You're reading from Mastering Linux Device Driver Development

Product type Book

Published in Jan 2021

Publisher Packt

ISBN-13 9781789342048

Pages 646 pages

Edition 1st Edition

Languages

Concepts

Embedded Systems

Author (1):

John Madieu

Table of Contents (19) Chapters

Preface

1. Section 1:Kernel Core Frameworks for Embedded Device Driver Development

2. Chapter 1: Linux Kernel Concepts for Embedded Developers

3. Chapter 2: Leveraging the Regmap API and Simplifying the Code

4. Chapter 3: Delving into the MFD Subsystem and Syscon API

5. Chapter 4: Storming the Common Clock Framework

6. Section 2: Multimedia and Power Saving in Embedded Linux Systems

7. Chapter 5: ALSA SoC Framework – Leveraging Codec and Platform Class Drivers

8. Chapter 6: ALSA SoC Framework – Delving into the Machine Class Drivers

9. Chapter 7: Demystifying V4L2 and Video Capture Device Drivers

10. Chapter 8: Integrating with V4L2 Async and Media Controller Frameworks

11. Chapter 9:Leveraging the V4L2 API from the User Space

12. Chapter 10: Linux Kernel Power Management

13. Section 3: Staying Up to Date with Other Linux Kernel Subsystems

14. Chapter 11: Writing PCI Device Drivers

15. Chapter 12: Leveraging the NVMEM Framework

16. Chapter 13: Watchdog Device Drivers

17. Chapter 14: Linux Kernel Debugging Tips and Best Practices

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Being a source of system wakeup

The PM core allows the system to be awoken following a system suspend. A device capable of system wakeup is known as a wakeup source in PM language. For a wakeup source to operate normally, it needs a so-called wakeup event, which, most of time, is assimilated to an IRQ line. In other words, a wakeup source generates wakeup events. When a wakeup source generates a wakeup event, the wakeup source is set to the activated state through the interface provided by the wakeup event’s framework. When the event processing ends, it is set to the deactivated state. The interval between activate and deactivate indicates that the event is being processed. In this section, we will see how to make your device be a source of system wakeup in driver code.

Wakeup sources work so that when there is any wakeup event being processed in the system, suspension is not allowed. If suspension is in progress, it is terminated. The kernel abstracts wakeup sources by means...