My Week in Beagle #5

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Hello everyone. I was busy with the Linux kernel for most of the week. Let’s go over everything.

Devicetree append properties support

Currently, devictree supports creating and deleting properties but not appending to existing properties. This functionality is vital for complex uses like MikroBUS. I have been working on this for a while and posted Patch v3 last week.

To understand what it allows, let’s take an example:

dts-v1/;

/ {
    node {
        str-prop = "0";
    };
};

/ {
    node {
        /append-property/ str-prop = "1";
    };
};

The above devictree will produce the following output:

dts-v1/;

/ {
    node {
        str-prop = "0", "1";
    };
};

Devicetree overlays path reference support

Devicetree allows references in two contexts:

  1. Integer context: In this case the references are resolved to phandle. 
    foo = <&bar>;
  2. String context: In this case, the references are resolved to paths. 
    foo = &bar;

Runtime overlays only support the former but not the latter. I have created a patch series to fix this asymmetry.

Additionally, __symbols__ does not support phandles, which makes overlays modifying __symbols__ somewhat limiting. More context regarding this patch can be found here.

Ending Thoughts

This was it for this week. Hopefully, this helps bring transparency regarding where the development efforts are concentrated, and how the community can help. Look forward to next update.

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