Crate Definition and Metadata

Relevant source files

• Cargo.toml

This page provides a detailed examination of the x86_rtc crate's configuration as defined in Cargo.toml. It covers package metadata, dependency specifications, build configurations, and platform-specific settings that define the crate's behavior and integration requirements.

For implementation details of the RTC driver functionality, see RTC Driver API. For broader dependency analysis including transitive dependencies, see Dependency Analysis.

Package Identification and Core Metadata

The crate is defined with specific metadata that establishes its identity and purpose within the Rust ecosystem.

Crate Metadata Structure

flowchart TD
subgraph External_Links["External_Links"]
    HOMEPAGE["homepage: github.com/arceos-org/arceos"]
    REPOSITORY["repository: github.com/arceos-org/x86_rtc"]
    DOCUMENTATION["documentation: docs.rs/x86_rtc"]
end
subgraph Legal_Metadata["Legal_Metadata"]
    LICENSE["license: GPL-3.0-or-later OR Apache-2.0 OR MulanPSL-2.0"]
end
subgraph Description_Fields["Description_Fields"]
    DESC["description: System RTC Drivers for x86_64"]
    KEYWORDS["keywords: [arceos, x86_64, rtc]"]
    CATEGORIES["categories: [os, hardware-support, no-std]"]
end
subgraph Package_Definition["Package_Definition"]
    NAME["name: x86_rtc"]
    VERSION["version: 0.1.1"]
    EDITION["edition: 2021"]
    AUTHOR["authors: Keyang Hu"]
end

AUTHOR --> LICENSE
DESC --> HOMEPAGE
NAME --> DESC
VERSION --> KEYWORDS

Sources: Cargo.toml(L1 - L12) 

Functional Classification and Discovery

The crate uses specific classification metadata to enable discovery and communicate its intended use cases.

The description field Cargo.toml(L6)  explicitly identifies this as "System Real Time Clock (RTC) Drivers for x86_64 based on CMOS", establishing both the hardware target (x86_64) and the underlying technology (CMOS).

The keywords array Cargo.toml(L11)  includes:

• "arceos" - Associates with the ArceOS operating system project
• "x86_64" - Specifies the target architecture
• "rtc" - Identifies the Real Time Clock functionality

The categories array Cargo.toml(L12)  places the crate in:

• "os" - Operating system development
• "hardware-support" - Hardware abstraction and drivers
• "no-std" - Embedded and kernel development compatibility

Sources: Cargo.toml(L6)  Cargo.toml(L11 - L12) 

Dependency Architecture and Conditional Compilation

The crate implements a two-tier dependency strategy with conditional compilation for platform-specific functionality.

Dependency Configuration Structure

flowchart TD
subgraph Build_Matrix["Build_Matrix"]
    LINUX_TARGET["x86_64-unknown-linux-gnu"]
    BARE_TARGET["x86_64-unknown-none"]
    OTHER_ARCH["Other Architectures"]
end
subgraph Dependency_Purposes["Dependency_Purposes"]
    CFG_PURPOSE["Conditional Compilation Utilities"]
    X86_PURPOSE["Hardware Register Access"]
end
subgraph Platform_Conditional["Platform_Conditional"]
    TARGET_CONDITION["cfg(target_arch = x86_64)"]
    X86_64_DEP["x86_64 = 0.15"]
end
subgraph Unconditional_Dependencies["Unconditional_Dependencies"]
    CFG_IF["cfg-if = 1.0"]
end

CFG_IF --> CFG_PURPOSE
TARGET_CONDITION --> OTHER_ARCH
TARGET_CONDITION --> X86_64_DEP
X86_64_DEP --> BARE_TARGET
X86_64_DEP --> LINUX_TARGET
X86_64_DEP --> X86_PURPOSE

Core Dependencies

cfg-if v1.0 Cargo.toml(L15) 

• Provides conditional compilation utilities
• Included unconditionally across all platforms
• Enables clean platform-specific code organization

Platform-Specific Dependencies

x86_64 v0.15 Cargo.toml(L17 - L18) 

• Only included when target_arch = "x86_64"
• Provides low-level hardware register access
• Essential for CMOS port I/O operations
• Version constraint allows compatible updates within 0.15.x

Sources: Cargo.toml(L14 - L18) 

Licensing and Legal Framework

The crate implements a triple-license strategy providing maximum compatibility across different use cases and legal requirements.

The license specification Cargo.toml(L7)  uses the SPDX format: "GPL-3.0-or-later OR Apache-2.0 OR MulanPSL-2.0"

This allows users to choose from:

• GPL-3.0-or-later: Copyleft license for open-source projects
• Apache-2.0: Permissive license for commercial integration
• MulanPSL-2.0: Chinese-origin permissive license for regional compliance

Sources: Cargo.toml(L7) 

Repository and Documentation Infrastructure

The crate establishes a distributed documentation and development infrastructure across multiple platforms.

The separation between homepage and repository Cargo.toml(L8 - L9)  indicates this crate is part of the larger ArceOS ecosystem while maintaining its own development repository.

Sources: Cargo.toml(L8 - L10) 

Build Configuration and Code Quality

The crate defines specific linting rules to customize Clippy behavior for its use case.

Clippy Configuration Cargo.toml(L20 - L21) 

[lints.clippy]
new_without_default = "allow"

This configuration allows the new_without_default lint, permitting constructor functions named new() without requiring a corresponding Default implementation. This is appropriate for hardware drivers where default initialization may not be meaningful or safe.

Sources: Cargo.toml(L20 - L21) 

Crate Architecture Summary

Complete Crate Definition Flow

flowchart TD
subgraph Ecosystem_Integration["Ecosystem_Integration"]
    ARCEOS_PROJECT["ArceOS Operating System"]
    DOCS_RS["docs.rs Documentation"]
    CARGO_REGISTRY["crates.io Registry"]
end
subgraph Functionality["Functionality"]
    RTC_DRIVER["RTC Driver Implementation"]
    CMOS_ACCESS["CMOS Hardware Interface"]
end
subgraph Platform_Support["Platform_Support"]
    ARCH_CHECK["cfg(target_arch = x86_64)"]
    X86_ONLY["x86_64 hardware required"]
end
subgraph Identity["Identity"]
    CRATE_NAME["x86_rtc"]
    VERSION_NUM["v0.1.1"]
end

ARCEOS_PROJECT --> CARGO_REGISTRY
ARCH_CHECK --> X86_ONLY
CMOS_ACCESS --> DOCS_RS
CRATE_NAME --> ARCH_CHECK
RTC_DRIVER --> ARCEOS_PROJECT
VERSION_NUM --> RTC_DRIVER
X86_ONLY --> CMOS_ACCESS

The Cargo.toml configuration establishes x86_rtc as a specialized hardware driver crate with strict platform requirements, flexible licensing, and integration into the ArceOS ecosystem. The conditional dependency structure ensures the crate only pulls in hardware-specific dependencies when building for compatible targets.

Sources: Cargo.toml(L1 - L22)