Book Image

Mastering Embedded Linux Programming - Second Edition

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming - Second Edition

By: Chris Simmonds

Overview of this book

Embedded Linux runs many of the devices we use every day, from smart TVs to WiFi routers, test equipment to industrial controllers - all of them have Linux at their heart. Linux is a core technology in the implementation of the inter-connected world of the Internet of Things. The comprehensive guide shows you the technologies and techniques required to build Linux into embedded systems. You will begin by learning about the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. You’ll see how to create each of these elements from scratch, and how to automate the process using Buildroot and the Yocto Project. Moving on, you’ll find out how to implement an effective storage strategy for flash memory chips, and how to install updates to the device remotely once it is deployed. You’ll also get to know the key aspects of writing code for embedded Linux, such as how to access hardware from applications, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters show you how to debug your code, both in applications and in the Linux kernel, and how to profile the system so that you can look out for performance bottlenecks. By the end of the book, you will have a complete overview of the steps required to create a successful embedded Linux system.
Table of Contents (17 chapters)

Character devices

Character devices are identified in user space by a special file called a device node. This file name is mapped to a device driver using the major and minor numbers associated with it. Broadly speaking, the major number maps the device node to a particular device driver, and the minor number tells the driver which interface is being accessed. For example, the device node of the first serial port on the ARM Versatile PB is named /dev/ttyAMA0, and it has major number 204 and minor number 64. The device node for the second serial port has the same major number, since it is handled by the same device driver, but the minor number is 65. We can see the numbers for all four serial ports from the directory listing here:

# ls -l /dev/ttyAMA*
crw-rw---- 1 root root 204, 64 Jan 1 1970 /dev/ttyAMA0
crw-rw---- 1 root root 204, 65 Jan 1 1970 /dev...