Question

I’m currently doing a course about Operating Systems.

I understand that a kernel is a core part of an operating system that acts as a bridge between user applications and the data processing elements of a computer such as the CPU.

Why do we need Drivers then (e.g Touchpad drivers), doesn’t the kernel control all computer hardware?

Answer 1

Because there are literally thousands (if not hundreds of thousands) of companies that produce hardware devices. The Operating System company cannot write software to handle all of them, so they provide a generic programming model using which those hardware companies can write software that could talk to their hardware.

Important to note is that although drivers are not actually part of the kernel as such, they do have some low-level privileges (direct access to hardware) because their code runs in Executive mode, unlike normal applications which run in User mode and generally do not access hardware directly. The whole point is that once the OS provides a way to write hardware-controlling software (called drivers), any vendor or person is free to write a software that could take advantage of the specialized features of their/his hardware device.

Also note that some hardware devices follow well-known standard (such as keyboards, mice, many video drivers, monitors etc.) and most OS come with built-in support for those devices. On the other hand, some devices do not have or follow standards, while still other can have both kinds of features, i.e. a subset of features that could be accessed by the default driver, plus a subset of features that doesn’t follow any standards and thus is not supported by default driver. In all such cases, hardware manufacturers supply their own driver that knows the ins and outs of their hardware and therefore can take advantage of all features efficiently.