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

Introducing NVMEM data structures and APIs

NVMEM is a small framework with a reduced set of APIs and data structures. In this section, we will introduce those APIs and data structures, as well as the concept of a cell, which is the base of this framework.

NVMEM is based on the producer/consumer pattern, just like the clock framework described in Chapter 4, Storming the Common Clock Framework. There is a single driver for the NVMEM device, exposing the device cells so that they can be accessed and manipulated by consumer drivers. While the NVMEM device driver must include <linux/nvmem-provider.h>, consumers have to include <linux/nvmem-consumer.h>. This framework has only a few data structures, among which is struct nvmem_device, which looks as follows:

struct nvmem_device {
    const char  *name;
    struct module *owner;
    struct device dev;
    int stride;
   ...