big-endian sandbox issue

[Sascha Hauer]

On Wed, Jul 01, 2015 at 07:55:05AM +0300, Antony Pavlov wrote:
> Hi!
> 
> I have tried to build barebox on big-endian MIPS CPU running Debian 8.
> It fails because of unconditional <linux/byteorder/little_endian.h> inclusion.
> 
> At the first glance this can help:
> 
> --- a/arch/sandbox/include/asm/byteorder.h
> +++ b/arch/sandbox/include/asm/byteorder.h
> @@ -3,6 +3,12 @@
> 
>  #include <asm/types.h>
> 
> +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> +#include <linux/byteorder/big_endian.h>
> +#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
>  #include <linux/byteorder/little_endian.h>
> +#else
> +#error "__BYTE_ORDER__ != __ORDER_BIG_ENDIAN__ and __BYTE_ORDER__ !=
> __ORDER_LITTLE_ENDIAN__"
> +#endif

This change seems ok.

> 
>  #endif /* _I386_BYTEORDER_H */
> 
> But some warning appears:
> 
> In file included from common/filetype.c:21:0:
> /barebox.git/arch/sandbox/include/asm/unaligned.h:11:21: warning:
> "__LITTLE_ENDIAN" is not defined [-Wundef]
>  #if __BYTE_ORDER == __LITTLE_ENDIAN

This should be #ifdef __LITTLE_ENDIAN

The authoritive answer to this is in include/common.h:

/*
 * sanity check. The Linux Kernel defines only one of __LITTLE_ENDIAN and
 * __BIG_ENDIAN. Endianess can then be tested with #ifdef __xx_ENDIAN. Userspace
 * always defined both __LITTLE_ENDIAN and __BIG_ENDIAN and byteorder can then
 * be tested with #if __BYTE_ORDER == __xx_ENDIAN.
 *
 * As we tend to use a lot of Kernel code in barebox we use the kernel way of
 * determing the byte order. Make sure here that architecture code properly
 * defines it.
 */
#include <asm/byteorder.h>
#if defined __LITTLE_ENDIAN && defined __BIG_ENDIAN
#error "both __LITTLE_ENDIAN and __BIG_ENDIAN are defined"
#endif
#if !defined __LITTLE_ENDIAN && !defined __BIG_ENDIAN
#error "None of __LITTLE_ENDIAN and __BIG_ENDIAN are defined"
#endif

Sascha

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