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ac6 >> ac6-training >> Operating Systems >> Linux >> Linux Drivers

D3 Linux Drivers

Writing Linux Drivers

Objectives

Mastering kernel development and debug tools
Discovering multi-core programming in the Linux kernel
Programming IOs, interrupts, timers and DMA
Installing and integrating drivers inside Linux kernel
Managing synchronous and asynchronous IOs and ioctl
Writing a complete character driver
Understanding specificities of 2.6 and 3.x versions
Mastering kernel debugging technics with Lauterbach JTAG probes.

	Labs are conducted on target boards, that can be:
	Dual Cortex/A7-based "STM32MP15-DISCO" boards from STMicroelectronics.
	Quad Cortex/A9-based "SabreLite" boards from NXP.
	Quad Cortex/A53-based "imx8q-evk" boards from NXP.
	We use a recent (4.x) linux kernel, as supported by the chip supplier.

Target audience

This course is for engineers that install Linux on a custom platform and have to create specific device drivers.

Course environment

Printed course material (in English)
One Linux PC for two trainees.
One target platform for two trainees

Prerequisite

Good C programming skills
Preferably knowledge of Linux user programming (see our D0 - Linux user mode programming course or oD0 - Linux User Mode Programming course)

FIRST DAY

Linux kernel programming

Development in the Linux kernel
Memory allocation
Linked lists

Exercise:	Writing the "hello world" kernel module
Exercise:	Adding a driver to kernel sources and configuration menu
Exercise:	Using module parameters
Exercise:	Writing interdependent modules using memory allocations, reference counting and linked lists

Linux kernel debugging

The /proc and debugfs filesystems
Traces
The kernel Dynamic Debugging interface
The Kernel Address Sanitizer
Debugging memory problems with kmemleak
Using the Undefined Behavior Sanitizer
Code coverage using gcov
Debugging with kgdb
Debugging with a JTAG probe

Exercise:	Display dynamic traces on the running kernel
Exercise:	Debug a module initialization using kgdb

Kernel multi-tasking

Task handling
Concurrent programming
Timers
Kernel threads

Exercise:

Fixing race conditions in the previous lab with mutexes

SECOND DAY

Introduction to Linux drivers

Accessing the device driver from user space
Driver registration

Exercise:	Step by step implementation of a character driver:
	•	driver registration (major/minor reservation) and device special file creation (/dev)

Driver I/O functions

Kernel structures used by drivers
Opening and closing devices
Data transfers
Controlling the device
Mapping device memory

Exercise:	Step by step implementation of a character driver:
	•	Implementing open and release
	•	Implementing read and write
	•	Implementing ioctl
	•	Implementing mmap

THIRD DAY

Synchronous and asynchronous requests

Task synchronization
Synchronous request
Asynchronous requests

Exercise:	implementation of a pipe-like driver:
	•	implementing waiting and waking
	•	adding non-blocking, asynchronous and multiplexed operations (O_NONBLOCK, SIGIO, poll/select)

Input/Output and interrupts

Memory-mapped registers
Interrupts
Gpios
User-level access through /sys or the GPIO character driver

Exercise:	Polling gpio driver with raw register access
Exercise:	Interrupt-based gpio driver with raw register access
Exercise:	gpio driver using the gpiolib

Busses

Plug-and-Play management
Static devices declaration

in the BSP code
in the device tree

Platform bus
PCI
SPI
Power management

System sleep
Implementing power management in drivers
Remote wakeup

Exercise:	Implementing a platform driver and customizing the device tree to associate it to its device (a serial port)
Exercise:	Implementing power management in the previous driver
Exercise:	Implementing remote wakeup in the previous driver

FOURTH DAY

Linux Driver Model

Linux Driver Model Architecture

Overview
Classes
Busses

Hot plug management

Plugging devices
Removing devices

Writing udev rules

Exercise:	Writing a custom class driver
Exercise:	Writing a misc driver

DMA

Direct Memory Access

DMA scenarios
Buffer access

DMA programming

Bus master DMA
Slave DMA

Memory barriers

Exercise:

Implementing slave DMA in a serial port driver

ANNEXES

USB Drivers

The USB bus
USB devices
User-space USB interface
USB descriptors
USB requests
USB device drivers

Exercise:

Writing a USB host driver

Network drivers

structures

network interface representation (struct net_device)
network packet (struct sk_buff)

scatter/gather
interface

receiving packets
sending packets
lost packets management
network interface statistics

New network API (NAPI)

"interrupt mitigation" (suppression of unneeded IRQs)
"packet throttling" (suppression of packets in the driver itself when system is overwhelmed)

Memory management

Virtual Memory
Memory Allocation

Free page management
Normal memory allocation
Virtual memory allocation
Huge allocations

Duration	Cost	Calendar
4 days	2610 € HT
Last update: 15 November 2022
This course, designed for face-to-face delivery, can be provided either in our Paris training center or, worldwide, on your premises. Scheduled classes are confirmed as soon as there is a confirmed booking.
A version tailored for live online delivery is available under reference oD3 - Linux Drivers (online Training)
To book a training session or for more information, please contact us on info@ac6-training.com. Registrations are accepted till one week before the start date for scheduled classes. For late registrations, please consult us. You can also fill and send us the registration form
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