# SMA-2 - each inverter is reached through a driver

**Status: for review.** Tests: `test_sma2_driver.py`. Source: SMA-9 report
section 1.1. A pure refactor: no behaviour change for GoodWe, no change to a
command, a log line or a sentence the add-on shows.

Every place that read or steered an inverter used the GoodWe ESPHome entities
directly, so a second make meant touching all of them. `app/drivers.py` now
holds one `Driver` per roster entry (`Inverter.driver`): `configured()`,
`actuator_id()`, `limits()`, `read()`, `write()`, `release()`, `probe()`, and
`link_stale_s`, `batt_bound`, `settle_s`, `brand`, `words`. `GoodWeEsphomeDriver`
makes the same calls in the same order as the code it replaced; its
`release()` is `write(0)`.

**Moved to the driver:** the SoC and power read (`_read_unit`), the write
(`_write_unit`, still under the SAFETY-28 gate, the clamp, shadow mode and the
write budget), the device range (`run_control`, `amain`, the settings panel),
liveness and its window (`has_writer`, `is_live`, `link_note`), the freshness
bound, the status rows' "is a source set" test, rule 2's per-unit range check
and SAFETY-28's census. **Not moved:** the clamp, the gate, the heartbeat and
`command_site_zero()`; stop is still 0 W for every unit, and nothing calls
`release()` yet (SMA-10). `settle_s` and the control constants are not read
from the driver yet either: with only GoodWe they would change nothing.

**The seam is not TCP-shaped.** The census asks each entry's driver for its
actuator id: the setpoint entity for GoodWe, `host:port:unit_id` for a driver
reached over a socket, so two units behind one gateway are two actuators and
one unit named twice is the SAFETY-28 refusal. The driver binds its Home
Assistant on first use by the Controller, so a unit added later is wired too.

**Schema.** `setpoint_entity` is optional per entry (rule 9(d) still requires
it for GoodWe, with the same sentence), beside `driver` (only `goodwe_esphome`),
`host`, `port`, `unit_id`, `maintenance`. The last four are checked for shape
and not read. The Supervisor shape probe was re-run (section K).

**Checked against 23ff9d0:** replay digests and a log of every Home Assistant
call are byte-identical at N=1 and N=2; the TEL-07 announce diff is 0/0/0; a
fake driver beside a GoodWe unit allocates, grades, drops and publishes per
unit; a call site that goes round the seam is caught.