Book Image

Mastering Embedded Linux Programming

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming

By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (22 chapters)
Mastering Embedded Linux Programming
About the Author
About the Reviewers

Loading kernel modules

You can load, unload and list modules using the simple insmod, lsmod, and rmmod commands. Here they are shown loading the dummy driver:

# insmod /lib/modules/4.1.10/kernel/drivers/dummy.ko
# lsmod
dummy 1248 0 - Live 0xbf009000 (O)
# rmmod dummy

If the module is placed in a subdirectory in /lib/modules/<kernel release>, as in the example, you can create a modules dependency database using the command depmod:

# depmod -a
# ls /lib/modules/4.1.10/
kernel               modules.builtin.bin  modules.order
modules.alias        modules.dep          modules.softdep
modules.alias.bin    modules.dep.bin      modules.symbols
modules.builtin      modules.devname      modules.symbols.bin

The information in the module.* files is used by the command modprobe to locate a module by name rather than the full path. modprobe has many other features which are described in the manual.

The module dependency information is also used by device managers, udev in particular. When new hardware...