#Make .o file driver kernel linux how to#

But inside this driver, each of these ports is also identified by the unique number, and this is a device Minor number. Both of these ports are handled by the same driver, and they share one Major number. For example, a serial port adapter may contain two hardware ports. Every device driver can support multiple “sub-devices”.

This number assigning by the kernel during device registration. Inside the Linux kernel, every device is identified not by a symbolic name but by a unique number – the device’s major number.

This is a Major and Minor number of this device. Symbol C, in the beginning, means that this device is a character device.Īlso, you can find here two strange numbers: 4 and 64.

#Make .o file driver kernel linux how to#

Here I am describing how to write a simple Linux kernel module which can create one or multiple character device.ĭetection of the device type in /dev directory is pretty simple. Userspace programs can easily open, read, write, and custom control requests with such device files. Actually, most of the pseudo-devices in /dev are character devices: serial ports, modems, sound, and video adapters, keyboards, some custom I/O interfaces. These devices are presented as special files in a /dev directory and support direct reading and writing of any data, byte by byte, like a stream. A character device is one of the simplest ways to communicate with a module in the Linux kernel.