Example char device driver linux

 · Device drivers have an associated major and minor number. For example, /dev/ram0 and /dev/null are associated with a driver with major number 1, and /dev/tty0 and /dev/ttyS0 are associated with a driver with major number 4. The major number is used by the kernel to identify the correct device driver when the device is accessed. For example, every character driver needs to define a function that reads from the device. The file_operations structure holds the address of the module's function that performs that operation. Here is what the definition looks like for kernel struct file_operations { struct module *owner; loff_t (*llseek) (struct file *, loff_t, int); ssize_t (*read) (struct file *, char __user *, size_t, loff_t .  · Example of character device is: /dev/consoles or /dev/ttyS0. These devices are accessed as a stream of bytes. Example of block device: /dev/sdxn. Block devices allow the programmer to read and write any size of the block. Pseudo devices act as device drivers without an actual device. Examples of pseudo devices are /dev/null, /dev/zero, /dev/pf etc.

Device drivers have an associated major and minor number. For example, /dev/ram0 and /dev/null are associated with a driver with major number 1, and /dev/tty0 and /dev/ttyS0 are associated with a driver with major number 4. The major number is used by the kernel to identify the correct device driver when the device is accessed. In this post, we would be writing a Linux device driver for a hypothetical character device which reverses any string that is given to it. i.e. If we write any string to the device file represented by the device and then read that file, we get the string written earlier but reversed (for eg., myDev being our device, echo “hello” /dev/myDev ; cat /dev/ myDev would print “olleh”). This article, which is part of the series on Linux device drivers, deals with the various concepts related to character drivers and their implementation. Shweta, at her PC in her hostel room, was all set to explore the characters of Linux character drivers, before it was taught in class.

20 окт. г. Implements UART char device driver for example. Uses following Linux facilities: module, platform driver, file operations (read/write, mmap. 14 мар. г. A character device is one of the simplest ways to communicate with a module in the Linux kernel. These devices are presented as special. 16 авг. г. In our character driver we are keeping name of our device is “mydev”. #include Below is the example of make file.