Developing Linux Device Drivers

Course category
Course code
EL-504
Duration
5 days
Course date
Price exc VAT
£2500.00

Implementing Linux on custom hardware will, in most cases, require you to write device drivers.

This course will show you how to create Linux Device Drivers and that work with a recent version of the Linux kernel that are able to handle hardware events and present a standard interface to applications.

This course presents a detailed view of Linux device drivers with an emphasis on topics specific to embedded environments: cross compilation; remote debugging and direct hardware manipulation. It uses a combination of theory and practice, using a development board with an ARM core.

No prior knowledge of Linux device drivers is assumed, making it ideal for engineers porting from code from an RTOS to Linux.

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Course objectives:

  • Demonstrate how to write drivers for custom hardware
  • Provide insight into porting drivers from an RTOS to Linux, e.g. the separation between application and kernel code
  • Describe the development tools needed, including debug strategies
  • Examine the way drivers can affect real-time behaviour and best practice to avoid scheduling latencies

Delegates will learn:

  • How to write kernel modules
  • How to create robust drivers using mutexes and spinlocks to serialise access to shared data
  • How to debug kernel code running on a remote embedded target
  • Working with GPIO
  • How to handle interrupts, including deferred processing using tasklets and work queues
  • How to access hardware resources
  • The details of memory management and memory mapping techniques
  • An introduction to writing a USB driver

Pre-requisites:

  • Good ‘C’ programming skills
  • General knowledge of an RTOS or embedded operating systems
  • Knowledge of Linux or Unix is essential
  • Some knowledge of Linux user space is an advantage
  • Able to use a command line interface

Who should attend:

Software engineers who are developing applications for embedded or real-time Linux.

Engineers wishing to assess the suitability of Linux for their next application.

Duration:

Five days.

Course material:

  •  Student workbook

Course workshop

During the lab sessions, students will write several fully-function device drivers, including a FIFO, a RAM disk and a loop-back network interface. All exercises are developed and cross-compiled on a PC running Linux.

The target platform will be the BeagleBone Black, which uses an ARM Cortex-A8. This will help delegates understand the issues encountered when writing for embedded platforms.

Writing Kernel Modules

  • Structure of a kernel module
  • Compiling and loading modules

Introduction to character device drivers

  • Major and minor numbers
  • Basic operations – open, read, write and release
  • Example driver based on a fifo

Debugging Kernel code and device drivers

  • Kernel oops messages
  • Debugging with gdb and kgdb

The Linux driver model

  • sysfs and the /sys directory
  • Adding device classes and class attributes

Task synchronisation

  • Putting tasks to sleep using wait queues
  • Re-entrancy issues
  • Mutexes, semaphores and spinlocks

Device Tree

  • An introduction to device tree and it's usage
  • Creating an example platform driver to bridge the Device Tree – Kernel divide

Input and output

  • Interfacing with the real world
  • Accessing memory and i/o mapped resources

Time

  • Delays and sleeps
  • Using kernel timers.

Interrupts

  • Installing an interrupt handler; interrupt context and process context
  • Deferred processing using a bottom half or tasklet.

Memory management

  • Allocating memory by pages and bytes
  • Slab caches
  • Techniques to map device memory directly into user space using mmap
  • Getting direct access to user buffers

Block Device Drivers

  • Anatomy of a block device: example RAM disk driver

USB Device Drivers

  • How USB devices work with the kernel and an introduction to Linux USB device model.

Network Device Drivers

  • Anatomy of a network device: example loop-back interface

Board Support Packages

  • Customising the Linux configuration menus