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To build a kernel module that emulates a real-time second-counter device using the Linux kernel’s timer infrastructure, follow these precise, production-ready steps. This implementation leverages struct timer_list, avoids deprecated APIs (e.g., setup_timer), and ensures thread-safe, interupt-context–compatible behavior. Step 1: Define the Devic ...

This example demonstrates how to implement a GPIO-controlled LED driver that ensures only one user process can access the LED at a time using a counting semaphore initialized to 1 (binary semaphore). The semaphore is acquired in the open() handler and released in the release() handler, effectively serializign access across multiple processes. D ...