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Mastering Embedded Linux Development

Mastering Embedded Linux Development

By : Frank Vasquez, Mr. Chris Simmonds
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Mastering Embedded Linux Development

Mastering Embedded Linux Development

By: Frank Vasquez, Mr. Chris Simmonds

Overview of this book

Mastering Embedded Linux Development' is designed to be both a learning resource and a reference for your embedded Linux projects. The book starts by breaking down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. First, you will download and install a pre-built toolchain. After that, you will cross-compile each of the remaining three elements from scratch and learn to automate the process using Buildroot and the Yocto Project. The book progresses with coverage of over-the-air software updates and rapid prototyping with add-on boards. Two new chapters tackle modern development practices including Python packaging and deploying containerized applications. These are followed by a chapter on writing multithreaded code and another on techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in user space or in the Linux kernel itself. In addition to GDB, the book also covers the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this book, you will be able to create efficient and secure embedded devices with Linux that will delight your users.
Table of Contents (28 chapters)
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1
Part 1: Elements of Embedded Linux
7
Part 2: Building Embedded Linux Images
11
Part 3: System Architecture and Design Decisions
18
Part 4: Developing Applications
23
Part 5: Debugging and Optimizing Performance

Powering down peripherals

The discussion up to now has been about CPUs and how to reduce power consumption when they are running or idling. Now it is time to focus on other parts of the system and see whether we can achieve power savings here.

In the Linux kernel, this is managed by the runtime power management system, or runtime pm for short. It works with drivers that support runtime pm by shutting down those that are not in use and waking them again when they are next needed.

It is dynamic and should be transparent to user space. It is up to the device driver to decide how to power down the hardware. Typically, runtime pm includes turning off the clock to the subsystem, also known as clock gating, and turning off core circuitry where possible.

Runtime power management is exposed via a sysfs interface. Each device has a subdirectory named power where you will find these files:

  • control: This allows user space to determine whether runtime pm is used on this...

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