Add proper Zephyr module support with updated HAL for v3/v4 compatibility

[tbitcs]

Summary

This PR introduces first-class support for integrating CryptoAuthLib as a Zephyr module, compatible with Zephyr v3 and v4. It enables seamless integration into modern Zephyr-based applications using CMake and Kconfig, and updates the I2C and SPI HALs to align with Zephyr's evolving include path conventions.

Note: This change breaks compatibility with Zephyr v2.x due to header path and module resolution changes.

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Key Changes

• Added module.yml to enable Zephyr module recognition via west.
• Introduced ATCA_ZEPHYR_SUPPORT CMake option to toggle Zephyr build mode.
• Created zephyr_options.cmake to map CONFIG_ATCA_* Kconfig options to internal CMake flags.
• Refactored HAL sources (I2C, SPI) to use updated Zephyr include paths (zephyr/drivers/...) required in Zephyr ≥ v3.
• Updated top-level CMakeLists to:
• Detect Zephyr toolchain
• Build as a zephyr_library() when enabled
• Export include paths and config headers for Zephyr apps

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Integration Instructions

To include CryptoAuthLib as a Zephyr module:

Option 1: In-tree

Place CryptoAuthLib under modules/lib/cryptoauthlib and it will be automatically detected.

Option 2: Out-of-tree

If using a separate path:

# Add this line before find_package(Zephyr)
set(EXTRA_ZEPHYR_MODULES ${CMAKE_CURRENT_SOURCE_DIR}/../modules/lib/cryptoauthlib)

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Kconfig Support

Once integrated, you can configure CryptoAuthLib via prj.conf using new symbols:

CONFIG_ATCA_HAL_I2C=y
CONFIG_ATCA_CRYPTO_MBEDTLS=y
CONFIG_ATCA_DEVICE_SUPPORT_ECC608=y

These options automatically propagate to the CMake build system, enabling or disabling relevant sources and flags.

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Compatibility Notes

• Verified working on Zephyr v3.5 and v4.1.0
• Breaks backward compatibility with Zephyr v2.x
• No functional changes for non-Zephyr builds (Linux/MPLAB/Harmony remain unaffected)

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Request

If possible, please test against MPLAB Harmony and existing Linux builds to ensure continued compatibility. Feedback and improvements welcome!

Feature branch: https://github.com/BitConcepts/cryptoauthlib/tree/feature/zephyr-module-support-v3-v4

[ElectroInnovator]

Follow-Up Update: I2C Send Function Refactored for Zephyr HAL

This follow-up commit introduces a significant improvement to the I2C HAL layer for Zephyr:

Summary

Refactors hal_i2c_send in hal_zephyr_i2c.c to support word-address-based I2C transfers and improve compatibility with Zephyr's I2C API.

Key Changes

• Updated function signature: uses word_address instead of address for semantic clarity.

• Reads device address from ATCAIfaceCfg, supporting both atcai2c->slave_address and cfg->dev_addr for backward compatibility.

• Implements a two-message I2C transfer:

  • First message transmits the word address.
  • Second (optional) message transmits the data buffer, if data is provided.

• Uses i2c_transfer() instead of i2c_write() for explicit control over transaction flags.

• Sets appropriate I2C flags:

  • I2C_MSG_WRITE
  • I2C_MSG_STOP only after the final message

• Adds parameter validation for both the Zephyr I2C device and the provided config structure.

Motivation

Many I2C peripherals require a separate word address phase before sending data. This update ensures broader device compatibility and aligns our I2C send logic with Zephyr HAL best practices.

Impact

• Increases robustness and configurability of I2C transactions.
• No API change for external callers of hal_i2c_send(), aside from the renamed argument.
• Improves support for devices with word-addressed registers (e.g., EEPROMs, secure elements).