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

Code view 1  the IXGB network driver

It's time to look at some code. Let's take a look at some small portions of code for the Intel IXGB network adapter driver (which drives several Intel network adapters in the 82597EX series). Among the many available on the market, Intel has a product line called the IXGB network adapter. The controller is the Intel 82597EX; these are typically 10-gigabit ethernet adapters meant for servers (Intel's product brief on this controller can be found at 

Figure 4.1 – The Intel PRO/10GbE LR server adapter (IXGB, 82597EX) network adapter

First, let's take a look at it invoking request_irq() to allocate the IRQ line:

// drivers/net/ethernet/intel/ixgb/ixgb_main.c
ixgb_up(struct ixgb_adapter *adapter)
struct net_device *netdev = adapter->netdev;
int err, irq_flags = IRQF_SHARED;