#28: Terminate ZPC upon USB/Serial connection loss

[Márk Mihalik | SiliconLabs (silabs-MarkM)]

Issue

• ZPC does not terminate upon SAPI controller device poweroff #28
• JIRA: ZWAVE_SDK-2336

Closes: #28

Change

Feature:

• Exit ZPC when the NCP serial device is unplugged (hangup / fatal serial errno → RX kill switch)

Bugfix:

• ACK timeouts reconnect via zwapi_connection_restart() again (serial reopen or IP reconnect); they do not mark the serial port lost
• Exhausted TX retries fail the frame only; they do not brick a live SerialAPI
• mark_lost is a no-op on IP (serial never opened); do not close the serial fd from the TX thread
• Detect POLLHUP even when the RX poll queue still has work
• CMake skips command-class dirs with no CMakeLists.txt (leftover Time CC tree)

Not in this PR:

• IP exit(1) on recv/send (pre-existing)

Checklist

• Pull request template has been filled out correctly
• ./ci/scripts/clang-tidy.sh check has been run locally (see CONTRIBUTING.md)
• Documentation has been updated if necessary
• A Contribution License Agreement has been established between Silicon Labs (@SiliconLabs) and author's company (matching email domain)

[siliconlabsdevops-svc-devops]

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