D675 - Sysctl knobs split between the platform and the profile

Status: decided Date: 2026-09-10

A knob whose value is published for the architecture answers on every machine; a knob that carries one hardware unit's firmware values comes verbatim from the machine profile; live state, and knobs the hardware itself refuses, stay refused. A profile knob on a machine that carries no value refuses rather than answering empty.

Why: a published constant is the same on every machine, while a kernel banner or a model string belongs to one unit, and composing the banner from the firmware version would invent its revision and build date. Available-page counts are one moment of a memory model that is not orbistoun's. An empty answer on an unset machine would score knobs it knows nothing about as answered.

Rejected:

• Answering empty for every unset string knob: claims a value exists where nothing is known.
• Transcribing live values such as available pages: a constant posing as a measurement of this run.
• Composing the banner from the firmware version: invents the revision and the date.