First cut at MTD/JFFS HOWTO
dwmw2 at infradead.org
Tue Feb 13 04:15:47 EST 2001
vmalik at danielind.com said:
> Q. Why another file system. What was wrong with ext2?
Standard response - need journalling pseudo-filesystem to emulate a block
device and to wear levelling. then need ext3 (note 3) on that. journalling
fs on top of journalling fs - not efficient. Also, no way for ext to
mark blocks as _deleted_ and no longer cared about. Fill ext2 partition on
NFTL, empty it again, and the NFTL will still carefully copy around the
blocks containing old deleted data.
> Q. Do I have to have JFFS on MTD?
ATM yes. Once you could do it on a block device. People are talking about
making me make it work on IDE devices (CF). But I don't want to :)
> Q. What is DOC (disk on chip)? A.
Bunch of NAND flash chips connected together with a clever ASIC which does
> Q. What File systems can I have on DOC? A.
If you put NFTL on it to emulate a block device (the status quo) then any
normal filesystem. JFFS ought to work too.
> Q. What is Flash memory? A.
> Q. What is CFI Flash memory? A.
> Q. What is JDEC Flash memory? A.
> Q. What is this "interleave" stuff? A.
If you have 16-bit chips, but a 32-bit processor, it makes sense to arrange
them side-by-side to fill the CPU's bus. You drive them both
simultaneously. That's the arrangement we refer to as 'interleave'.
Other possibilities are... 4x 8-bit chips on 32-bit bus, 2x8-bit
chips on 16-bit bus, ...
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