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

V4L2 user space tools

So far, we have learned how to write user space code to interact with the driver in the kernel. For rapid prototyping and testing, we could leverage some community-provided V4L2 user space tools. By using those tools, we can focus on the system design and validate the camera system. The most well-known tool is v4l2-ctl, which we will focus on; it is shipped with the v4l-utils package.

Though it is not discussed in this chapter, there is also the yavta tool (which stands for Yet Another V4L2 Test Application), which can be used to test, debug, and control the camera subsystem.

Using v4l2-ctl

v4l2-utils is a user space application that can be used to query or configure V4L2 devices (including subdevices). This tool can help in setting up and designing fine-grained V4L2-based systems as it helps tweak and leverage the device's features.

Important note

qv4l2 is the Qt GUI equivalent of v4l2-ctl. v4l2-ctl is ideal for embedded systems, while qv4l2...