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Linux Device Drivers Development

Linux Device Drivers Development

By : John Madieu
4 (30)
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Linux Device Drivers Development

Linux Device Drivers Development

4 (30)
By: John Madieu

Overview of this book

Linux kernel is a complex, portable, modular and widely used piece of software, running on around 80% of servers and embedded systems in more than half of devices throughout the World. Device drivers play a critical role in how well a Linux system performs. As Linux has turned out to be one of the most popular operating systems used, the interest in developing proprietary device drivers is also increasing steadily. This book will initially help you understand the basics of drivers as well as prepare for the long journey through the Linux Kernel. This book then covers drivers development based on various Linux subsystems such as memory management, PWM, RTC, IIO, IRQ management, and so on. The book also offers a practical approach on direct memory access and network device drivers. By the end of this book, you will be comfortable with the concept of device driver development and will be in a position to write any device driver from scratch using the latest kernel version (v4.13 at the time of writing this book).
Table of Contents (23 chapters)
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1
Introduction to Kernel Development

PWM consumer interface

A consumer is the device that actually uses PWM channels. A PWM channel is represented in the kernel as an instance of the struct pwm_device structure:

struct pwm_device { 
   const char *label; 
   unsigned long flags; 
   unsigned int hwpwm; 
   unsigned int pwm; 
   struct pwm_chip *chip; 
   void *chip_data; 
 
  unsigned int period;     /* in nanoseconds */ 
  unsigned int duty_cycle; /* in nanoseconds */ 
  enum pwm_polarity polarity; 
}; 
  • Label: This is the name of this PWM device
  • Flags: This represents the flags associated with the PWM device
  • hwpw: This is a relative index of the PWM device, local to the chip
  • pwm: This is a system global index of the PWM device
  • chip: This is a PWM chip, the controller providing this PWM device
  • chip_data: This is chip-private data associated with this PWM device

Since kernel v4.7, the structure changed to:

...

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