port of the ldd3 source code examples to linux 3.x
ldd3 is Linux Device Drivers, Third Edition. This is a great book about how to write linux device drivers. You can get this book and its source code examples free from http://lwn.net/Kernel/LDD3/.
But, the souce code examples in the book are based on linux 2.6.10, which was released in 2005. This means that all the original examples won't compile in the current linux 3.x branch. I've ported all examples to the longterm stable branch after linux 3.0, including:
| branch | original release date |
|---|---|
| linux 3.0 | July 2011 |
| linux 3.2 | January 2012 |
| linux 3.4 | May 2012 |
| linux 3.10 | June 2013 |
| linux 3.12 | November 2013 |
| linux 3.14 | March 2014 |
| linux 3.18 | December 2014 |
The key difference between this project and other porting attemps is that all these examples not only compile on the modern kernel version, but they also RUN on the modern kernel!
a. clone this repo
b. checkout to branch which is nearest to your linux kernel version
c. just type make to build ldd3 examples
(This section is for developers who want to port ldd3 examples by themselves, reading previous quick start section is enough for the beginners.)
a. clone linux-stable repo from http://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
b. Use git log to find out who changed what when. Then determine what is causing it to not compile. then change ldd3 examples according to those commits.
If compiling errors are 'XXX symbol not found', find root causing commits by:
$git log -p <XXX symbol's file path in original linux version> |\
grep <XXX symbol>
c. Use git bisect when git log fails to work.
First you should understand the original examples,
Second you should understand the related commits in the modern linux version.
If you still can't fix the bug, debug it using below methods:
a. compare similar driver code in linux-stable. For example: debuging snull by refering to loopback.c, debug sbull by refering to loop.c...
b. printk
c. gdb/qemu. compile busybox+linux running in qemu, load buggy module, use gdb to debug it. Embedded Linux From Scratch is useful when doing such tasks, refer to http://free-electrons.com/docs/elfs/.