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
• add regression coverage for offline, unknown, and invalid AC-line values

Master already flushes the test child output via exit(), so this PR does not duplicate the stable-branch harness fix.

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

Distinguish supported AC-line status values and handle sentinel or invalid values explicitly.

New Features:

• Report AC-line status 0 as battery power and status 1 as plugged in.

Bug Fixes:

• Reject unknown and invalid AC-line status values with explicit errors instead of treating them as charging or drained.

Tests:

• Add regression tests covering battery power, unknown, and invalid AC-line statuses.

[sourcery-ai]

Reviewer's Guide

The PR replaces the previous fallback AC-line handling with an explicit switch that distinguishes battery power, plugged-in, unknown, and invalid values, and adds ATF regression coverage for the new behavior.

Flow diagram for AC-line status handling

flowchart TD
    A[Read AC line status] --> B{AC line 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 validate and report each supported AC-line status.	Map status 0 to battery-power output and status 1 to plugged-in output. Treat the kernel sentinel -1 as an unknown error. Reject all other AC-line values with an error.	usr.bin/batt/batt.c
Add regression tests for AC-line status handling.	Cover battery-power, unknown-sentinel, and invalid-value cases. Verify exit status, stdout, and relevant stderr diagnostics. Register the three new ATF test cases.	usr.bin/batt/tests/batt_test.c

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[github-actions]

Claude finished @laffer1's task in 1m 45s —— View job

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Review: batt: distinguish AC line status values (#499, merged)

• Gather context
• Review usr.bin/batt/batt.c and usr.bin/batt/tests/batt_test.c
• Post review feedback

No specific question was included in the trigger comment beyond the PR description, so here is a code review of the merged changes per repo review guidelines (correctness, malloc/free symmetry, bounds checking, style(9), security).

Correctness — verified against the kernel side

I cross-checked the new switch in batt.c:110-121 against sys/dev/acpica/acpi_acad.c:

• sc->status is initialized to -1 (acpi_acad_attach, line 179) and only updated from _PSR when the ACPI method returns a valid (non--1) value (acpi_acad_get_status, line 104/109).
• _PSR returns 0 (offline/battery) or 1 (online/AC) per ACPI semantics, matching power_profile_set_state(newstatus ? PERFORMANCE : ECONOMY).

So the new mapping — 0 → "System running on battery power", 1 → "System plugged in", -1 → "AC line status unknown" (exit 1), anything else → "unexpected AC line status value" (exit 1) — is correctly grounded in the actual kernel sentinel/value semantics, not a guess.

Bounds/size checks: The len != sizeof(acline) guard before touching acline is correct and mirrors the existing pattern used for life/time/units elsewhere in the file.

malloc/free: batt.c itself does no dynamic allocation, so symmetry isn't a concern there. In the test harness (batt_test.c), read_fd()'s realloc() result is assigned directly back into data (line 135) — on a hypothetical realloc failure the original buffer would leak — but this is test-only code guarded immediately by ATF_REQUIRE(data != NULL), which aborts the test process, so there's no real-world impact. Not flagging as a required fix.

Style: The new AC-line branch uses an if / else if / else chain (batt.c:105-109) where sibling checks for life/time/units use separate top-level if statements. Purely cosmetic — no functional difference since errx() doesn't return — but worth noting for consistency if this code is touched again.

Security: No injection, overflow, or format-string issues. sysctlbyname usage and output are constant-format printf/puts calls only.

Tests: The new ATF cases (acline_status, battery_power_status, unknown_acline_status, invalid_acline_status) mock all four relevant cases (plugged in, on battery, unknown sentinel, invalid value) and check both exit status and stderr content — good coverage for this change.

Overall: no correctness, memory-safety, or style(9) issues found in the shipped diff.

[Copilot]

🟢 Approval recommended

The change is narrowly scoped, handles the sysctl value domain explicitly, and includes targeted regression coverage for the new behaviors.

Pull request overview

This PR improves usr.bin/batt’s interpretation of the hw.acpi.acline sysctl by distinguishing the supported AC-line status values (0/1), explicitly handling the kernel sentinel -1, and rejecting any other unexpected values; it also adds regression tests to cover the new behavior.

Changes:

• Update batt -t output to report AC-line status 0 as “System running on battery power” and 1 as “System plugged in”.
• Treat AC-line status -1 as “unknown” (exit 1) and reject other values as unexpected (exit 1).
• Add ATF regression tests for battery power, unknown, and invalid AC-line status values.

File summaries

File	Description
usr.bin/batt/batt.c	Switch-based handling of hw.acpi.acline with explicit mapping for 0/1, sentinel -1 error, and default rejection of other values.
usr.bin/batt/tests/batt_test.c	Adds regression test cases for AC-line values 0 (battery), -1 (unknown), and 2 (invalid), and registers them in the test plan.

Review details

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

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