Summary

Device drivers have the job of handling devices, usually physical hardware but sometimes virtual interfaces, and presenting them to the user space in a consistent and useful way. Linux device drivers fall into three broad categories: character, block, and network. Of the three, the character driver interface is the most flexible and therefore, the most common. Linux drivers fit into a framework known as the driver model, which is exposed through sysfs. Pretty much the entire state of the devices and drivers is visible in /sys.

Each embedded system has its own unique set of hardware interfaces and requirements. Linux provides drivers for most standard interfaces, and by selecting the right kernel configuration, you can get a working target board very quickly. This leaves you with the non-standard components, for which you will have to add your own device support.

In some cases, you can sidestep the issue by using generic drivers for GPIO, I2C, and so on, and write user...