[PATCH v2 1/3] Revert "mtd: spi-nor: remove Fujitsu MB85RS1MT support"

[Ronan Dalton]

Hi,

On Fri, 2026-07-03 at 12:15 +0200, Miquel Raynal wrote:
> On 03/07/2026 at 07:45:56 +02, Richard Weinberger <richard at nod.at>
> wrote:
> 
> > ----- Ursprüngliche Mail -----
> > > Von: "Ronan Dalton" <Ronan.Dalton at alliedtelesis.co.nz>
> > > On Thu, 2026-07-02 at 07:39 +0200, Richard Weinberger wrote:
> > > > Do you really need (POSIX) file system semantics?
> > > > You could partition the FRAM into cells and then work with
> > > > them.
> > > > e.g. Just dd into it and erase it when needed...
> > > > Maybe the NVMEM cells mechanism needs some polishing but this
> > > > sounds
> > > > reasonable to me.
> > > 
> > > Yes, that could work for secrets storage. However we also store
> > > persistent logs and DHCP leases on this flash to minimize
> > > read/writes
> > > on the main flash, and this data is stored as files of varying
> > > lengths.
> > > A filesystem provides the most straightforward way of storing
> > > this data
> > > for us.
> > 
> > But the storage (FRAM) you chose is not suitable for any real
> > filesystem.
> > In a previous mail you said you use ext2 on it.
> > I have a hard time to see how using ext2 on top of mtdblock on an
> > FRAM
> > does not end in a disaster.
> > 
> > > That's not to say we couldn't develop some system of using the
> > > nvmem
> > > device as a backend for this data. This may be something we look
> > > at in
> > > the future.
> > 
> > Maybe FUSE can help with building a super simple filesystem which
> > provides
> > just enough to fulfill your use case.
> 
> The NVMEM cells mechanism is very flexible now with layouts. We do
> have
> support for ONIE Type-Length-Variable tables as well as an example of
> support for the environment variables in U-Boot. If you format very
> slightly your data you can very easily expose automatically one cell
> per
> information with a rather simple NVMEM layout driver and consume it
> this
> way.
> 
> Thanks,
> Miquèl

Thanks for your suggestions. We'll consider adapting our implementation
based on this information.

Regards,
Ronan.