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radio_esp32

The adapter between Espressif’s radio blobs and FlintOS.

Phase 3 of doc/plan-radio.md, issue #65.

What this is

Section titled “What this is”

Espressif’s Wi-Fi and BLE support ships as precompiled .a files built against FreeRTOS. They do not link against an RTOS directly — they call out through [osi::WifiOsiFuncs], a table of 115 function pointers covering tasks, queues, semaphores, event groups, allocation, interrupts and the PHY. This crate fills that table in.

Everything the object-model half needs already exists: kernel::dynobj (#58) and kernel::heap (#57) were built for exactly this and are host- and hardware-tested on their own. Most of what remains here is translation — FreeRTOS’s conventions into FlintOS’s — and the translation is where the bugs live, so each one is written down at the function that performs it.

The layer concession

Section titled “The layer concession”

This is the only crate in the tree permitted to name kernel. That is a deliberate, single exception recorded in tools/check-layers.sh: the blob demands a kernel’s object model, and the alternative to answering here is answering everywhere. If a second crate ever wants kernel, that is a signal to ask why rather than to widen the rule.

Status

Section titled “Status”

The table is complete: 115 of 115 on the target, and esp_wifi_init_internal returns ESP_OK on an ESP32-DevKitC. That is the first thing that has ever proved an entry right — a table can only be checked by the blob calling it, and until #67 nothing had.

What has not been proved is every entry: init exercises allocation, task creation, queues, semaphores, the PHY and the NVS family. Scan and associate (5.2, 5.3) are what reach the rest.

[WifiOsiFuncs::for_each_null] reports whatever is still null, by name. There is deliberately no hand-written list of gaps — there was one, and it was a year out of date; see the note above table().

The blobs are fetched, not vendored — make blobs pulls them at pinned revisions with checksums, and build.rs links whatever is in .blobs/esp32, or tells you to run make blobs if it is empty. Without that step this crate still builds and tests on its own.

Modules

Section titled “Modules”
  • adapter — Filling in [crate::osi::WifiOsiFuncs].
  • calibration — RF calibration data, persisted across reboots.
  • coex — The nineteen _coex_* entries: Wi-Fi/Bluetooth coexistence.
  • ets_timer — ETSTimer — the blob’s software timers, and esp_timer_get_time.
  • events — The driver’s events: a bounded queue and a task that drains it.
  • interrupts — _set_intr, _clear_intr and _set_isr — the blob’s route to an
  • net — The smoltcp link layer for an associated Wi-Fi station.
  • nvs — nvs_* — the blob’s key/value store, over lib/kvstore.
  • osi — wifi_osi_funcs_t: the table Espressif’s blobs call out through.
  • phy — Bringing the PHY up, and the calibration that goes with it.
  • phy_init — The PHY’s initialisation parameters.
  • scan — Scanning for access points. Step 5.2 of doc/plan-radio.md, issue #67.
  • station — The ESP32 blob backend of [hal::wifi::Station].
  • supplicant — The radio glue for the first-party WPA2 supplicant.
  • tasks — _task_create, _task_create_pinned_to_core and _task_delete — the
  • wifi — esp_wifi_init_internal — handing the Wi-Fi driver its configuration.