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

You're reading from  Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

Product type Book
Published in Mar 2021
Publisher Packt
ISBN-13 9781801079518
Pages 452 pages
Edition 1st Edition
Languages
Author (1):
Kaiwan N. Billimoria Kaiwan N. Billimoria
Profile icon Kaiwan N. Billimoria
Toc

Table of Contents (11) Chapters close

Preface 1. Section 1: Character Device Driver Basics
2. Writing a Simple misc Character Device Driver 3. User-Kernel Communication Pathways 4. Working with Hardware I/O Memory 5. Handling Hardware Interrupts 6. Working with Kernel Timers, Threads, and Workqueues 7. Section 2: Delving Deeper
8. Kernel Synchronization - Part 1 9. Kernel Synchronization - Part 2 10. Other Books You May Enjoy

Questions

  1. Spot the bug(s) in the following pseudocode:
static my_chip_tasklet(void)
{
// ... process data
if (!copy_to_user(to, from, count)) {
pr_warn("..."); [...]
}
}
static irqreturn_t chip_hardisr(int irq, void *data)
{
// ack irq
// << ... fetch data into kfifo ... >>
// << ... call func_a(), delay, then call func_b() >>
func_a();
usleep(100); // 100 us delay required here! see datasheet pg ...
func_b();
tasklet_schedule(...);
return IRQ_HANDLED;
}
my_chip_probe(...)
{
// ...
request_irq(CHIP_IRQ, chip_hardisr, ...);
// ...
tasklet_init(...);
}
  1. timer_simple_check: Enhance the timer_simple kernel module so that it checks the amount of time that elapsed between setting up a timeout and it actually being serviced.
  2. kclock: Write a kernel module that sets up a kernel timer so that it times out every second. Then, use this to print the timestamp to the kernel log to get, in effect, a simple "clock app...
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