EmbLogic » Device Drivers https://www.emblogic.com/blog Embedded System and ARM Training Tue, 03 Mar 2020 13:00:06 +0000 en-US hourly 1 http://wordpress.org/?v=3.9.1 Project 05: Character Device Driver https://www.emblogic.com/blog/11/project-05-character-device-driver/ https://www.emblogic.com/blog/11/project-05-character-device-driver/#comments Fri, 02 Nov 2012 16:52:39 +0000 http://emblogic.org/blog/?p=5628 Continue reading →]]> Modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system. Without modules, we would have to build monolithic kernels and add new functionality directly into the kernel image. Besides having larger kernels, this has the disadvantage of requiring us to rebuild and reboot the kernel every time we want new functionality.

]]> https://www.emblogic.com/blog/11/project-05-character-device-driver/feed/ 14 What is Device Drivers https://www.emblogic.com/blog/01/what-is-device-drivers/ https://www.emblogic.com/blog/01/what-is-device-drivers/#comments Wed, 11 Jan 2012 19:34:04 +0000 http://emblogic.org/blog/?p=1621 Continue reading →]]> People new to Linux often hear that it has excellent support for all kinds of cards and that the device drivers are stable and fast. Sometimes, though, setting up devices under Linux is often not all plug-and-play.

Everything is a file

Many modern operating systems have a method for installing special files to make hardware work. On the Apple Mac, for instance, the drivers for the hardware devices are usually special files that go in the System Extensions folder. Linux also has special files that it uses to control the hardware.

Linux device drivers work through special kernel code that directly accesses the hardware. To make the services that the card or other device offers available to normal user programs, the kernel uses the special files in /dev

One end of the file in /dev can be opened normally and the other end is attached to the kernel. That is of course an oversimplification, but I think you get the general idea: hardware, kernel, special file, user program and the same path back from user program to hardware. There are two forms of the kernel portion of this equation: compiled-in drivers that are coded in permanently when the kernel is built, and modules.

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