Dependencies and Platform Support

Relevant source files

• Cargo.lock
• Cargo.toml

This document provides a comprehensive analysis of the x86_rtc crate's dependencies, platform requirements, and architecture-specific constraints. It covers both direct and transitive dependencies, explains the conditional compilation strategy, and documents the specific platform support matrix.

For detailed crate configuration and metadata information, see Crate Definition and Metadata. For implementation-specific dependency usage, see Implementation.

Dependency Architecture Overview

The x86_rtc crate follows a minimal dependency strategy, with only two direct dependencies and a small transitive dependency tree focused on hardware abstraction and conditional compilation.

flowchart TD
subgraph subGraph3["Conditional Compilation"]
    ARCH_GATE["target_arch = x86_64"]
end
subgraph subGraph2["Transitive Dependencies"]
    BIT_FIELD["bit_field v0.10.2"]
    BITFLAGS["bitflags v2.6.0"]
    RUSTVERSION["rustversion v1.0.19"]
    VOLATILE["volatile v0.4.6"]
end
subgraph subGraph1["Direct Dependencies"]
    CFG_IF["cfg-if v1.0"]
    X86_64["x86_64 v0.15"]
end
subgraph subGraph0["x86_rtc Crate"]
    ROOT["x86_rtc v0.1.1"]
end

ARCH_GATE --> X86_64
ROOT --> ARCH_GATE
ROOT --> CFG_IF

Sources: Cargo.toml(L14 - L18)  Cargo.lock(L48 - L53) 

Direct Dependencies

cfg-if v1.0

The cfg-if crate provides ergonomic conditional compilation macros, essential for platform-specific code paths in the RTC driver.

Sources: Cargo.toml(L15)  Cargo.lock(L18 - L21) 

x86_64 v0.15 (Conditional)

The x86_64 crate is the primary hardware abstraction layer, providing safe access to x86_64-specific instructions and memory-mapped I/O operations required for CMOS interaction.

Sources: Cargo.toml(L17 - L18)  Cargo.lock(L36 - L45) 

Transitive Dependencies

The x86_64 crate brings in four transitive dependencies that provide low-level hardware access capabilities:

Hardware Access Stack

flowchart TD
subgraph subGraph4["CMOS Hardware Interface"]
    PORT_ACCESS["I/O Port Operations"]
    REGISTER_FIELDS["CMOS Register Fields"]
    MEMORY_SAFETY["Volatile Memory Access"]
end
subgraph subGraph3["Hardware Abstraction Layers"]
    X86_CRATE["x86_64 crate"]
    subgraph subGraph2["Build-time Utilities"]
        RUSTVERSION_DEP["rustversion v1.0.19"]
    end
    subgraph subGraph1["Memory Safety"]
        VOLATILE_DEP["volatile v0.4.6"]
    end
    subgraph subGraph0["Register Management"]
        BIT_FIELD_DEP["bit_field v0.10.2"]
        BITFLAGS_DEP["bitflags v2.6.0"]
    end
end

BITFLAGS_DEP --> REGISTER_FIELDS
BIT_FIELD_DEP --> REGISTER_FIELDS
VOLATILE_DEP --> MEMORY_SAFETY
VOLATILE_DEP --> PORT_ACCESS
X86_CRATE --> BITFLAGS_DEP
X86_CRATE --> BIT_FIELD_DEP
X86_CRATE --> RUSTVERSION_DEP
X86_CRATE --> VOLATILE_DEP

Sources: Cargo.lock(L40 - L44) 

Dependency Details

Sources: Cargo.lock(L6 - L45) 

Platform Requirements

Architecture Specificity

The x86_rtc crate is exclusively designed for x86_64 architecture due to its dependence on CMOS hardware implementation specific to x86-compatible systems.

Sources: Cargo.toml(L17)  Cargo.toml(L11) 

no_std Compatibility

The crate is designed for no_std environments, making it suitable for:

• Operating system kernels
• Embedded systems
• Bootloaders
• Hypervisors

Sources: Cargo.toml(L12) 

Conditional Compilation Strategy

The crate employs a sophisticated conditional compilation strategy to ensure platform safety and optimal builds.

flowchart TD
subgraph subGraph2["Compilation Decision Tree"]
    START["Build Process"]
    ARCH_CHECK["target_arch == x86_64?"]
    CFG_IF_USAGE["cfg-if macro usage"]
    subgraph subGraph1["Non-x86_64 Path"]
        EXCLUDE_X86["Exclude x86_64 crate"]
        COMPILE_ERROR["Compilation fails"]
        NO_IMPL["No RTC implementation"]
    end
    subgraph subGraph0["x86_64 Path"]
        INCLUDE_X86["Include x86_64 crate"]
        HARDWARE_ACCESS["Enable hardware access"]
        CMOS_INTERFACE["Compile CMOS interface"]
    end
end

ARCH_CHECK --> EXCLUDE_X86
ARCH_CHECK --> INCLUDE_X86
COMPILE_ERROR --> NO_IMPL
EXCLUDE_X86 --> COMPILE_ERROR
HARDWARE_ACCESS --> CMOS_INTERFACE
INCLUDE_X86 --> HARDWARE_ACCESS
START --> ARCH_CHECK
START --> CFG_IF_USAGE

Sources: Cargo.toml(L17 - L18) 

Conditional Dependency Declaration

The conditional dependency syntax in Cargo.toml ensures that the x86_64 crate and its transitive dependencies are only included when building for compatible targets:

[target.'cfg(target_arch = "x86_64")'.dependencies]
x86_64 = "0.15"

Sources: Cargo.toml(L17 - L18) 

Supported Build Targets

Primary Targets

Unsupported Architectures

The following architectures are explicitly unsupported due to hardware constraints:

• ARM64 (aarch64)
• ARM32 (arm)
• RISC-V (riscv64)
• WebAssembly (wasm32)

Sources: Cargo.toml(L11)  Cargo.toml(L17) 

Version Constraints and Compatibility

The crate maintains conservative version constraints to ensure stability:

Direct Dependency Versions

Transitive Version Resolution

The locked dependency versions provide a stable foundation:

• All transitive dependencies use semantic versioning
• Version locks prevent unexpected breaking changes
• Regular updates maintain security and compatibility

Sources: Cargo.toml(L15)  Cargo.toml(L18)  Cargo.lock(L1 - L54)