initial commit

Kconfig

@@ -0,0 +1,4 @@
+config GPIO_KEYBOARD_DRIVER
+	tristate "gpio-keyboard-driver"
+	help
+	  TODO write this

Makefile

@@ -0,0 +1,13 @@
+# Makefile for building my_driver kernel module
+
+KERNEL_DIR ?= $(PWD)
+KERNEL_BUILD ?= $(KERNEL_DIR)/build
+
+obj-m += gpio-keyboard-driver.o
+
+# The default target
+all:
+	$(MAKE) -C $(KERNEL_BUILD) M=$(PWD) modules
+
+clean:
+	$(MAKE) -C $(KERNEL_BUILD) M=$(PWD) clean

gpio-keyboard-driver.c

@@ -0,0 +1,117 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/gpio.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+
+static struct input_dev *input_device;
+static int gpio_button = -1;
+static int irq_number;
+
+// Interrupt handler when GPIO is asserted
+static irqreturn_t gpio_isr(int irq, void *dev_id)
+{
+    // Simulate keypress for the letter 'a'
+    input_report_key(input_device, KEY_A, 1);  // KEY_A is the keycode for 'a'
+    input_sync(input_device);  // Sync the event
+    input_report_key(input_device, KEY_A, 0);  // KEY_A release
+    input_sync(input_device);  // Sync again
+
+    return IRQ_HANDLED;
+}
+
+static int __init gpio_key_init(void)
+{
+    int ret;
+
+    // Parse the device tree to get the GPIO pin
+    struct device_node *node = of_find_node_by_path("/gpio_keys/button");
+    if (!node) {
+        pr_err("Device tree node not found\n");
+        return -ENODEV;
+    }
+
+    gpio_button = of_get_named_gpio(node, "gpio", 0);
+    if (gpio_button < 0) {
+        pr_err("Failed to get GPIO from device tree\n");
+        return gpio_button;
+    }
+
+    // Request the GPIO
+    ret = gpio_request(gpio_button, "gpio_key");
+    if (ret) {
+        pr_err("Failed to request GPIO\n");
+        return ret;
+    }
+
+    // Set the GPIO as input
+    ret = gpio_direction_input(gpio_button);
+    if (ret) {
+        pr_err("Failed to set GPIO as input\n");
+        gpio_free(gpio_button);
+        return ret;
+    }
+
+    // Get the interrupt number associated with this GPIO
+    irq_number = gpio_to_irq(gpio_button);
+    if (irq_number < 0) {
+        pr_err("Failed to get IRQ number for GPIO\n");
+        gpio_free(gpio_button);
+        return irq_number;
+    }
+
+    // Request IRQ
+    ret = request_irq(irq_number, gpio_isr, IRQF_TRIGGER_FALLING, "gpio_key_isr", NULL);
+    if (ret) {
+        pr_err("Failed to request IRQ\n");
+        gpio_free(gpio_button);
+        return ret;
+    }
+
+    // Register input device (keyboard emulator)
+    input_device = input_allocate_device();
+    if (!input_device) {
+        pr_err("Failed to allocate input device\n");
+        free_irq(irq_number, NULL);
+        gpio_free(gpio_button);
+        return -ENOMEM;
+    }
+
+    input_device->name = "GPIO Keyboard";
+    input_device->id.bustype = BUS_USB;
+    input_device->evbit[0] = BIT(EV_KEY);
+    input_device->keybit[BIT_WORD(KEY_A)] = BIT(KEY_A);
+
+    ret = input_register_device(input_device);
+    if (ret) {
+        pr_err("Failed to register input device\n");
+        input_free_device(input_device);
+        free_irq(irq_number, NULL);
+        gpio_free(gpio_button);
+        return ret;
+    }
+
+    pr_info("GPIO keyboard driver loaded\n");
+    return 0;
+}
+
+static void __exit gpio_key_exit(void)
+{
+    // Free resources
+    input_unregister_device(input_device);
+    free_irq(irq_number, NULL);
+    gpio_free(gpio_button);
+
+    pr_info("GPIO keyboard driver unloaded\n");
+}
+
+module_init(gpio_key_init);
+module_exit(gpio_key_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Nicholas Mello");
+MODULE_DESCRIPTION("GPIO Keyboard Driver");