Barebones working kernel driver

skeletton.c

@@ -0,0 +1,93 @@
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/gpio.h>
+
+// Operation prototypes
+static int dev_open(struct inode *, struct file *);
+
+int major;
+struct class *j_class;
+struct device *j_device;
+
+// The driver's file operations
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.open = dev_open
+};
+
+/**
+ * Driver initialization code. 
+ */
+static int __init mylab1_joystick_dev_init(void) {
+	// TODO
+	// 1) Register the device by dynamically obtaining a major number
+    major = register_chrdev(0, "mylab1_joystick", &fops);
+    if(major < 0){
+        pr_info("mylab1_joystick: could not get a major number, initialisation failed\n");
+        return -1;
+    }
+	// 2) Create the class
+    j_class = class_create("mylab1_joystick");
+    if (IS_ERR(j_class)){
+        pr_info("mylab1_joystick: could not create class, initialisation failed\n");
+        return -1;
+    }
+    // 3) Create the device in /dev
+    j_device = device_create(j_class, NULL, MKDEV(major, 0), NULL, "mylab1_joystick");
+    if (IS_ERR(j_device)){
+        pr_info("mylab1_joystick: could not create device, initialisation failed\n");
+        return -1;
+    }
+	// 6) Request the necessary GPIOs
+	// 7) Register an IRQ handler per GPIO
+	pr_info("mylab1_joystick: driver initialized\n");
+	return 0;
+}
+
+/**
+ * This function is called when the module is unloaded.
+ */
+static void __exit mylab1_joystick_dev_exit(void) {
+	// TODO
+	// 1) Destroy the device
+    device_destroy(j_class,MKDEV(major, 0));
+	// 2) Destroy the class
+    class_destroy(j_class);
+	// 4) Unregister the device
+    unregister_chrdev(major,"mylab1_joystick");
+	// 5) Free the IRQs
+	// 6) Free the GPIOs
+	pr_info("mylab1_joystick: driver destroyed\n");
+}
+
+/**
+ * Open operation
+ */
+static int dev_open(struct inode *inod, struct file *f) {
+	pr_info("mylab1_joystick: device opened\n");
+	return 0;
+}
+
+/**
+ * Joystick left IRQ handler
+ */
+/*
+static irqreturn_t mylab_left_irq_handler(int irq, void *dev_id) {
+	// TODO
+	// - Operations to be done when the left position of the joystick is triggered
+    // - At minimum, the joystick state must be updated
+	return (irqreturn_t) IRQ_HANDLED;  // Announce that the IRQ has been handled correctly
+}
+*/
+
+module_init(mylab1_joystick_dev_init);
+module_exit(mylab1_joystick_dev_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jaime Coder <maxime.rohmer@hesge.ch>");
+MODULE_DESCRIPTION("Module to drive the joystick on the myLab1 card");
+MODULE_VERSION("0.1");