Book Image

Linux Device Driver Development - Second Edition

By : John Madieu
Book Image

Linux Device Driver Development - Second Edition

By: John Madieu

Overview of this book

Linux is by far the most-used kernel on embedded systems. Thanks to its subsystems, the Linux kernel supports almost all of the application fields in the industrial world. This updated second edition of Linux Device Driver Development is a comprehensive introduction to the Linux kernel world and the different subsystems that it is made of, and will be useful for embedded developers from any discipline. You'll learn how to configure, tailor, and build the Linux kernel. Filled with real-world examples, the book covers each of the most-used subsystems in the embedded domains such as GPIO, direct memory access, interrupt management, and I2C/SPI device drivers. This book will show you how Linux abstracts each device from a hardware point of view and how a device is bound to its driver(s). You’ll also see how interrupts are propagated in the system as the book covers the interrupt processing mechanisms in-depth and describes every kernel structure and API involved. This new edition also addresses how not to write device drivers using user space libraries for GPIO clients, I2C, and SPI drivers. By the end of this Linux book, you’ll be able to write device drivers for most of the embedded devices out there.
Table of Contents (23 chapters)
1
Section 1 -Linux Kernel Development Basics
6
Section 2 - Linux Kernel Platform Abstraction and Device Drivers
12
Section 3 - Making the Most out of Your Hardware
18
Section 4 - Misc Kernel Subsystems for the Embedded World

Demystifying address translation and MMU

MMU does not only convert virtual addresses into physical ones but also protects memory from unauthorized access. Given a process, any page that needs to be accessed from this process must exist in one of its VMAs and, thus, must live in the process's page table (every process has its own).

As a recall, memory is organized by chunks of fixed-size named pages for virtual memory and frames for physical memory. The size in our case is 4 KB. However, it is defined and accessible with the PAGE_SIZE macro in the kernel. Remember, however, that page size is imposed by the hardware. Considering a 4 KB page-sized system, bytes 0 to 4095 fall on page 0, bytes 4096 to 8191 fall on page 1, and so on.

The concept of a page table is introduced to manage mapping between pages and frames. Pages are spread over tables so that each PTE corresponds to a mapping between a page and a frame. Each process is then given a set of page tables to describe all...