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Linux Device Driver Development

Linux Device Driver Development

By : John Madieu
4.4 (7)
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Linux Device Driver Development

Linux Device Driver Development

4.4 (7)
By: John Madieu

Overview of this book

Linux is by far the most-used kernel on embedded systems. Thanks to its subsystems, the Linux kernel supports almost all of the application fields in the industrial world. This updated second edition of Linux Device Driver Development is a comprehensive introduction to the Linux kernel world and the different subsystems that it is made of, and will be useful for embedded developers from any discipline. You'll learn how to configure, tailor, and build the Linux kernel. Filled with real-world examples, the book covers each of the most-used subsystems in the embedded domains such as GPIO, direct memory access, interrupt management, and I2C/SPI device drivers. This book will show you how Linux abstracts each device from a hardware point of view and how a device is bound to its driver(s). You’ll also see how interrupts are propagated in the system as the book covers the interrupt processing mechanisms in-depth and describes every kernel structure and API involved. This new edition also addresses how not to write device drivers using user space libraries for GPIO clients, I2C, and SPI drivers. By the end of this Linux book, you’ll be able to write device drivers for most of the embedded devices out there.
Table of Contents (23 chapters)
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1
Section 1 -Linux Kernel Development Basics
6
Section 2 - Linux Kernel Platform Abstraction and Device Drivers
12
Section 3 - Making the Most out of Your Hardware
18
Section 4 - Misc Kernel Subsystems for the Embedded World

Leveraging Regmap from the user space

Register maps can be monitored from the user space via the debugfs file system. First, debugfs needs to be enabled via the CONFIG_DEBUG_FS kernel configuration option. Then, debugfs can be mounted using the following command:

mount -t debugfs none /sys/kernel/debug

After that, the debugfs register map implementation can be found under /sys/kernel/debug/regmap/. This debugfs view implemented by drivers/base/regmap/regmap-debugfs.c in kernel sources contains a register cache (mirror) for drivers/peripherals based on the Regmap API.

From the Regmap main debugfs directory, we can get the list of devices whose drivers are based on the Regmap API using the following command:

root@jetson-nano-devkit:~# ls -l /sys/kernel/debug/regmap/
drwxr-xr-x   2 root  root   0 Jan  1  1970 4-003c-power-slave
drwxr-xr-x   2 root  root   0 Jan  1...
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