu

On 6/3/21 12:54 AM, Geert Uytterhoeven wrote:
> Hi Randy,
> 
> On Thu, Jun 3, 2021 at 1:17 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>> The headers in include/math-emu/ test for __BYTE_ORDER == __BIG_ENDIAN
>> without checking to see if these macros are defined, so add
>> a define for __BIG_ENDIAN before pulling in these headers.
>>
>> This placates these build warnings:
>>
>> In file included from ../arch/sh/math-emu/math.c:23:
>> ../include/math-emu/single.h:50:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
>>    50 | #if __BYTE_ORDER == __BIG_ENDIAN
>> In file included from ../arch/sh/math-emu/math.c:24:
>> ../include/math-emu/double.h:59:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
>>    59 | #if __BYTE_ORDER == __BIG_ENDIAN
>>
>> Fixes: 4b565680d163 ("sh: math-emu support")
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> 
> Thanks for your patch!
> 
>> --- linux-next-20210528.orig/arch/sh/math-emu/sfp-util.h
>> +++ linux-next-20210528/arch/sh/math-emu/sfp-util.h
>> @@ -70,4 +70,4 @@
>>
>>  #define __BYTE_ORDER __LITTLE_ENDIAN
>>
>> -
>> +#define __BIG_ENDIAN 0
> 
> I don't think this is the right fix.
> 
> I think the right values should be picked up from:
> 
>     include/uapi/linux/byteorder/big_endian.h:#define __BIG_ENDIAN 4321
>     include/uapi/linux/byteorder/little_endian.h:#define __LITTLE_ENDIAN 1234
> 
> How is this picked up on other architectures using <math-emu/single.h>?

Hi Geert,

There isn't very much to compare to in other arch/.
I've made a v2 patch that is done like arch/nds32/ does.
What do you think about this one?

thanks.
---
From: Randy Dunlap <rdunlap@...radead.org>
Subject: [RFC PATCH 2/3 v2] sh: define __BIG_ENDIAN for math-emu

Fix this by defining both ENDIAN macros in
<asm/sfp-machine.h> so that they can be utilized in
<math-emu/soft-fp.h> according to the latter's comment:
/* Allow sfp-machine to have its own byte order definitions. */

(This is what is done in arch/nds32/include/asm/sfp-machine.h.)

This placates these build warnings:

In file included from ../arch/sh/math-emu/math.c:23:
../include/math-emu/single.h:50:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
   50 | #if __BYTE_ORDER == __BIG_ENDIAN
In file included from ../arch/sh/math-emu/math.c:24:
../include/math-emu/double.h:59:21: warning: "__BIG_ENDIAN" is not defined, evaluates to 0 [-Wundef]
   59 | #if __BYTE_ORDER == __BIG_ENDIAN

Fixes: 4b565680d163 ("sh: math-emu support")
Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
Cc: Rich Felker <dalias@...c.org>
Cc: linux-sh@...r.kernel.org
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
---
 arch/sh/include/asm/sfp-machine.h |    8 ++++++++
 1 file changed, 8 insertions(+)

--- linux-next-20210528.orig/arch/sh/include/asm/sfp-machine.h
+++ linux-next-20210528/arch/sh/include/asm/sfp-machine.h
@@ -13,6 +13,14 @@
 #ifndef _SFP_MACHINE_H
 #define _SFP_MACHINE_H
 
+#ifdef __BIG_ENDIAN__
+#define __BYTE_ORDER __BIG_ENDIAN
+#define __LITTLE_ENDIAN 0
+#else
+#define __BYTE_ORDER __LITTLE_ENDIAN
+#define __BIG_ENDIAN 0
+#endif
+
 #define _FP_W_TYPE_SIZE		32
 #define _FP_W_TYPE		unsigned long
 #define _FP_WS_TYPE		signed long