Course Structure. SPI Device Driver Development

Linux SPI Device Driver Development: Live Online Course

Module 1: SPI Protocol Deep Dive (Sessions 1-4)

The goal is to establish a solid theoretical foundation of the SPI protocol before touching any code.

Session	Topic	Key Concepts & Activities
1	Introduction to SPI	The need for SPI, its advantages (simplicity, high speed) and disadvantages. Comparison with I2C and UART. Master-Slave architecture.
2	SPI Signals and Timing	Detailed analysis of the four wires: SCLK (Clock), MOSI (Master Out Slave In), MISO (Master In Slave Out), SS/CS (Slave Select/Chip Select). Role of Chip Select.
3	SPI Modes (Clock Polarity & Phase)	Understanding CPOL and CPHA (Mode 0, 1, 2, 3). How they dictate data sampling and clock edge. Clock frequency and duty cycle considerations.
4	Data Frames, Word Size, and Transactions	Analyzing data frames (typically 8-bit). Concepts of word size and transactions. Handling multiple slaves and bus sharing.

Module 2: Linux SPI Subsystem Architecture (Sessions 5-8)

This module introduces the key Linux kernel structures and APIs for handling SPI.

Session	Topic	Key Concepts & Activities
5	The Linux Device Model & SPI	Review of bus-device-driver model. Introduction to the SPI Bus Type. The SPI Master (Controller) and SPI Slave (Device) roles in the kernel.
6	SPI Subsystem Structures	Detailed look at the core structures: struct spi_master, struct spi_device, and struct spi_driver. How they interconnect.
7	The spi_message & spi_transfer	Understanding the data structures used for communication. spi_message (the container) vs. spi_transfer (the data units). Full-duplex communication.
8	SPI Communication APIs	Core functions: spi_sync(), spi_async(), spi_write(), spi_read(). Choosing the right API for different scenarios (blocking vs. non-blocking).

Module 3: Implementing the SPI Device Driver - The Core (Sessions 9-14)

Hands-on implementation of the device driver skeleton, focusing on registration and basic I/O. We will target a common SPI device, like an SPI Flash memory or an accelerometer.

Session	Topic	Key Concepts & Activities
9	Driver Registration and Probe	Creating the struct spi_driver. Implementing the probe() and remove() functions. Accessing device-specific configuration from Device Tree.
10	Accessing Device Tree Data	Reviewing Device Tree (DT) basics for SPI. Reading properties like chip select, mode, and max speed from the DT node using of_get_xxx() APIs.
11	Setting Up Character Device Interface	Integrating the SPI driver with the familiar character device (cdev) interface. Storing the struct spi_device reference in the character device private data.
12	Implementing read() and write()	Mapping user-space read/write calls to kernel-space spi_sync() calls. Handling data transfer buffers and length checks.
13	Handling Device Configuration (IOCTL)	Using ioctl() to allow user-space to configure device-specific settings (e.g., turning on/off a feature, changing sample rate). Implementing the unlocked_ioctl method.
14	Practical: Building and Testing I/O	Lab Session: Compile and load the basic driver. Use user-space tools (dd, custom test program) to verify basic read/write functionality with the target device.

Module 4: Advanced Driver Techniques (Sessions 15-18)

Focus on production-level driver features: error handling, power management, and interrupt integration.

Session	Topic	Key Concepts & Activities
15	Error Handling and Resource Cleanup	Implementing robust error paths in probe() and remove(). Proper resource deallocation (cdev, memory, IRQ). Handling SPI transfer errors.
16	Integrating Interrupts (IRQ)	Handling device-initiated interrupts. Registering and writing a Linux IRQ handler (request_irq()). Using interrupt context vs. process context (Bottom Halves: Tasklets or Workqueues).
17	Handling Multi-Word Transfers	Implementing sequential transfers (e.g., command + address + data) using multiple spi_transfer structures within a single spi_message.
18	Power Management (PM) Hooks	Implementing the struct dev_pm_ops for the SPI device driver. Handling suspend and resume calls to save and restore the device state.

Module 5: Debugging, Best Practices, and Review (Sessions 19-20)

Final sessions dedicated to debugging skills and best practices for driver maintenance.

Session	Topic	Key Concepts & Activities
19	Debugging SPI Drivers	Essential debugging techniques: printk() usage and log levels. Using the dynamic_debug feature. ftrace and hardware logic analyzer usage for verifying SPI signals.
20	Code Review & Next Steps	Reviewing common SPI driver issues (endianness, race conditions). Best practices for upstreaming patches. Final Q&A and Project Review.