DOC filesystem questions

[David Woodhouse]

On Wed, 2003-08-06 at 05:27, Chuck Meade wrote:
> I have a DiskOnChip device soldered onto a PowerPC target and
> would appreciate if someone could verify if I am using the 
> correct commands to put a filesystem on it.
> 
> Also I am concerned from what I have read in the archives about
> the bad block table.  From what I see in the archives and in
> Karim Yaghmour's book, I needed to save this off.  Unfortunately
> however I cannot run DOS or its utilities on this target board,
> so I don't think that there is any way to do this.

You can read from /dev/mtd0 after first loading the DiskOnChip driver.
It's in there somewhere (see the NFTL and nftl_format code for more
details of precisely where). In fact, you could probably hack nftldump
to dump it, quite easily. 

> I use the following commands:
> 
>   nftl_format /dev/mtd0
>   fdisk /dev/nftla

Not without 'insmod nftl' or 'reboot -f' between them, I hope.

> 1. Have I destroyed any bad block table in the device by
>    doing this command sequence?

Yes.

> 2. If so, is this a bad block table needed by firmware
>    internal to the DOC, or just needed by some DOS utilities
>    that I won't be using anyway?

Neither. It's a bad block table needed by _all_ DiskOnChip drivers,
including the Linux driver. There is no firmware internal to the DOC now
-- there used to be a BIOS driver in there but you've removed it.

The bad block table is there to prevent the drivers from using blocks
which were marked bad during the factory testing. 

> 3. What I would really prefer to use is JFFS2 on this DOC.
>    I have seen messages from David that this may now be 
>    possible.

It's becoming possible. Give me a few weeks.

>    When I use other targets with NOR flash I typically write
>    an MTD partition map file for the target, then I use dd to
>    put my jffs2 image file into the right mtdblock partition.
>    How would I do this with a DOC device?

See a response I sent to the list a week or so ago -- basically we don't
currently do partitioning on the DiskOnChip's _raw_ flash, although
there's a patch around which hacks up hardcoded partitions, and the
INFTL format on the newest DiskOnChip units does seem to have a
partitioning scheme we might be able to abuse.


-- 
dwmw2