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

The concept of sub-devices

In the early days of the V4L2 subsystem, there were just two main data structures:

  • struct video_device: This is the structure through which /dev/<type>X appears.
  • struct vb2_queue: This is responsible for buffer management.

This was enough in an era when there were not that many IP blocks embedded with the video bridge. Nowadays, image blocks in SoCs embed so many IP blocks, each of which plays a specific role by offloading specific tasks, such as image resizing, image converting, and video deinterlacing functionalities. In order to use a modular approach for addressing this diversity, the concept of the sub-device has been introduced. This brings a modular approach to the software modeling of the hardware, allowing to abstract each hardware component as a software block.

With this approach, each IP block (except the bridge device) participating in the processing pipe is seen as a sub-device, even the camera sensor itself. Whereas...