FAT on raw Nand

FAT on raw Nand

[Gagan Prakash]

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.

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.

Thanks

Gagan Prakash

Re: FAT on raw Nand

[Charles Manning]

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.

Re: FAT on raw Nand

[David Woodhouse]

On Tue, 2005-09-20 at 13:32 +1200, Charles Manning wrote:
> 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-NFS' of which you speak is called 'PTP', and it's used by many
cameras.

-- 
dwmw2

Re: FAT on raw Nand -->PTP

[Charles Manning]

On Tuesday 20 September 2005 21:39, David Woodhouse wrote:
> On Tue, 2005-09-20 at 13:32 +1200, Charles Manning wrote:
> > 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-NFS' of which you speak is called 'PTP', and it's used by many
> cameras.

From a quick read of the USB PTP spec, it would seem that PTP is rather 
picture centric. Is that the case or can PTP also be used for more general 
data?

Re: FAT on raw Nand

[Simon Haynes]

On Monday 19 September 2005 23:36, 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.

A while ago I wrote a SSFDC traslation layer to do exactly this. It should be 
in the mtd CVS. To save myself time I restricted the development to exactly 
what I needed. This will probably mean you need to do some work to get
things going.

Cheers

Simon.