[Yaffs-archive] Re: Latest CVS

[Thomas Gleixner]

On Sunday 24 November 2002 01:10, Nick Bane wrote:
> I downloaded the latest mtd cvs and overwrote 2.4.19-rmk4 with the mtd
> parts from drivers/mtd and include/mtd. I then added back the fujitsu NAND
> part defs and the balloon specific NAND drivers modifying them to use the
> new orthodoxy using NAND_ECC_NONE and it is all just fine.
The mtdpart patch is redundant as mtdpart.c in mtd cvs contains the additions 
already, since 2-22-02.

You can also select NAND_ECC_SW as long as your filesystem driver is using 
either mtd->read /write or mtd->read/write_ecc with NAND_NONE_OOB, which is 
the case for YAFFS.mtd->read defaults to mtd_read_ecc (......., 
NAND_NONE_OOB). Same for mtd->write.

> I also support the per-mtd-partition rather than per-mtd-device ecc mode
> support as that would enable multiple file systems to reside on the same
> device. This would have been helpful to me during development. Instead I
> used two devices.
Multiple flesystems are supported since version 1.30, which was committed to 
mtd-cvs on 8-29-02. I have running a JFFS2 partition and a YAFFS partition on 
the same chip without any modifications to nand driver, JFFS2 and YAFFS.. 
JFFS2 uses nand driver builtin ECC and YAFFS uses it's own.

The driver supports runtime per partition selection, but not for the ECC_MODE. 
It supports the selection of ECC data placement in the oob area. Currently 
there are 3 placements supported:
NAND_NONE_OOB:	No ECC is calculated and placed in oob area
NAND_JFFS2_OOB:  calc ECC using the selected ECC-Mode and place the ECC data 
in the appropriate place for JFFS2 
NAND_YAFFS_OOB: calc ECC using the selected ECC-Mode and place the ECC data in 
the appropriate place for YAFFS

It makes _NO_ sense to select different ECC-Modes for one chip. If you have 
Hardware-ECC you will use it for your hole chip and you _CANNOT_ switch 
between the different hardware ECC modes, as your ECC generator has one fixed 
algorithm to build ECC. The only exception is a ECC, which is supplied by the 
filesystem and for that you can select NAND_NONE_OOB.

-- 
Thomas
____________________________________________________
linutronix - competence in embedded & realtime linux
http://www.linutronix.de
mail: tglx@linutronix.de


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