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Linux Device Drivers Development

You're reading from   Linux Device Drivers Development Develop customized drivers for embedded Linux

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Product type Paperback
Published in Oct 2017
Publisher Packt
ISBN-13 9781785280009
Length 586 pages
Edition 1st Edition
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Author (1):
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John Madieu John Madieu
Author Profile Icon John Madieu
John Madieu
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Table of Contents (23) Chapters Close

Preface 1. Introduction to Kernel Development FREE CHAPTER 2. Device Driver Basis 3. Kernel Facilities and Helper Functions 4. Character Device Drivers 5. Platform Device Drivers 6. The Concept of Device Tree 7. I2C Client Drivers 8. SPI Device Drivers 9. Regmap API – A Register Map Abstraction 10. IIO Framework 11. Kernel Memory Management 12. DMA – Direct Memory Access 13. The Linux Device Model 14. Pin Control and GPIO Subsystem 15. GPIO Controller Drivers – gpio_chip 16. Advanced IRQ Management 17. Input Devices Drivers 18. RTC Drivers 19. PWM Drivers 20. Regulator Framework 21. Framebuffer Drivers 22. Network Interface Card Drivers

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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