Firmware v2.12.0

A serial console could reboot the board by accident.

Firmware v2.12.0, 9 September 2026. Every item below is the repository's own changelog entry, taken apart; the whole entry is a click away under each one.

Fixed¶

A serial console could reboot the board by accident. The kernel boots with console=ttyS0 and a BREAK on that line triggers SysRq, with the next byte taken as the command.
The whole entry

USB-serial adapters assert BREAK whenever a port is opened, closed or reconfigured, and nothing guarded it. The kernel's own help for MAGIC_SYSRQ_SERIAL describes the hazard exactly: "a disconnected TTL level serial which can generate some garbage that can lead to spurious false sysrq detects."

The first instinct was to mask the dangerous commands off. That was the wrong trade: this board has no watchdog, so a serial reset is the only remedy short of walking to the rack, and it is worth keeping.

So the trigger is guarded rather than the commands removed. MAGIC_SYSRQ_SERIAL_SEQUENCE="sysrq" means a BREAK on its own now does nothing; the sequence must follow it before any command is accepted. Garbage cannot produce that and a person typing it means it. The full command set stays available:
```
BREAK, then "sysrq", then the key
  b  reboot        o  power off      s  sync
  w  blocked tasks m  memory         t  all tasks
```
S00sysrq sets the runtime value to match, so the intent is visible in the init scripts and not only in a kernel config.

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