linux-kernel - Re: [microblaze-uclinux] Re: [PATCH v2 22/22] bitops: remove minix bitops from asm/bitops.h

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Message-ID: <4CC4C1B4.9090907@monstr.eu>
Date:	Mon, 25 Oct 2010 09:31:00 +1000
From:	Michal Simek <monstr@...str.eu>
To:	microblaze-uclinux@...e.uq.edu.au
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [microblaze-uclinux] Re: [PATCH v2 22/22] bitops: remove minix
 bitops from asm/bitops.h



Akinobu Mita wrote:
> 2010/10/22 Michal Simek <monstr@...str.eu>:
>> Akinobu Mita wrote:
>>> minix bit operations are only used by minix filesystem and useless
>>> by other modules. Because byte order of inode and block bitmaps is
>>> defferent on each architecture like below:
>>>
>>> m68k:
>>>       big-endian 16bit indexed bitmaps
>>>
>>> h8300, microblaze, s390, sparc, m68knommu:
>>>       big-endian 32 or 64bit indexed bitmaps
>> Just one small fix microblaze little endian support is ready for merging
>> to mainline which means that microblaze is
>> big-endian 32bit  and  little-endian 32bit
>>
>>> m32r, mips, sh, xtensa:
>>>       big-endian 32 or 64bit indexed bitmaps for big-endian mode
>>>       little-endian bitmaps for little-endian mode
>>>
>>> Others:
>>>       little-endian bitmaps
>>>
>>> In order to move minix bit operations from asm/bitops.h to
>>> architecture independent code in minix file system, this provides two
>>> config options.
>>>
>>> CONFIG_MINIX_FS_BIG_ENDIAN_16BIT_INDEXED is only selected by m68k.
>>> CONFIG_MINIX_FS_NATIVE_ENDIAN is selected by the architectures which
>>> use native byte order bitmaps (h8300, microblaze, s390, sparc,
>>> m68knommu, m32r, mips, sh, xtensa).
>>> The architectures which always use little-endian bitmaps do not select
>>> these options.
>> I haven't created any Kconfig option for little/big endian microblaze
>> but there should be a little bit different handling for MINIX_FS_NATIVE_ENDIAN
>> as you are describing above.
>> Anyway I think you don't need to reflect this in your patch because
>> we are not using that filesystem and I will write it to my to-do list and
>> will fix it later.
> 
> If upcomming microblade little-endian mode will use little-endian
> bitmaps for minixfs, microblade can continue to select
> CONFIG_MINIX_FS_NATIVE_ENDIAN and you don't need to change it.
> 
> But if it will use big-endian bitmaps, it may need some extra work
> to support it. Becuase there is no little-endian architecture
> which uses bit-endian bitmaps for minixfs.

As I wrote I don't know anybody who wants to use minixfs that's why we don't
need to do anything with it. I can test it but it has no high priority.

Michal




-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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