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)
Section 1:Kernel Core Frameworks for Embedded Device Driver Development
Section 2: Multimedia and Power Saving in Embedded Linux Systems
Section 3: Staying Up to Date with Other Linux Kernel Subsystems

Chapter 9:Leveraging the V4L2 API from the User Space

The main purpose of device drivers is controlling and leveraging the underlying hardware while exposing functionalities to users. These users may be applications running in user space or other kernel drivers. While the two previous chapters dealt with V4L2 device drivers, in this chapter, we will learn how to take advantage of V4L2 device functionalities exposed by the kernel. We will start by describing and enumerating user space V4L2 APIs, and then we will learn how to leverage those APIs to grab video data from the sensor, including mangling the sensor properties.

This chapter will cover the following topics:

  • V4L2 user space APIs
  • Video device property management from user space
  • Buffer management from user space
  • V4L2 user space tools