http://ocw.cs.pub.ro/courses/ 2026-06-08T07:49:24+03:00 http://ocw.cs.pub.ro/courses/ http://ocw.cs.pub.ro/courses/lib/tpl/arctic/images/favicon.ico text/html 2025-08-03T10:12:37+03:00 http://ocw.cs.pub.ro/courses/ass/labs-2024/04/tasks/01?rev=1754205157&do=diff 01. Preparation The Linux kernel is comprised of numerous modules. These can be in-tree (part of the kernel source structure) or out-of-tree (independent modules). While there are some limitations when writing out-of-tree modules, such as restricted access to certain functions, this generally doesn't affect your ability to write drivers. text/html 2025-08-03T10:12:43+03:00 http://ocw.cs.pub.ro/courses/ass/labs-2024/04/tasks/02?rev=1754205163&do=diff 02. Your first kernel module Way back when, kernels used to be monolithic, meaning that adding new functionality required recompiling and installing it, followed by a reboot. Today, things are much easier. By using the kmod daemon (man 8 kmod), users are allowed to load and unload modules (i.e.: kernel object files) on demand, without all the fuss. These modules are C programs that must implement initialization and removal functions that are called automatically. Usually, these functions regist… text/html 2025-08-03T10:12:52+03:00 http://ocw.cs.pub.ro/courses/ass/labs-2024/04/tasks/03?rev=1754205172&do=diff 03. Making a simple character device Check Google for some inspiration on Linux kernel sample character device modules. Simply take the code, try to build it / fix it (if required, since newer kernel versions may break old APIs). Also make sure to put some printk() calls for debugging (if they're not already in the sample code). text/html 2025-08-03T10:12:58+03:00 http://ocw.cs.pub.ro/courses/ass/labs-2024/04/tasks/04?rev=1754205178&do=diff 04. Writing to a serial device (UART) Download & read the i.MX8M's Reference Manual, chapter 16.2. Ahem, not really all of it, just check the memory map / register definition for UTXD and UTS. Next, we will enhance our character device to print the using IMX UART peripheral using a simple MMIO interface. Useful resources for mapping, reading & writing IO memory: <https://www.kernel.org/doc/html/latest/driver-api/device-io.html> (read the introduction + MMIO parts).