Re: [PATCH v2 0/2] mtd: devices: Qualcomm SCM storage support

[Junhao Xie]

On 2026/1/30 22:10, Miquel Raynal wrote:
> Hi,
>
> > > I don't believe you answered my question regarding how to access this
> > > interface from the kernel. On many of these devices we can find the MAC
> > > addresses of the system in the "DPP" partition. Do you have any ideas
> > > about how we could access this from within the kernel?
> > >
> > > Regards,
> > > Bjorn
> > I agree with your point. I will add a module param in v3 for default
> > read-only mode. e.g.: /sys/module/qcom_scm_storage/parameters/allow_write
> >
> > For something like the "DPP" partition, I think it's better to access it
> > from userspace than from kernel.
> If it's a MAC address that you are accessing, direct userspace does not
> sound like a good fit. If I may, NVMEM cells are there exactly for this
> purpose: identifying the content of a subpart of a storage device in a
> storage agnostic way. The NVMEM cells are made available to in-kernel
> drivers (ie. network devices have all the infrastructure to get the MAC
> address from there) and their content is also exposed to userspace
> through sysfs now.

Qualcomm's SPI-NOR boot firmware uses a GPT partition table. The "DPP"
partition contains a FAT file system, and the MAC address is stored in
one of these files.

Because the data is stored inside a filesystem rather than at a fixed
offset, it does not fit well with the NVMEM model, which assumes simple
offset-based access.

Accessing this would require the kernel to directly read files from a
filesystem, which is generally not appropriate, so this should probably
not be accessed from kernel.

> Thanks,
> Miquèl

Best regards,
Junhao Xie