Linux Device Driver

Device controllers are typically connected to the CPU through their respectively named buses (collection of physical lines) — for example, the PCI bus, the IDE bus, etc. In today’s embedded world, we encounter more micro-controllers than CPUs; these are the CPU plus various device controllers built onto a single chip. This effective embedding of device controllers primarily reduces cost and space, making it suitable for embedded systems. In such cases, the buses are integrated into the chip itself.





In short, a device driver has two parts, which are: a) device-specific, and b) OS-specific.
 The device-specific portion of a device driver remains the same across all operating systems, and is more about understanding and decoding the device data sheets than software programming.
the OS-specific portion is the one that is tightly coupled with the OS mechanisms of user interfaces, and thus differentiates a Linux device driver from a Windows device driver and from a MacOS device driver.


Linux systems have a way of identifying device files via major device numbers, which identify modules serving device files or a group of devices, and minor device numbers, which identify a specific device among a group of devices that a major device number specifies. In the driver code, we can define these numbers as constants or they can be allocated dynamically.