Re: [PATCH v10 3/3] nvmem: core: Expose cells through sysfs

[Rafał Miłecki]

On 2023-09-22 19:48, Miquel Raynal wrote:
> The binary content of nvmem devices is available to the user so in the
> easiest cases, finding the content of a cell is rather easy as it is
> just a matter of looking at a known and fixed offset. However, nvmem
> layouts have been recently introduced to cope with more advanced
> situations, where the offset and size of the cells is not known in
> advance or is dynamic. When using layouts, more advanced parsers are
> used by the kernel in order to give direct access to the content of 
> each
> cell, regardless of its position/size in the underlying
> device. Unfortunately, these information are not accessible by users,
> unless by fully re-implementing the parser logic in userland.
>
> Let's expose the cells and their content through sysfs to avoid these
> situations. Of course the relevant NVMEM sysfs Kconfig option must be
> enabled for this support to be available.
>
> Not all nvmem devices expose cells. Indeed, the .bin_attrs attribute
> group member will be filled at runtime only when relevant and will
> remain empty otherwise. In this case, as the cells attribute group will
> be empty, it will not lead to any additional folder/file creation.
>
> Exposed cells are read-only. There is, in practice, everything in the
> core to support a write path, but as I don't see any need for that, I
> prefer to keep the interface simple (and probably safer). The interface
> is documented as being in the "testing" state which means we can later
> add a write attribute if though relevant.
>
> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>

Tested-by: Rafał Miłecki <rafal@xxxxxxxxxx>

# hexdump -C /sys/bus/nvmem/devices/u-boot-env0/cells/ipaddr@15c
00000000  31 39 32 2e 31 36 38 2e  31 2e 31                 
|192.168.1.1|
0000000b

--
Rafał Miłecki