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

Adding power management capabilities to device drivers

Device drivers on their own can implement a distinct power management capability, which is known as runtime power management. Not all devices support runtime power management. However, those that do must export some callbacks for controlling their power state depending on the user or system’s policy decisions. As we have seen earlier, this is device-specific. In this section, we will learn how to extend device driver capabilities with power management support.

Though device drivers provide runtime power management callbacks, they also facilitate and participate in the system sleep state by providing another set of callbacks, where each set participates in a particular system sleep state. Whenever the system needs to enter or resume from a given set, the kernel will walk through each driver that provided callbacks for this state and then invoke them in a precise order. Simply speaking, device power management consists...