# Re: \[PATCH net-next v2 00/14\] dpll: add a simulated DPLL device driver

- From: Jiri Pirko \<jiri@resnulli.us\>
- Date: 2026-11-06 12:27:30 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/11/17878148
- Thread: https://ratatoskr.run/netdev/2026/11/17871508/t.md

```text
Thu, Nov 05, 2026 at 04:18:38PM +0100, poros@redhat.com wrote:
>The DPLL subsystem has no in-tree driver that can run without real
>hardware, so core changes and userspace tooling are hard to exercise in
>CI, and the pin-on-pin and reference sync paths see almost no coverage
>outside the vendors' labs. This series adds dpllsim, a simulated DPLL
>device driver, together with selftests that run against it.
>
>The driver is controlled through configfs, following gpio-sim. Writing a
>clock ID into a device directory and setting "live" to 1 registers a
>DPLL device with the core. Pins are directories under pins/ with their
>type, frequency, direction and priority as attributes, and all of them
>are registered when the device goes live. The split between creating
>the configuration and going live keeps the register and unregister
>paths reachable from userspace, so they can be exercised repeatedly
>without reloading the module. Nothing in the simulator is a stable ABI.
>
>The patches follow the shape of the zl3073x introduction. The
>driver starts with the device alone, then gains pins and the static pin
>operations one at a time (state, priority, frequency, phase adjustment),
>and every feature patch is followed by the selftest that covers it. The
>last two patches add concurrency stress tests and reference tracker
>leak tests for the lifecycle paths.
>
>The simulation loop (lock state machine, phase and frequency
>measurements, monitoring features), the topology features (MUX pin
>hierarchies, reference sync, media failure injection), netdevsim
>integration and device mode setting follow in two further series once
>this one is in, to stay within the 15 patch limit.
>
>The driver and the selftests were developed with an LLM coding
>assistant (Claude Code) working under my direction. I chose the
>configfs design, the split into one feature per patch and the test
>scenarios, and I reviewed every line. The assistant wrote most of the
>code and the first drafts of the changelogs, and it found and fixed
>bugs by running the suite on the lab host. The series then went
>through several rounds of an LLM based patch reviewer whose findings
>were fixed, and through a mutation test in which deliberately broken
>driver and core code was caught by the tests.
>
>The selftests live in tools/testing/selftests/drivers/net/dpll and run
>with "make -C tools/testing/selftests TARGETS=drivers/net/dpll
>run_tests". By default they create dpllsim devices; with
>DPLL_DEV_ID=<id> the basic and feature scripts run against an existing
>device instead, so the same suite exercises real hardware. The whole
>suite was run through the kselftest runner on an ice E810 host with
>CONFIG_KASAN, CONFIG_PROVE_LOCKING and CONFIG_DPLL_REFCNT_TRACKER
>enabled, against the simulator and, with DPLL_DEV_ID, against the ice
>DPLL, where the tests that need a simulator skip and the pin state and
>priorities of the hardware are left as they were. All pass with no
>warnings in dmesg.
>

set-
Acked-by: Jiri Pirko <redacted>
```