March 25, 2019

Linux Device Drivers Demystified


  • September 23, 1999
  • By James Andrews

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. Below we try to demystify Linux device drivers, with the aim of smoothing device selection during installs.

Everything is a file

Skip this section if you aren't interested in the inside technical details.

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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