Re: FAT on raw Nand

[Charles Manning <manningc2@actrix.gen.nz>]

On Tuesday 20 September 2005 10:36, Gagan Prakash wrote:
> Hi
>
> I am trying to solve the problem of allowing a device with raw nand to be
> exposed to any Desktop OS (OS 10, Windows and Linux) without having to
> install any sort of driver on the Desktop OS that is not already present.
> The only solution I have read of/come up with is for the device to act as
> USB external drive and let the host OS mount it as a FAT filesystem. This
> means that the filesystem on device partition that is exposed needs to be
> FAT.

If you can't install any drivers then FAT is probably the only way to go for a 
FS.

The only alternative I can think of to this is to use ethernet + nfs  instead. 
ie. Your device looks like a USB ethernet device with a host running nfs  on 
the other end. That would allow you to run an alternative FS like YAFFS.

>
> Now from the archives I know its not the easiest and safest thing to
> expose a partition as FAT on raw nand. And it also requires the writing of
> a FTL layer. I was wondering if there is a better solution for this
> problem.
>
> For example is there a way to emulate FAT on top of existing nand fs like
> YAFFS or JFFS2 (this would seem hard specially for writes). Or is the only
> solution is to format the device as FAT and expose it as an external USB
> drive to the host OS.

Unfortunately there is no USB-NFS. There is only a USB mass storage device 
which can be used with most block file systems (typically FAT). USB-NFS would 
have been a good idea because it would allow devices to use their own FS 
internally.

The USB Mass Storage spec has no notion of a file system, just read/write 
blocks of data. To use YAFFS etc on the device and make it look like a USB 
mass storage device running FAT is probably too much to ask.