[uCsimm] FS on FLASH

From: 권석근 (kwonsk@mutech.co.kr)
Date: Sat Feb 26 2000 - 02:56:11 EST


Hi, all

I'm happy to introduce Writable File System on FLASH for uClinux.
Sometimes ago, i thought about how useful if could use FLASH memory
just like normal hard disk. Current romfs on flash could be ok for
most applications, but romfs has basic limitation. If i want to change
some configuration files for my application, i must re-generate romfs with
kernel
and download it, and it seemed to me uneasy.
Therefore i tryed to make writeable file system on flash about 3 months
and got success.

My code is based on the progress at MTD
(http://www.linux-mtd.infradead.org/ ).
It's scheme is msdos fs on the top of FTL (Flash Translation Layer?) on the
top of MTD device. i've reservered 512K bytes for this at the end of flash
memory and
made MTD driver for flash and did little hacking on msdos fs driver of
uClinux.
I've formatted /dev/ftla with mkdosfs and mount it /mnt. And GOT DOS disk.
I've tested some file copy and power-off and reboot. after mount /dev/ftla
on /mnt
i could also SEE it. yah, It works!

Maybe this work could be useful or just be a one of toy :-)
But i'm now preparing my patch and you could see my code someday.

note:
1, why msdos? -> After some test i realized that ext2fs did writing request
more
frequently even if i did not do anything (ex, file copy). this could be bad
for
FLASH. and msdosfs didnot try any writing if i do not try actual writing.
maybe ext2fs need some update for it's own purpose and it's too large to
hack for me.
2, for MTD on flash, kernel must be ram based. i've applied patch for ram
based kernel
(i could'nt memory right now where this patch comes from, but somewhere in
this mailing list)
even original romfs must be copyed to ramdisk. Well,, this could be a
panalty.

Thanks
kwonsk
kwonsk@mutech.co.kr

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