Re: [PATCH v2 1/5] byteorder: fix {BIG,LITTLE}_ENDIAN defines

[Antony Pavlov <antonynpavlov@gmail.com>]

On 29 June 2012 11:25, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Thu, Jun 28, 2012 at 10:32:30PM +0400, Antony Pavlov wrote:
>> In the Linux kernel sources the only one byteorder macro
>> can be defined (__BIG_ENDIAN or __LITTLE_ENDIAN) at a time.
>>
>> In barebox we have the __BIG_ENDIAN and __LITTLE_ENDIAN macros
>> defined simultaneously introduced in
>>
>>     commit 9ad1fe64abb12baac918ec177d9a52bbf2980d16
>>     Author: Baruch Siach <baruch@tkos.co.il>
>>     Date:   Sun Jun 27 08:46:05 2010 +0300
>>
>>       byteorder: add missing {BIG,LITTLE}_ENDIAN defines
>>
>>       This fixes build warnings when testing __BYTE_ORDER
>>       of the other kin
>>
>> But in arch/mips/lib/libgcc.h (from Linux) we have
>>
>>  #ifdef __BIG_ENDIAN
>>  struct DWstruct {
>>          int high, low;
>>  };
>>  #elif defined(__LITTLE_ENDIAN)
>>  struct DWstruct {
>>          int low, high;
>>  };
>>  #else
>>  #error I feel sick.
>>  #endif
>>
>> This means that regardless of current byteorder the big-endian
>> DWstruct will be selected. By turn this breaks the __lshrdi3()
>> function and the clocksource code on little-endian MIPS.
>>
>> Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
>> ---
>>  drivers/ata/disk_ata_drive.c      |    2 +-
>>  drivers/nor/cfi_flash.c           |    6 +++---
>>  include/cramfs/cramfs_fs.h        |    4 ++--
>>  include/envfs.h                   |   16 ++++++++++++----
>>  include/linux/byteorder/generic.h |    7 -------
>>  include/usb/usb.h                 |    2 +-
>>  6 files changed, 19 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/ata/disk_ata_drive.c b/drivers/ata/disk_ata_drive.c
>> index 4602af3..d5c5837 100644
>> --- a/drivers/ata/disk_ata_drive.c
>> +++ b/drivers/ata/disk_ata_drive.c
>> @@ -231,7 +231,7 @@ static void __maybe_unused ata_dump_id(uint16_t *id)
>>   */
>>  static void ata_fix_endianess(uint16_t *buf, unsigned wds)
>>  {
>> -#if __BYTE_ORDER == __BIG_ENDIAN
>> +#ifdef __BIG_ENDIAN
>>       unsigned u;
>>
>>       for (u = 0; u < wds; u++)
>> diff --git a/drivers/nor/cfi_flash.c b/drivers/nor/cfi_flash.c
>> index 654e647..02340e6 100644
>> --- a/drivers/nor/cfi_flash.c
>> +++ b/drivers/nor/cfi_flash.c
>> @@ -82,7 +82,7 @@ static void flash_add_byte (struct flash_info *info, cfiword_t * cword, uchar c)
>>               return;
>>       }
>>
>> -#if __BYTE_ORDER == __BIG_ENDIAN
>> +#ifdef __BIG_ENDIAN
>>       *cword = (*cword << 8) | c;
>>  #else
>>
>> @@ -167,7 +167,7 @@ static void flash_printqry (struct cfi_qry *qry)
>>  uchar flash_read_uchar (struct flash_info *info, uint offset)
>>  {
>>       uchar *cp = flash_make_addr(info, 0, offset);
>> -#if __BYTE_ORDER == __LITTLE_ENDIAN
>> +#ifdef __LITTLE_ENDIAN
>>       return flash_read8(cp);
>>  #else
>>       return flash_read8(cp + info->portwidth - 1);
>> @@ -195,7 +195,7 @@ static ulong flash_read_long (struct flash_info *info, flash_sect_t sect, uint o
>>               debug ("addr[%x] = 0x%x\n", x, flash_read8(addr + x));
>>       }
>>  #endif
>> -#if __BYTE_ORDER == __LITTLE_ENDIAN
>> +#ifdef __LITTLE_ENDIAN
>>       retval = ((flash_read8(addr) << 16) |
>>                 (flash_read8(addr + info->portwidth) << 24) |
>>                 (flash_read8(addr + 2 * info->portwidth)) |
>> diff --git a/include/cramfs/cramfs_fs.h b/include/cramfs/cramfs_fs.h
>> index af2940b..a7e9504 100644
>> --- a/include/cramfs/cramfs_fs.h
>> +++ b/include/cramfs/cramfs_fs.h
>> @@ -88,7 +88,7 @@ struct cramfs_super {
>>  #error "No byte order defined in __BYTE_ORDER"
>>  #endif
>>
>> -#if __BYTE_ORDER == __LITTLE_ENDIAN
>> +#ifdef __LITTLE_ENDIAN
>>  #define CRAMFS_16(x) (x)
>>  #define CRAMFS_24(x) (x)
>>  #define CRAMFS_32(x) (x)
>> @@ -96,7 +96,7 @@ struct cramfs_super {
>>  #define CRAMFS_GET_OFFSET(x) ((x)->offset)
>>  #define CRAMFS_SET_OFFSET(x,y)       ((x)->offset = (y))
>>  #define CRAMFS_SET_NAMELEN(x,y) ((x)->namelen = (y))
>> -#elif __BYTE_ORDER ==__BIG_ENDIAN
>> +#elif defined(__BIG_ENDIAN)
>>  #ifdef __KERNEL__
>>  #define CRAMFS_16(x) swab16(x)
>>  #define CRAMFS_24(x) ((swab32(x)) >> 8)
>> diff --git a/include/envfs.h b/include/envfs.h
>> index 67b8902..cb1c648 100644
>> --- a/include/envfs.h
>> +++ b/include/envfs.h
>> @@ -38,6 +38,11 @@ struct envfs_super {
>>  #error "No byte order defined in __BYTE_ORDER"
>>  #endif
>>
>> +#if __BYTE_ORDER != __LITTLE_ENDIAN && __BYTE_ORDER != __BIG_ENDIAN
>> +#error "__BYTE_ORDER must be __LITTLE_ENDIAN or __BIG_ENDIAN"
>> +#endif
>
> On Big Endian systems __LITTLE_ENDIAN is undefined and this results in:
>
> In file included from common/environment.c:37:
> include/envfs.h:41:21: warning: "__LITTLE_ENDIAN" is not defined

You are right.

>> +
>> +#ifdef __LITTLE_ENDIAN
>
> As said, this file is included from scripts/bareboxenv.c which is
> compiled for userspace. __LITTLE_ENDIAN will always be defined in
> userspace.

But it included from common/environment.c too!

Moreover, in my company there is Processor Core Testing Department.
These folks like to rebuild full MIPS Linux distribution on our
big-endian MIPS system natively just for testing purposes. So, I have
a chance to build MIPS barebox on big-endian system :))

>
> --
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-- 
Best regards,
  Antony Pavlov

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