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
Credits
Foreword
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Block devices


Block devices are also associated with a device node, which also has major and minor numbers.

Note

Although character and block devices are identified using major and minor numbers, they are in different namespaces. A character driver with a major number 4 is in no way related to a block driver with a major number 4.

With block devices, the major number is used to identify the device driver and the minor number is used to identify the partition. Let's look at the MMC driver as an example:

# ls -l /dev/mmcblk*

brw-------    1 root root  179,   0 Jan  1  1970 /dev/mmcblk0
brw-------    1 root root  179,   1 Jan  1  1970 /dev/mmcblk0p1
brw-------    1 root root  179,   2 Jan  1  1970 /dev/mmcblk0p2
brw-------    1 root root  179,   8 Jan  1  1970 /dev/mmcblk1
brw-------    1 root root  179,   9 Jan  1  1970 /dev/mmcblk1p1
brw-------    1 root root  179,  10 Jan  1  1970 /dev/mmcblk1p2

The major number is 179 (look it up in devices.txt!). The minor numbers are used in ranges to identify...