This course is designed to show experienced programmers how to develop device drivers for embedded Linux systems, and give them a basic understanding and familiarity with the Linux kernel.
Developing Embedded Linux Device Drivers (LFD435)
Course Overview
Developing Embedded Linux Device Drivers is designed to show experienced programmers how to develop device drivers for Linux systems, and give them a basic understanding and familiarity with the Linux kernel.
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Upon mastering this material, you will be familiar with the different kinds of device drivers used under Linux, and have an introduction to many of the appropriate APIs to be used when writing a device driver. The labs for illustrating these concepts will all be performed on ARM hardware in order to get developers familiar with cross-compiling and developing drivers for an embedded target. The included development kit (yours to keep) will be used to illustrate testing kernel drivers using TFTP and NFSroot techniques.
While we will discuss kernel internals and algorithms we will examine deeply only the functions which are normally used in device drivers. More details on things such as scheduling, memory management, etc., belong more properly in a different, kernel-focused course.
Schedule
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Course Outline
- Introduction
- Objectives
- Who You Are
- The Linux Foundation
- Linux Foundation Training
- Certification Programs and Digital Badging
- Linux Distributions
- Preparing Your System
- Things change in Linux
- Documentation and Links
- Course Registration
- Preliminaries
- Procedures
- Kernel Versions
- Kernel Sources and Use of git
- Hardware
- Staging Tree
- How to Work in OSS Projects **
- Overview on How to Contribute Properly
- Stay Close to Mainline for Security and Quality
- Study and Understand the Project DNA
- Figure Out What Itch You Want to Scratch
- Identify Maintainers and Their Work Flows and Methods
- Get Early Input and Work in the Open
- Contribute Incremental Bits, Not Large Code Dumps
- Leave Your Ego at the Door: Don’t Be Thin-Skinned
- Be Patient, Develop Long Term Relationships, Be Helpful
- Cross-Development Toolchain
- The Compiler Triplet
- Built-in Linux Distribution Cross Compiler
- Linaro
- CodeSourcery
- crosstool-ng
- Buildroot
- OpenEmbedded
- Yocto Project
- Labs
- Basic Target Development Board Setup
- Objectives of the Lab
- Labs
- Booting a Target Development Board over Ethernet
- An easier way to develop
- Objectives of the Lab
- Labs
- Kernel Configuration, Compilation, Booting
- Configuring the Kernel for the Development Board
- Labs
- Device Drivers
- Types of Devices
- Mechanism vs. Policy
- Avoiding Binary Blobs
- Power Management
- How Applications Use Device Drivers
- Walking Through a System Call Accessing a Device
- Error Numbers
- printk()
- devres: Managed Device Resources
- Labs
- Modules and Device Drivers
- The module_driver() Macros
- Modules and Hot Plug
- Labs
- Memory Management and Allocation
- Virtual and Physical Memory
- Memory Zones
- Page Tables
- kmalloc()
- __get_free_pages()
- vmalloc()
- Slabs and Cache Allocations
- Labs
- Character Devices
- Device Nodes
- Major and Minor Numbers
- Reserving Major/Minor Numbers
- Accessing the Device Node
- Registering the Device
- udev
- dev_printk() and Associates
- file_operations Structure
- Driver Entry Points
- The file and inode Structures
- Miscellaneous Character Drivers
- Labs
- Kernel Features
- Components of the Kernel
- User-Space vs. Kernel-Space
- What are System Calls?
- Available System Calls
- Scheduling Algorithms and Task Structures
- Process Context
- Labs
- Transferring Between User and Kernel Space
- Transferring Between Spaces
- put(get)_user() and copy_to(from)_user()
- Direct Transfer: Kernel I/O and Memory Mapping
- Kernel I/O
- Mapping User Pages
- Memory Mapping
- User-Space Functions for mmap()
- Driver Entry Point for mmap()
- Accessing Files from the Kernel
- Labs
- Platform Drivers
- What are Platform Drivers?
- Main Data Structures
- Registering Platform Devices
- An Example
- Hardcoded Platform Data
- The New Way: Device Trees
- Labs
- Device Trees
- What are Device Trees?
- What Device Trees Do and What They Do Not Do
- Device Tree Syntax
- Device Tree Walk Through
- Device Tree Bindings
- Device Tree support in Boot Loaders
- Using Device Tree Data in Drivers
- Coexistence and Conversion of Old Drivers
- Labs
- Interrupts and Exceptions
- What are Interrupts and Exceptions?
- Exceptions
- Asynchronous Interrupts
- MSI
- Enabling/Disabling Interrupts
- What You Cannot Do at Interrupt Time
- IRQ Data Structures
- Installing an Interrupt Handler
- Labs
- Timing Measurements
- Kinds of Timing Measurements
- Jiffies
- Getting the Current Time
- Clock Sources
- Real Time Clock
- Programmable Interval Timer
- Time Stamp Counter
- HPET
- Going Tickless
- Kernel Timers
- Inserting Delays
- What are Kernel Timers?
