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Caught Sleeping at Work(queue) — Zephyr Podcast #050

By September 11, 2026No Comments

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Episode Summary

  • Three Picks From the ZDS Schedule: With the Zephyr Developer Summit about a month out, the schedule is live and worth a browse. Three that caught our eye: Ten Years of Zephyr: Replace Linux, or Work With It? from Iuliana Prodan, on running Zephyr and Linux side by side on one SoC versus replacing Linux outright; Zephyr Network Buffers from Johan Hedberg, who designed net_buf in the first place and whose session comes recommended by anyone who has ever handed a stack-allocated buffer to the USB stack and watched it get overwritten; and the Friday Linus Torvalds keynote with Dirk Hohndel.
  • Analog Devices to Acquire Alif: ADI announced an all-cash acquisition of Alif Semiconductor this week.
  • An Air Quality Sensor: A driver for the Plantower PMSA003I landed, covering PM1.0, PM2.5 and PM10 over I2C. No power management integration yet, which prompted a tangent on how much that actually buys you for a sensor that needs tens of seconds of warm-up before the readings stabilise anyway.
  • QEMU for Espressif Boards: QEMU targets for the Espressif DevKitC boards are in, covering the ESP32 along with the RISC-V based C3 and C6 and the S3. The emulation goes further than most of Zephyr’s QEMU targets, reaching the RTC and the CPU low power modes, for example. The catch is that it needs Espressif’s QEMU fork rather than the one in the Zephyr SDK.
  • Coredumps That See Every CPU: A freeze/thaw mechanism for SMP coredumps, contributed by AMD. When one core panics, the others are captured too, so the dump shows what the whole system was doing rather than one core’s view of it.
  • Don’t Sleep in the System Workqueue: A small change that opens a big topic: Modbus can now run its RX processing on a dedicated workqueue. The system workqueue executes one item at a time and everything ends up in it, so a driver that blocks on a slow I2C or UART transaction starves everything behind it. Nobody writes k_sleep() in there deliberately, but every bus transaction sleeps. Expect the same option to appear for the input drivers shortly, and there is an argument for a general Kconfig pattern rather than the copy-paste each subsystem does today.
  • CTF Traces in Perfetto: A script that converts Zephyr’s CTF traces to Perfetto, which removes the Babeltrace dependency and with it the “works on Linux only” problem. Related and landing around the same time: CTF traces are gaining a CPU field, without which an SMP trace is an unreadable interleaving of cores.
  • USB Host Mass Storage: Host-side mass storage is in progress. Plug in a USB stick and get a filesystem. It implements the classic bulk-only mass storage protocol rather than UAS, which is what modern USB 3 sticks actually speak.
  • Low Power on the STM32U3: Power management support for the STM32U3, one of ST’s ultra low power families.
  • WebAssembly as a Module: WebAssembly Micro Runtime is now documented as an external Zephyr module, so pulling it in is a west entry and a couple of Kconfigs. Apache licensed with the LLVM exception, six thousand stars, and a contributor list including Sony, Intel, Xiaomi and Siemens.
  • Single-Pair Ethernet: An ADIN1140 driver, a MAC and PHY in one package for single-pair Ethernet, needing only an SPI connection. The PR includes zperf numbers close to 10 Mbit, which is plenty for what these links are for.
  • The Arduino Nano R4: The Arduino Nano R4 is upstream: a Renesas RA4M1 Cortex-M4 at 48 MHz with 256 KB of flash and 32 KB of RAM, in the Nano footprint people actually want to drop into a project. After a run of larger and more expensive boards, this is Arduino doing the small thing again, for about the price of half a pizza in Dublin.