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In Linux kernel development, spinlocks are essential synchronization primitives for protecting shared resources in interrupt contexts. This article demonstrates how to implement interrupt-safe spinlocks in a character device driver for controlling GPIO-based LEDs. We'll explore the use of spinlock functions that save and restore interrupt state ...

Introduction to SystemTap SystemTap is a powerful dynamic tracing tool that allows developers and system administrators to monitor and analyze the behavior of both the Linux kernel and user-space applications without modifying the code or restarting the process. By defining custom probes, users can track various aspects such as function calls, ...

Project Directory Structure Key project directories for STM32MP157 development: Buildroot root filesystem: /home/developer/projects/stm32mp157/rootfs NFS root fliesystem: /home/developer/projects/nfs/rootfs Linux source code: /home/developer/projects/linux-5.4.31 Device tree: /home/developer/projects/linux-5.4.31/arch/arm/boot/dts/stm32mp157-a ...

As the kernel runs, physical memory becomes increasingly fragmented. Certain devices, such as those using DMA, require large contiguous physical memory blocks. When such memory is unavailable at runtime, the device may fail to operate. To address this, Linux provides a mechanism to reserve a dedicated region of physical memory for specific devi ...

In the Linux kernel, the current macro provides a convenient way to access the task_struct instance representing the currently executing process or thread on a given CPU. This mechanism is essential for kernel code that needs to inspect or modify attributes of the running task. The task_struct is a central data structure in the kernel, encapsul ...

Binary Decomposition PrincipleAny positive integer can be decomposed into a sum of distinct powers of two (2n, where n ≥ 0). This mathematical property, which forms the foundation of binary representation, is the core mechanism leveraged by the Buddy allocation system.Kernel Buddy System Data Structure HierarchyThe architecture of the Buddy sys ...

eventfd(2) Combined with seelect(2) Source Code Analysis The code examples are from Linux kernel 4.17 eventfd(2) - Creates a file descriptor for event notification. Usage Source Code Analysis References #include <sys/eventfd.h> int eventfd(unsigned int initval, int flags); int eventfd2(unsigned int initval, int flags); Parameters - \ ...

Understanding the Platform Bus The platform bus is a virtual bus within the Linux kernel architecture, designed to unify the device and driver model. Unlike physical buses such as PCI or USB, the platform bus does not correspond to any physical hardware. It exists to manage devices that do not naturally fit into other bus models, ensuring a con ...

This analysis is based on Linux kernel 4.19.195. Software Implementation Principles The RCU implementation in software revolves around idnetifying the beginning of a Grace Period (GP), detecting Quiescent States (QS), determining when a grace period ends, handling post-grace-period cleanup, and initiating the next grace period—a large state mac ...

Character Device Driver Foundations Developing a Linux character device driver generally follows a standard sequence of operations: Acquire a major device number, either statically assigned or dynamically allocated by the kernel. Declare a file_operations structure to define the driver's supported interactions. Implement the requisite handlers ...