From edc26eca45203af812bf516c501458e20c1acaf2 Mon Sep 17 00:00:00 2001
From: Imbus <>
Date: Sat, 10 May 2025 09:30:07 +0200
Subject: [PATCH] GPIO code

---
 demo_module.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 5 deletions(-)

diff --git a/demo_module.c b/demo_module.c
index e43ae92..85598ab 100644
--- a/demo_module.c
+++ b/demo_module.c
@@ -1,6 +1,11 @@
-#include <linux/module.h>
-#include <linux/kernel.h>
+#include <linux/gpio/consumer.h>
 #include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+/*
+ * Last compiled with Linux 6.14.5-300.fc42.x86_64
+ */
 
 /* Meta Info */
 MODULE_DESCRIPTION("Demo kernel module.");
@@ -8,19 +13,61 @@ MODULE_VERSION("0.0.1");
 MODULE_AUTHOR("Imbus");
 MODULE_LICENSE("GPL");
 
+/*
+ * Hard coded for RPI3
+ * Usually retrieved via device tree
+ */
+#define IO_LED 21
+#define IO_BUTTON 20
+#define IO_OFFSET 0
+
+static struct gpio_desc *led, *button;
+
 /**
  * @brief Called on load
  */
 static int __init demo_mod_init(void) {
-    printk(KERN_INFO "Demo module loaded successfully...");
-    return 0;
+  printk(KERN_INFO "Demo module loaded successfully...");
+
+  int status;
+
+  led = gpio_to_desc(IO_LED + IO_OFFSET);
+  if (!led) {
+    printk("gpioctrl - Error getting pin 21\n");
+    return -ENODEV;
+  }
+
+  button = gpio_to_desc(IO_BUTTON + IO_OFFSET);
+  if (!button) {
+    printk("gpioctrl - Error getting pin 20\n");
+    return -ENODEV;
+  }
+
+  status = gpiod_direction_output(led, 0);
+  if (status) {
+    printk("gpioctrl - Error setting pin 20 to output\n");
+    return status;
+  }
+
+  status = gpiod_direction_input(button);
+  if (status) {
+    printk("gpioctrl - Error setting pin 21 to input\n");
+    return status;
+  }
+
+  gpiod_set_value(led, 1);
+
+  printk("gpioctrl - Button is %spressed\n",
+         gpiod_get_value(button) ? " " : "not ");
+
+  return 0;
 }
 
 /**
  * @brief Called on unload
  */
 static void __exit demo_mod_exit(void) {
-    printk(KERN_INFO "Demo module unloaded successfully...");
+  printk(KERN_INFO "Demo module unloaded successfully...");
 }
 
 module_init(demo_mod_init);