- Low Resolution Timer Functions
- Low Resolution Timer Implementation
- High Resolution Timers
- Using High Resolution Timers
- Labs
- ioctls
- What are ioctls?
- Driver Entry point for ioctls
- Defining ioctls
- Labs
- Unified Device Model and sysfs
- Unified Device Model
- Basic Structures
- Real Devices
- sysfs
- kset and kobject examples
- Labs
- Firmware
- What is Firmware?
- Loading Firmware
- Labs
- Sleeping and Wait Queues
- What are Wait Queues?
- Going to Sleep and Waking Up
- Going to Sleep Details
- Exclusive Sleeping
- Waking Up Details
- Polling
- Labs
- Interrupt Handling: Deferrable Functions and User Drivers
- Top and Bottom Halves
- Softirqs
- Tasklets
- Work Queues
- New Work Queue API
- Creating Kernel Threads
- Threaded Interrupt Handlers
- Interrupt Handling in User-Space
- Labs
- Hardware I/O
- Memory Barriers
- Allocating and Mapping I/O Memory
- Accessing I/O Memory
- Direct Memory Access (DMA)**
- What is DMA?
- DMA Directly to User
- DMA and Interrupts
- DMA Memory Constraints
- DMA Masks
- DMA API
- DMA Pools
- Scatter/Gather Mappings
- Labs
- Memory Technology Devices (Flash Memory Filesystems)
- What are MTD Devices?
- NAND vs. NOR vs. eMMC
- Driver and User Modules
- Flash Filesystems
- Labs
- USB Drivers
- What is USB?
- USB Topology
- Terminology
- Endpoints
- Descriptors
- USB Device Classes
- USB Support in Linux
- Registering USB Device Drivers
- Moving Data
- Example of a USB Driver
- Labs
- Closing and Evaluation Survey
- Evaluation Survey
Appendices
- Booting the Target Development Board from uSD
- Objectives of the Lab
- Labs
- Kernel Architecture I
- UNIX and Linux **
- Monolithic and Micro Kernels
- Object-Oriented Methods
- Main Kernel Tasks
- User-Space and Kernel-Space
- Kernel Programming Preview
- Task Structure
- Memory Allocation
- Transferring Data between User and Kernel Spaces
- Linked Lists
- Jiffies
- Labs
- Modules
- What are Modules?
- A Trivial Example
- Compiling Modules
- Modules vs Built-in
- Module Utilities
- Automatic Loading/Unloading of Modules
- Module Usage Count
- Module Licensing
- Exporting Symbols
- Resolving Symbols **
- {D.11Labs
- Kernel Architecture II
- Processes, Threads, and Tasks
- Kernel Preemption
- Real Time Preemption Patch
- Labs
- Kernel Configuration and Compilation
- Installation and Layout of the Kernel Source
- Kernel Browsers
- Kernel Configuration Files
- Kernel Building and Makefiles
- initrd and initramfs
- Labs
- Kernel Style and General Considerations
- Coding Style
- Using Generic Kernel Routines and Methods
- Making a Kernel Patch
- sparse
- Using likely() and unlikely()
- Writing Portable Code, CPU, 32/64-bit, Endianness
- Writing for SMP
- Writing for High Memory Systems
- Power Management
- Keeping Security in Mind
- {G.11Labs
- Race Conditions and Synchronization Methods
- Concurrency and Synchronization Methods
- Atomic Operations
- Bit Operations
- Spinlocks
- Seqlocks
- Disabling Preemption
- Mutexes
- Semaphores
- Completion Functions
- Read-Copy-Update (RCU)
- {H.11Reference Counts
- {H.12Labs
- Memory Addressing
- Virtual Memory Management
- Systems With and Without MMU and the TLB
- Memory Addresses
- High and Low Memory
- Memory Zones
- Special Device Nodes
- NUMA
- Paging
- Page Tables
- page structure
- {I.11Labs
- Memory Allocation
- Requesting and Releasing Pages
- Buddy System
- Slabs and Cache Allocations
- Memory Pools
- kmalloc()
- vmalloc()
- Early Allocations and bootmem()
- Memory Defragmentation
- Labs
** These sections may be considered in part or in whole as optional. They contain either background reference material, specialized topics, or advanced subjects. The instructor may choose to cover or not cover them depending on classroom experience and time constraints.
Prerequisites
Knowledge of basic kernel interfaces and methods such as how to write, compile, load and unload modules, use synchronization primitives, and the basics of memory allocation and management, such as is provided by LFD420 (Kernel Internals and Development). Pre-class preparation material will be provided before class.
At a Glance
Delivery Method
Live (Classroom)
Includes
- 4 days of Instructor-led class time
- Hands-on Labs & Assignments
- Resources & Course Manual
- Certificate of Completion
- Free Chromebook
Experience Level
Intermediate
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