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

64-bit atomic integer operators

As mentioned at the start of this topic, the set of atomic_t integer operators we have dealt with so far all operate on traditional 32-bit integers (this discussion doesn't apply to the newer refcount_t interfaces; they anyway operate upon both 32 and 64-bit quantities). Obviously, with 64-bit systems becoming the norm rather than the exception nowadays, the kernel community provides an identical set of atomic integer operators for 64-bit integers. The difference is as follows:

  • Declare the 64-bit atomic integer as a variable of type atomic64_t (that is, atomic_long_t).
  • For all operators, in place of the atomic_ prefix, use the atomic64_ prefix. 

So, take the following examples:

  • In place of ATOMIC_INIT(), use ATOMIC64_INIT().
  • In place of atomic_read(), use atomic64_read().
  • In place of atomic64_dec_if_positive(), use atomic64_dec_if_positive().
Recent C and C++ language standards – C11 and C++11 –...