Benjamin Cabé

Zephyr Weekly Update – Getting ready for Zephyr 3.5

Benjamin Cabé
Zephyr Weekly Update - October 6, 2023

Zephyr Weekly Update - October 6, 2023

Apologies for missing last week’s update. Last Friday was the feature freeze for Zephyr 3.5 and everyone, including myself, was pretty busy trying to push everything over the finish line!

Because of the feature freeze, no significant changes happened in the last week, so this update will still pretty much feel like a “weekly”, I guess 🙂 I will try to keep it short (…ish) since I am preparing a full write-up about what’s new in Zephyr 3.5, and I don’t want to spoil all the fun! I would also like to apologize to the Bluetooth contributors and maintainers in particular as I’m pretty sure I am missing important stuff — I definitely spotted lots of stabilization and bug fixing but if I forgot something important, please let me know in the comments or on Discord!

Also, remember to join Peter and me next Wednesday, Oct. 11, for our 3rd Zephyr Tech Talk, where we’ll discuss everything you need to know about Renode! I’d actually recommend you “RSVP” on LinkedIn, as this is the best way to make sure you will get a reminder as we go live. You can also of course spread the word in your network, if you feel like it.

Linkable loadable extensions (llext)

The newly introduced Linkable Loadable Extensions (llext) subsystem makes it possible to dynamically extend the functionality of an application at runtime. Extensions can be loaded from pre-compiled ELF formatted data which is verified, loaded, and linked with other extensions.

As often, an example is worth a thousand words and I encourage you to use the llext shell commands to get a feel of what it’s all about. A dedicated sample will give you all the instructions you need to build a “Hello World” binary, and then dynamically load it and invoke it using shell commands (there is even a command to load the hex-encoded binary, so you can actually do the whole thing without leaving your Zephyr shell!).

uart:~$ llext help
llext - Loadable extension commands
Subcommands:
  list          :List loaded extensions and their size in memory
  load_hex      :Load an elf file encoded in hex directly from the shell input.
                 Syntax:
                 <ext_name> <ext_hex_string>
  unload        :Unload an extension by name. Syntax:
                 <ext_name>
  list_symbols  :List extension symbols. Syntax:
                 <ext_name>
  call_fn       :Call extension function with prototype void fn(void). Syntax:
                 <ext_name> <function_name>

I am really excited about what’s going to come next now that one of the most requested feature since many years is basically unlocked. There’s still a lot that needs to be done (as an example, in this initial version, one may need to disable memory protection for llext to work…) but that makes things even more exciting! (PR #57086)

Binary descriptors

Binary descriptors are a new feature that makes it super simple to describe data objects (think: “model number” of your device, “kernel version”, etc.) that end up being linked at a known offset in your binary.

Like I just said, binary descriptors are really easy to use:

#include <zephyr/bindesc.h>

BINDESC_STR_DEFINE(app_version, BINDESC_ID_APP_VERSION_STRING, "1.2.3");

“Standard” binary descriptors such as build time, or kernel version, can be enabled without having to change anything in your code, just by enabling the dedicating Kconfig options.

A new west bindesc command has been introduced to allow developers to read binary descriptors in .bin, .hex, .elf, or .uf2 binary files.

You may want to check out the new code sample to familiarize yourself with the different macros and tools surrounding binary descriptors.

(PR #54464)

Object cores

Object cores are a new kernel debugging tool that can be used to both identify and perform operations on registered objects.

Kernel objects such as semaphores, message queues, etc. may now (if enabled via the dedicated CONFIG_OBJ_CORE_ * Kconfig options) embed a new “object core” that can be used to gather and access all sorts of statistics about the object.

The documentation page for this new feature is quite frankly excellent, so I would recommend you check it out as it’s gonna do a better job than I ever will at explaining things!

(PR #59075)

Boards & SoCs

Raspberry Pi Model 4 B

Drivers

HM330X particle sensor

Miscellaneous

A big thank you to the 21 individuals who had their first pull request accepted in the past 2 weeks, 💙 🙌: @moritzstoetter, @ivaniushkov, @fkwasowi, @nik012003, @meshium, @jandriea, @hlord2000, @wouterh, @srisurya1, @JeroenReeskamp, @bjda, @Fladdan, @zohavas, @lifenggitacc, @dcorbeil, @stasys0, @AirChandler, @lindblandro, @graffiti, @rahul-sin, and @tbr-tt.

As always, I very much welcome your thoughts and feedback in the comments below. See you in two weeks, as I don’t think next week will see any noteworthy update as the final release approaches.

If you enjoyed this article, don’t forget to subscribe to this blog to be notified of upcoming publications! And of course, you can also always find me on Twitter and Mastodon.

Catch up on all previous issues of the Zephyr Weekly Update:

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