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

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Message-ID: <AANLkTikgRWWH0RhR2S5cFE+jkJbW30Arwsjic4UANuVd@mail.gmail.com>
Date:	Fri, 22 Oct 2010 16:55:10 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	monstr@...str.eu
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Ungerer <gerg@...inux.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Andreas Schwab <schwab@...ux-m68k.org>,
	linux-m68k@...ts.linux-m68k.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, linux-s390@...r.kernel.org,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	microblaze-uclinux@...e.uq.edu.au,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org,
	Hirokazu Takata <takata@...ux-m32r.org>,
	linux-m32r@...linux-m32r.org, Ralf Baechle <ralf@...ux-mips.org>,
	linux-mips@...ux-mips.org, Paul Mundt <lethal@...ux-sh.org>,
	linux-sh@...r.kernel.org, Chris Zankel <chris@...kel.net>
Subject: Re: [PATCH v2 22/22] bitops: remove minix bitops from asm/bitops.h

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.
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