xiaoxiang781216 commented on PR #16789:
URL: https://github.com/apache/nuttx/pull/16789#issuecomment-3139030371
> @xiaoxiang781216 first I would like to thank you for reviewing this PR so
fast.
>
> Regarding the mtd_proxy approach I still have my doubts: when a flash wear
levelling library like dhara or nvblk is inserted the direct link between the
mtd and block device is broken. And I don't think it is possible to use direct
mtd writing/reading and block writing/reading at the same time.
Yes, the direct mode isn't suitable for the advanced wear leveling algo like
dhara/nvblk since both save the meta data into flash. The direct mode will
destroy this critical information.
> Suppose you would like to `dd` into the mtd device resp. the block device,
they have a complete different meaning: `dd` into the mtd device would be a
change on the hardware directly, `dd` into the block device would be writing
blocks. How to differentiate between these two ?
>
> I think the same problem might exist for nand flashes (but I haven't
checked the ftl thoroughly).
>
But since ftl doesn't save any meta data into flash, so the direct mode(skip
buffer and erase) works well with it in some special user case.
> I remember that you made a remark that `ftl_initialize` should not be
called from a board startup, but I didn't quite understand this. Could you
explain this a little more?
That's because fs layer will add FTL wrapper on mtd device automatically
when the user open /dev/mtdblockx, which equal to you call ftl_initialize in
board file manually.
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