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 +1,128 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/gpio.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/of_irq.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/platform_device.h>
+
+static struct input_dev *kbd_dev;
+static int gpio_num;
+static int irq_num;
+
+static irqreturn_t gpio_irq_handler(int irq, void *dev_id)
+{
+    int state = gpio_get_value(gpio_num);
+
+    /* Active low button */
+    if (state == 0) {
+        input_report_key(kbd_dev, KEY_A, 1);
+        input_sync(kbd_dev);
+    } else {
+        input_report_key(kbd_dev, KEY_A, 0);
+        input_sync(kbd_dev);
+    }
+
+    return IRQ_HANDLED;
+}
+
+static int gpio_kbd_probe(struct platform_device *pdev)
+{
+    int ret;
+
+    struct device *dev = &pdev->dev;
+    struct device_node *np = dev->of_node;
+
+    if (!np)
+        return -EINVAL;
+
+    /* Read GPIO from DT */
+    gpio_num = of_get_named_gpio(np, "gpios", 0);
+    if (gpio_num < 0) {
+        dev_err(dev, "Failed to get GPIO from DT\n");
+        return gpio_num;
+    }
+
+    ret = gpio_request(gpio_num, "gpio_kbd_button");
+    if (ret) {
+        dev_err(dev, "Failed to request GPIO\n");
+        return ret;
+    }
+
+    gpio_direction_input(gpio_num);
+
+    /* Allocate input device */
+    kbd_dev = input_allocate_device();
+    if (!kbd_dev) {
+        dev_err(dev, "Failed to allocate input device\n");
+        gpio_free(gpio_num);
+        return -ENOMEM;
+    }
+
+    kbd_dev->name = "GPIO Keyboard Device";
+    kbd_dev->evbit[0] = BIT_MASK(EV_KEY);
+    set_bit(KEY_A, kbd_dev->keybit);
+
+    ret = input_register_device(kbd_dev);
+    if (ret) {
+        dev_err(dev, "Failed to register input device\n");
+        input_free_device(kbd_dev);
+        gpio_free(gpio_num);
+        return ret;
+    }
+
+    /* Get IRQ from DT */
+    irq_num = of_irq_get(np, 0);
+    if (irq_num < 0) {
+        dev_err(dev, "Failed to get IRQ from DT\n");
+        input_unregister_device(kbd_dev);
+        gpio_free(gpio_num);
+        return irq_num;
+    }
+
+    ret = request_irq(irq_num,
+                      gpio_irq_handler,
+                      IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+                      "gpio_kbd_irq",
+                      NULL);
+
+    if (ret) {
+        dev_err(dev, "Failed to request IRQ\n");
+        input_unregister_device(kbd_dev);
+        gpio_free(gpio_num);
+        return ret;
+    }
+
+    dev_info(dev, "GPIO keyboard driver loaded\n");
+    return 0;
+}
+
+static void gpio_kbd_remove(struct platform_device *pdev)
+{
+    free_irq(irq_num, NULL);
+    input_unregister_device(kbd_dev);
+    gpio_free(gpio_num);
+}
+
+static const struct of_device_id gpio_kbd_of_match[] = {
+    { .compatible = "arcade,gpio-keyboard" },
+    { }
+};
+MODULE_DEVICE_TABLE(of, gpio_kbd_of_match);
+
+static struct platform_driver gpio_kbd_driver = {
+    .probe = gpio_kbd_probe,
+    .remove = gpio_kbd_remove,
+    .driver = {
+        .name = "gpio-keyboard",
+        .of_match_table = gpio_kbd_of_match,
+    },
+};
+
+module_platform_driver(gpio_kbd_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Nicholas Mello");
+MODULE_DESCRIPTION("GPIO-based virtual keyboard driver using Device Tree");