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

Writing codec class drivers

In order to be coupled together, machine, platform, and codec entities need dedicated drivers. The codec class driver is the most basic. It implements code that should leverage the codec device and expose its hardware properties so that user space tools such as amixer can play with it. The codec class driver is and should be platform-independent. The same codec driver can be used whatever the platform. Since it targets a specific codec, it should contain audio controls, audio interface capabilities, a codec DAPM definition, and I/O functions. Each codec driver must fulfill the following specifications:

  • Provide an interface to other modules by defining DAI and PCM configurations.
  • Provide codec control IO hooks (using I2C or SPI or both APIs).
  • Expose additional kcontrols (kernel controls) as needed for userspace utilities to dynamically control module behavior.
  • Optionally, define DAPM widgets and establish DAPM routes for dynamic power...