Re: [PATCH v6 1/9] block: partitions: of: Skip child nodes without reg property

[Loic Poulain]

Hi Rob,

On Tue, Jun 30, 2026 at 8:02 PM Rob Herring <robh@xxxxxxxxxx> wrote:
>
> On Mon, Jun 29, 2026 at 10:55:20AM +0200, Loic Poulain wrote:
> > Child nodes of a fixed-partitions node are not necessarily partition
> > entries, for example an nvmem-layout node has no reg property. The
> > current code passes a NULL reg pointer and uninitialized len to the
> > length check, which can result in a kernel panic or silent failure to
> > register any partitions.
>
> That does not sound right to me. A fixed-partitions node should only be
> defining partitions with address ranges. I would expect a partition node
> could be nvmem-layout, but not the whole address range. If you wanted
> the latter, then just do:
>
> partitions {
>   ...
> };
>
> nvmem-layout {
>   ...
> };

In our case, the nvmem-layout needs to be associated with a specific
eMMC hardware partition, nvmem cells can be a simple sub-range within
the global eMMC, each hardware partition (boot0, boot1, user...)
having its own address spaces.

That said, your point about not abusing fixed-partitions is valid. I
initially dropped the compatible = "fixed-partitions" from the
partitions-boot1 node when it only carries an nvmem-layout and no
actual partition entries, making it a plain named container node. But
it's a bit fragile if we want to support both nvmem-layout and
fixed-partitions.

Regarding your expectation of a partition node being a nvmem-layout,
do you mean that the nvmem-layout should live under a fixed-partitions
node? Something along these lines:

partitions-boot1 {
      compatible = "fixed-partitions";
      #address-cells = <1>;
      #size-cells = <1>;

      nvmem@4400 {
          reg = <0x4400 0x1000>;

          nvmem-layout {
              compatible = "fixed-layout";
              #address-cells = <1>;
              #size-cells = <1>;

              wifi_mac_addr: mac-addr@0 {
                  compatible = "mac-base";
                  reg = <0x0 0x6>;
                  #nvmem-cell-cells = <1>;
              };
      [...]

That makes some sense, this would require extra work for the
emmc/block layer to also associate fwnodes with logical partitions,
not just the whole disk/hw (hw part), Is that the direction you'd like
us to go?

Also, Note that regardless of which approach we settle on, this
specific fix/patch remains necessary to validate the partition node
and prevent NULL-deref.

Regards,
Loic