Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By : Kaiwan N Billimoria
Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By: Kaiwan N Billimoria

Overview of this book

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization is an ideal companion guide to the Linux Kernel Programming book. This book provides a comprehensive introduction for those new to Linux device driver development and will have you up and running with writing misc class character device driver code (on the 5.4 LTS Linux kernel) in next to no time. You'll begin by learning how to write a simple and complete misc class character driver before interfacing your driver with user-mode processes via procfs, sysfs, debugfs, netlink sockets, and ioctl. You'll then find out how to work with hardware I/O memory. The book covers working with hardware interrupts in depth and helps you understand interrupt request (IRQ) allocation, threaded IRQ handlers, tasklets, and softirqs. You'll also explore the practical usage of useful kernel mechanisms, setting up delays, timers, kernel threads, and workqueues. Finally, you'll discover how to deal with the complexity of kernel synchronization with locking technologies (mutexes, spinlocks, and atomic/refcount operators), including more advanced topics such as cache effects, a primer on lock-free techniques, deadlock avoidance (with lockdep), and kernel lock debugging techniques. By the end of this Linux kernel book, you'll have learned the fundamentals of writing Linux character device driver code for real-world projects and products.
Table of Contents (11 chapters)
Section 1: Character Device Driver Basics
User-Kernel Communication Pathways
Handling Hardware Interrupts
Working with Kernel Timers, Threads, and Workqueues
Section 2: Delving Deeper

Port I/O a few remaining points to note

A few more or less miscellaneous points remain on PIO that you as a driver author should take note of:

  • Just like MMIO provides the repeating I/O routines (recall the ioread|iowrite[8|16|32|64]_rep() helpers), PMIO (or PIO) provides somewhat similar repeating functionality for those cases where you'd like to read or write the same I/O port multiple times. These are the so-called string versions of the regular port helper routines; they have an s in their name to remind you of this. The kernel source contains a comment that neatly sums this up:
// include/asm-generic/io.h
* {in,out}s{b,w,l}{,_p}() are variants of the above that repeatedly access a
* single I/O port multiple times.
we don't show the complete code below, just the 'signature' as such
void insb(unsigned long addr, void *buffer, unsigned int count);
void insw(unsigned long addr, void *buffer, unsigned int count);
void insl(unsigned long addr,...