NetBSD Implementation (Sysmon)

Relevant source files

The following files were used as context for generating this wiki page:

• src/platform/netbsd/device.rs
• src/platform/mod.rs
• src/platform/traits.rs
• src/lib.rs
• Cargo.toml
• CHANGELOG.md

The NetBSD implementation of the battery crate provides access to battery information via the NetBSD envsys (Environmental Systems) framework and the sysmon device. It specifically supports the acpibat driver, which exposes battery metrics such as charge state, voltage, and capacity through ioctl calls and Property List (plist) data structures.

This module translates platform-specific dictionary values into a unified SI measurement units format. It enables the crate to support NetBSD alongside other Unix-like systems such as FreeBSD and Linux.

Sources: src/platform/netbsd/device.rs:18-20, src/lib.rs:8-13, CHANGELOG.md:46-48

Architecture and Data Flow

The NetBSD implementation follows a two-stage data processing pipeline. First, it extracts raw data from the system using the envsys interface into an intermediate EnvSysDevice. Second, it transforms that raw data into a SysMonDevice that implements the standard BatteryDevice trait used throughout the library.

Data Extraction Pipeline

The implementation relies on the plist crate to parse dictionary-based responses from the NetBSD kernel. The EnvSysDevice struct maps specific ACPI battery (acpibat) sensor indices to battery properties.

Key Components

EnvSysDevice

This internal struct acts as the raw data container. It validates that the hardware device is an acpibat driver and that the device class is indeed a battery. It handles the extraction of current, full, and design capacities, as well as charge/discharge rates.

Field	Description	Source Index
name	The device name (must start with acpibat)	N/A
energy	Current charge level	ACPIBAT_CAPACITY
energy_full	Last full capacity	ACPIBAT_LFCCAPACITY
energy_full_design	Design capacity	ACPIBAT_DCAPACITY
charge_rate	Current charging rate	ACPIBAT_CHARGERATE
discharge_rate	Current discharging rate	ACPIBAT_DISCHARGERATE
charging	Charging state flag	ACPIBAT_CHARGING

Sources: src/platform/netbsd/device.rs:25-46, src/platform/netbsd/device.rs:51-100

SysMonDevice

This is the primary implementation of the BatteryDevice trait for NetBSD. It stores converted SI units using the uom crate.

Unit Conversion Logic

NetBSD can report battery metrics in different units depending on the hardware. The implementation specifically handles "Ampere hour" and "Watt hour" for capacity, and "Ampere" or "Watts" for power rates.

1. Capacity Conversion: If units are in Ampere hours, the value is multiplied by the design voltage to derive Energy (Watt-hours).
2. Rate Conversion: If power is reported in Amperes, it is multiplied by the current voltage to determine the Energy Rate in Watts.
3. State Determination: The state is derived by comparing current energy to full energy (setting State::Full if equal or greater) or checking the charging flag (1 for Charging, 0 for Discharging).

Sources: src/platform/netbsd/device.rs:141-175

Platform Integration

The NetBSD implementation is conditionally compiled and aliased to the standard Manager, Iterator, and Device types when the target OS is netbsd.

// src/platform/mod.rs:31-35
 } else if #[cfg(target_os = "netbsd")] {
    mod netbsd;

    pub type Manager = netbsd::SysMonManager;
    pub type Iterator = netbsd::SysMonIterator;
    pub type Device = netbsd::SysMonDevice;
}

The Cargo.toml specifies required dependencies for this platform, including nix with ioctl and mman features, and the plist crate for data parsing.

Sources: src/platform/mod.rs:31-35, Cargo.toml:53-56

Implementation Limitations

As noted in the source code, the NetBSD implementation does not provide all possible battery metadata. The following fields are currently unsupported and return None or Unknown:

• Technology: Always returns Technology::Unknown.
• Temperature: Not available (returns None).
• Vendor/Model/Serial: Not exposed by the current acpibat sysmon interface (returns None).
• Cycle Count: Not available (returns None).

Sources: src/platform/netbsd/device.rs:188-251

Summary

The NetBSD Implementation (Sysmon) provides a robust bridge between the NetBSD envsys kernel interface and the rust-battery unified API. By parsing kernel plists and performing unit conversions from Amperes/Ampere-hours to SI Watts/Joules, it ensures consistent battery monitoring capabilities for NetBSD users.