docs: add file headers

clients/cpu_temp/src/cpu_temp.c

+/*
+ * cpu_temp.c - Reads CPU temperature and sends it via message queue
+ *
+ * This client reads the CPU temperature from
+ * `/sys/class/thermal/thermal_zone0/temp`, converts it, and sends it as a
+ * floating-point measurement using a message queue.
+ *
+ * Usage:
+ *   ./cpu_temp <id> <delay_ms>
+ *
+ * Parameters:
+ *   <id>        - Unique identifier for the measurement
+ *   <delay_ms>  - Delay between measurements in milliseconds
+ *
+ * Example:
+ *   ./cpu_temp 1 250
+ */
+
 #include "../../../common/include/measurement.h"
 #include "../../../common/include/userspace_comm.h"
 #include <errno.h>

clients/dummy/src/dummy.c

+/*
+ * dummy_client.c - Generates sine wave data and sends it via message queue
+ *
+ * This client simulates sensor data by generating a sine wave value and
+ * sending it as a floating-point measurement using a message queue.
+ *
+ * Usage:
+ *   ./dummy <id> <delay_ms>
+ *
+ * Parameters:
+ *   <id>        - Unique identifier for the measurement
+ *   <delay_ms>  - Delay between measurements in milliseconds
+ *
+ * Example:
+ *   ./dummy 1 250
+ */
+
 #include "../../../common/include/measurement.h"
 #include "../../../common/include/userspace_comm.h"
 #include <errno.h>

clients/mem_usage/src/mem_usage.c

+/*
+ * mem_usage.c - Reads memory usage and sends it via message queue
+ *
+ * This program reads memory information using the `sysinfo` system call,
+ * calculates the used memory, and sends it as an unsigned integer measurement
+ * via a message queue.
+ *
+ * Usage:
+ *   ./mem_usage <id> <delay_ms>
+ *
+ * Parameters:
+ *   <id>        - Unique identifier for the measurement
+ *   <delay_ms>  - Delay between measurements in milliseconds
+ *
+ * Example:
+ *   ./mem_usage 1 250
+ */
+
 #include "../../../common/include/measurement.h"
 #include "../../../common/include/userspace_comm.h"
 #include <errno.h>

common/include/measurement.h

+/*
+ * measurement.h - Defines data structures and types for measurement handling
+ *
+ * This header file provides type definitions and structures for representing
+ * measurement data.
+ */
+
 #pragma once
 
 #if defined(__KERNEL__)

common/include/userspace_comm.h

+/*
+ * userspace_comm.h - Message queue communication for sending userspace
+ * measurement data
+ *
+ * This header file provides functions and structures for message queue
+ * interprocess communication. It allows sending measurement data from userspace
+ * applications.
+ */
+
 #pragma once
 
 #include "measurement.h"

common/src/measurement.c

+/*
+ * measurement.c - Implementation of measurement functions
+ *
+ * This file provides the implementation of the functions declared in
+ * measurement.h.
+ */
+
 #include "../include/measurement.h"
 
 size_t measurement_data_type_size(measurement_data_type_t type) {

common/src/userspace_comm.c

+/*
+ * userspace_comm.c - Implementation of message queue communication functions
+ *
+ * This file provides the implementation of the functions declared in
+ * userspace_comm.h.
+ *
+ */
+
 #include "../include/userspace_comm.h"
 #include <sys/ipc.h>
 #include <sys/msg.h>

daemon/include/receive.h

+/*
+ * receive.h - Message queue communication for receiving userspace measurement
+ * data
+ *
+ * This header file provides functions and structures for message queue
+ * interprocess communication. It allows receiving measurement data from
+ * userspace applications.
+ */
+
 #pragma once
 
 #include "../../common/include/measurement.h"

daemon/include/send.h

+/*
+ * send.h - Communication with the kernel device for measurement data
+ *
+ * This header file provides functions and structures to send measurement data
+ * to the kernel through the `/dev/sibyl` device.
+ */
+
 #pragma once
 
 #include "../../common/include/measurement.h"

daemon/src/main.c

+/*
+ * main.c - Daemon for receiving, processing, and sending measurement data
+ *
+ * This file implements a daemon that receives measurement data from a userspace
+ * message queue, processes the data, and sends it to the kernel via a character
+ * device.
+ *
+ * The daemon continuously runs in an infinite loop, receiving measurement data
+ * from userspace through a message queue. Upon receiving each measurement, it
+ * processes and compares the data with cached values to detect any updates or
+ * changes. If any updates are found, the daemon sends the new data to the
+ * kernel module.
+ */
+
 #include "../../common/include/measurement.h"
 #include "../../common/include/userspace_comm.h"
 #include "../include/receive.h"

daemon/src/receive.c

+/*
+ * receive.c - Implementation of message queue communication functions
+ *
+ * This file provides the implementation of the functions declared in
+ * receive.h.
+ *
+ */
+
 #include "../include/receive.h"
 #include "../../common/include/measurement.h"
 #include "../../common/include/userspace_comm.h"

daemon/src/send.c

+/*
+ * send.c - Implementation for sending measurement data to the kernel
+ *
+ * This file provides the implementation of the functions declared in
+ * send.h.
+ *
+ */
+
 #include "../include/send.h"
 #include <fcntl.h>
 #include <unistd.h>

kernel/kmod.c

+/*
+ * kmod.c - Kernel module for receiving, processing, and sending measurement
+ * data
+ *
+ * This kernel module provides functionality to communicate with userspace by
+ * receiving measurement data, preparing it for transmission, and sending it
+ * via GPIO pins at a specified baud rate. It integrates with a userspace
+ * application through a character device interface.
+ *
+ * The module operates in fixed time slots for data transmission, managed by a
+ * high-resolution timer. Upon receiving data from userspace, the module
+ * calculates a CRC checksum, prepares the data packet, and writes it into a
+ * send buffer. This data preparation occurs outside of the time slot but is
+ * triggered when new data is written to the device.
+ *
+ * The transmission itself happens in fixed time slots. The high-resolution
+ * timer triggers regular intervals, and during each time slot, when it's the
+ * systems turn, the data stored in the send buffer is transmitted bit-by-bit
+ * using GPIO, simulating UART-like communication with start and stop bits.
+ */
+
 #include "../common/include/measurement.h"
 #include <linux/cdev.h>
 #include <linux/crc32.h>