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

Writing the platform class driver

The platform driver registers the PCM driver, CPU DAI driver, and their operation functions, pre-allocates buffers for PCM components, and sets playback and capture operations as applicable. In other words, the platform driver contains the audio DMA engine and audio interface drivers (for example, I2S, AC97, and PCM) for that platform.

The platform driver targets the SoC the platform is made of. It concerns the platform's DMA, which is how audio data transits between each block in the SoC, and CPU DAI, which is the path the CPU uses to send/carry audio data to/from the codec. Such a driver has two important data structures: struct snd_soc_component_driver and struct snd_soc_dai_driver. The former is responsible for DMA data management, and the latter is responsible for the parameter configuration of the DAI. However, both of these data structures have already been described while dealing with codec class drivers. Thus, this part will just deal...