batt: distinguish AC line status values

[laffer1]

Summary

• report AC-line value 0 as battery power and value 1 as plugged in
• diagnose the kernel sentinel value -1 as unknown and reject other values
• flush captured stdout in the test child before _exit()
• add regression coverage for offline, unknown, and invalid AC-line values

Testing

• bmake -C usr.bin/batt clean all
• kyua test -k /usr/obj/usr/src/amd64.amd64/usr.bin/batt/tests/Kyuafile (9/9 passed)
• git diff --cached --check -- usr.bin/batt

The repository C-analysis scripts were invoked. Their \.c$ filter skipped clang-tidy and Splint, so both were also run manually. Splint cannot parse the current system headers; clang-tidy/cppcheck reported pre-existing diagnostics in batt and its test harness, with no diagnostic specific to the new AC-line switch.

AI-Assisted-by: GPT-5.6 (Codex)

Summary by Sourcery

Handle AC-line status values explicitly and add regression coverage for valid, unknown, and invalid states.

New Features:

• Distinguish battery-powered, plugged-in, unknown, and invalid AC-line status values in batt output.

Bug Fixes:

• Treat the kernel AC-line sentinel value -1 as an explicit error instead of reporting a charging or drained state.

Enhancements:

• Flush captured child-process stdout before exiting to ensure test output is preserved.

Tests:

• Add regression coverage for battery-power, unknown, and invalid AC-line statuses.

[sourcery-ai]

Reviewer's Guide

The PR replaces ambiguous AC-line handling with explicit 0/1/-1/invalid classification and adds ATF regression tests for each new behavior, while flushing child stdout to ensure captured output is deterministic.

Flow diagram for AC-line status classification

flowchart TD
    A[Read AC line status] --> B{acline value}
    B -->|0| C[Print System running on battery power]
    B -->|1| D[Print System plugged in]
    B -->|-1| E[Exit with AC line status unknown]
    B -->|other| F[Exit with unexpected AC line status value]

Loading

File-Level Changes

Change	Details	Files
Explicitly classify every AC-line sysctl value and fail on unknown or invalid states.	Map 0 to battery-power output and 1 to plugged-in output. Treat -1 as an unknown-state error and reject all other values. Preserve existing size and availability validation before classification.	usr.bin/batt/batt.c
Expand regression coverage for AC-line state handling and make child-process output capture reliable.	Flush captured stdout before exiting the test child. Add tests for offline, kernel-sentinel unknown, and invalid AC-line values, including exit status and diagnostics. Register the new tests in the ATF test program.	usr.bin/batt/tests/batt_test.c

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[Copilot]

🟢 Approval recommended

The behavior change is small, consistent with kernel semantics (including -1), and is covered by targeted regression tests.

Pull request overview

Updates batt(1) to handle hw.acpi.acline values explicitly, distinguishing battery vs plugged-in states, treating the kernel sentinel -1 as “unknown”, and rejecting other unexpected values; also strengthens the test harness to reliably capture child stdout output.

Changes:

• Replace the previous “non-1” fallback message with a switch over AC-line status (0=battery, 1=plugged in, -1=unknown/error, other=error).
• Flush child-process stdout in the test runner before _exit() so buffered output (notably non-newline outputs) is not lost.
• Add regression tests covering offline (0), unknown (-1), and invalid (2) AC-line values.

File summaries

File	Description
usr.bin/batt/batt.c	Implements explicit AC-line status handling via switch (acline) including unknown (-1) and invalid-value rejection.
usr.bin/batt/tests/batt_test.c	Ensures stdout is flushed before _exit() and adds test cases for battery/unknown/invalid AC-line status behavior.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite

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