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

Chapter 5: ALSA SoC Framework – Leveraging Codec and Platform Class Drivers

Audio is an analog phenomenon that can be produced in all sorts of ways. Voice and audio have been communication media since the beginning of humanity. Almost every kernel provides audio support to userspace applications as an interaction mechanism between computers and humans. To achieve this, the Linux kernel provides a set of APIs known as ALSA, which stands for Advanced Linux Sound Architecture.

ALSA was designed for desktop computers, not taking into account embedded world constraints. This added a lot of drawbacks when it came to dealing with embedded devices, such as the following:

  • Strong coupling between codec and CPU code, leading to difficulties in porting and code duplication.
  • No standard way to handle notifications about users' audio-related behavior. In mobile scenarios, users' audio-related behaviors are frequent, so a special mechanism is needed.
  • In the original...