On Wed, Jul 2, 2025 at 3:50 AM Niklas Söderlund
<niklas.soderlund+renesas@xxxxxxxxxxxx> wrote:
>
> The dtc graph_child_address check can't distinguish between bindings
> where there can only be a single endpoint, and cases where there can be
> multiple endpoints.
>
> In cases where the bindings allow for multiple endpoints but only one is
> described false warnings about unnecessary #address-cells/#size-cells
> can be generated, but only if the endpoint described have an address of
> 0 (A), for single endpoints with a non-zero address (B) no warnings are
> generated.
>
> A)
> ports {
> #address-cells = <1>;
> #size-cells = <0>;
>
> port@0 {
> #address-cells = <1>;
> #size-cells = <0>;
>
> sourceA: endpoint@0 {
> reg = <0>
> };
> };
> };
>
> B)
> ports {
> #address-cells = <1>;
> #size-cells = <0>;
>
> port@0 {
> #address-cells = <1>;
> #size-cells = <0>;
>
> sourceB: endpoint@1 {
> reg = <1>
> };
> };
> };
>
> The false warnings, and especially the confusion on why it only triggers
> for single endpoints where the address is 0, leads to confused user and
> reports of issues with DTS files. To try and mitigate this behavior by
> demote the check to W=2 and document the possibility for false warnings
> in the check itself.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> ---
> Hi,
>
> This solution was lightly hinted at [1] by Rob and I have ran with it
> for a while locally and I'm happy with the result. Lets see what the
> rest of you think.
>
> 1. https://lore.kernel.org/all/20250109150327.GA3352888-robh@xxxxxxxxxx/
> ---
> scripts/Makefile.dtbs | 6 +++---
> scripts/dtc/checks.c | 5 +++++
dtc changes have to go upstream first. I can drop this when applying.
Rob
