Book Image

Mastering Linux Device Driver Development

By : John Madieu
Book Image

Mastering Linux Device Driver Development

By: John Madieu

Overview of this book

Linux is one of the fastest-growing operating systems around the world, and in the last few years, the Linux kernel has evolved significantly to support a wide variety of embedded devices with its improved subsystems and a range of new features. With this book, you’ll find out how you can enhance your skills to write custom device drivers for your Linux operating system. Mastering Linux Device Driver Development provides complete coverage of kernel topics, including video and audio frameworks, that usually go unaddressed. You’ll work with some of the most complex and impactful Linux kernel frameworks, such as PCI, ALSA for SoC, and Video4Linux2, and discover expert tips and best practices along the way. In addition to this, you’ll understand how to make the most of frameworks such as NVMEM and Watchdog. Once you’ve got to grips with Linux kernel helpers, you’ll advance to working with special device types such as Multi-Function Devices (MFD) followed by video and audio device drivers. By the end of this book, you’ll be able to write feature-rich device drivers and integrate them with some of the most complex Linux kernel frameworks, including V4L2 and ALSA for SoC.
Table of Contents (19 chapters)
1
Section 1:Kernel Core Frameworks for Embedded Device Driver Development
6
Section 2: Multimedia and Power Saving in Embedded Linux Systems
13
Section 3: Staying Up to Date with Other Linux Kernel Subsystems

Introduction to ASoC

From an architectural point of view, the ASoC subsystem elements and their relationship can be represented as follows:

Figure 5.1 – ASoC architecture

The preceding diagram summarizes the new ASoC architecture, in which the machine entity wraps both platform and codec entities.

In the ASoC implementation prior to kernel v4.18, there was strict separation between SoC audio codec devices (represented by struct snd_soc_codec these days) and SoC platform interfaces (represented by struct snd_soc_platform) and their respective digital audio interfaces. However, there was an increasing amount of similar code between codecs, platforms, and other components. This led to a new and generic approach, the concept of the component. All drivers have been moved over to this new generic component, platform code has been removed, and everything has been refactored so that nowadays, we only talk about struct snd_soc_component (which may refer to...