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

Chapter 3: Delving into the MFD Subsystem and Syscon API

The increasingly dense integration of devices has led to a kind of device that is made up of several other devices or IPs that can achieve a dedicated function. With the advent of this device, a new subsystem appeared in the Linux kernel. These are MFDs, which stands for multi-function devices. These devices are physically seen as standalone devices, but from a software point of view, these are represented in a parent-child relationship, where the children are subdevices.

While some I2C- and SPI-based devices/subdevices might need either some hacks or configurations prior to being added to the system, there are also MMIO-based devices/subdevices where zero conf/hacks are required as they just need to share the main device's register region between subdevices. The simple-mfd helper has then been introduced to handle zero conf/hacks subdevice registering, and syscon has been introduced for sharing a device's memory...