From 4eae56e36fc37d23d141ddee04cbcb75fbdc259f Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Thu, 15 Jun 2017 11:40:20 +0100
Subject: [PATCH] irq kind of works!

---
 kernel_module/irq.c | 57 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 14 deletions(-)

diff --git a/kernel_module/irq.c b/kernel_module/irq.c
index 2324e735..ab02ae4f 100644
--- a/kernel_module/irq.c
+++ b/kernel_module/irq.c
@@ -1,44 +1,73 @@
 /*
 TODO: get handler running multiple times on some existing interrupt from /proc/interrupts.
+
+Inside QEMU, try:
+
+	watch -n 1 cat /proc/interrupts
+
+Then see how clicking the mouse and keyboard affect the interrupts. This will point you to:
+
+- 1: keyboard
+- 12: mouse click and drags
+
+Likely this uses some old and simple serial interface that QEMU implements:
+USB mouses and keyboards are not that nice.
 */
 
+#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
+#include <linux/fs.h>
 #include <linux/interrupt.h>
-#include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 
+#define NAME "lkmc_character_device"
+
 MODULE_LICENSE("GPL");
 
+static int major;
+static int irq = 0;
+module_param_named(i, irq, int, S_IRUSR);
+MODULE_PARM_DESC(i, "irq line number");
+
 /**
  * Return value from kernel docs:*
  *
  * enum irqreturn
- * @IRQ_NON      interrupt was not from this device or was not handled
- * @IRQ_HANDLED  interrupt was handled by this device
+ * @IRQ_NONE        interrupt was not from this device or was not handled
+ * @IRQ_HANDLED     interrupt was handled by this device
  * @IRQ_WAKE_THREAD handler requests to wake the handler thread
  */
-static irqreturn_t handler(int i, void *v)
+static irqreturn_t handler(int irq, void *dev)
 {
-	pr_info("handler %llu\n", (unsigned long long)jiffies);
+	pr_info("handler irq = %d dev = %d\n", irq, *(int *)dev);
 	return IRQ_HANDLED;
 }
 
+static const struct file_operations fops;
+
 static int myinit(void)
 {
-	irqreturn_t r;
-	r = request_irq(
-		1,
-		handler,
-		IRQF_SHARED,
-		"myirqhandler0",
-		0
-	);
-	pr_info("request_irq %llu\n", (unsigned long long)r);
+	int ret;
+
+	major = register_chrdev(0, NAME, &fops);
+	for (int i = 0; i < 128; ++i) {
+		ret = request_irq(
+			i,
+			handler,
+			/* Requires an associated device. */
+			IRQF_SHARED,
+			"myirqhandler0",
+			&major
+		);
+		pr_info("request_irq irq = %d ret = %d\n", i, ret);
+	}
 	return 0;
 }
 
 static void myexit(void)
 {
+	free_irq(irq, NULL);
+	unregister_chrdev(major, NAME);
 }
 
 module_init(myinit)