ezscroll/ezscroll.c at master · MatusGuy/ezscroll · GitHub

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#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/kbd_kern.h>
#include <linux/libps2.h>
#include <linux/kprobes.h>
#include <linux/serio.h>
#include <linux/input.h>
#include <linux/types.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("MatusGuy");

// NOTE: I'm not sure if this works with the EZ-7000 but
// there exists a driver on Windows that supports both
// and I'm assuming it's using the same method...
MODULE_DESCRIPTION("Trust EZ-7000/8000 Keyboard Scroll Wheel driver");

static struct kprobe kp;
static struct input_dev* scrdev;
static bool extended = false;

/* Pre-handler: Executed before the probed instruction is run */
static int ezscroll_ps2_pre_handler(struct kprobe* p, struct pt_regs* regs)
{
	//struct serio* serio = (struct serio*) regs->di;   // First argument: struct serio *serio
	u8 data = (u8) regs->si;                          // Second argument: u8 data
	//unsigned int flags = (unsigned int) regs->dx;     // Third argument: unsigned int flags

	//pr_info("Kprobe hit: ps2_interrupt function called\n");
	//pr_info("Serio struct address: %p\n", serio);
	//pr_info("Data received: 0x%02x\n", data);
	//pr_info("Flags: 0x%x\n", flags);

	if (data == 0xe0)
	{
		/// Next byte should be an extended key
		extended = true;
	}
	else if (extended)
	{
		u8 code = data & 0x7f;
		bool pressed = !(data >> 7);

		if (code == 0x0b)
		{
			input_report_rel(scrdev, REL_WHEEL, pressed ? 1 : -1);
			input_sync(scrdev);
		}
		else if (code == 0x16)
		{
			input_report_key(scrdev, BTN_MIDDLE, pressed);
			input_sync(scrdev);
		}

		extended = false;
	}

	return 0;
}

/* Module initialization */
static int __init ezscroll_init(void)
{
	int ret;

	scrdev = input_allocate_device();
	if (!scrdev) {
		printk(KERN_ERR "ezscroll_init: Error on input_allocate_device!\n");
		return -ENOMEM;
	}

	scrdev->name = "Trust EZ-7000/8000 Keyboard Scroll Wheel";
	scrdev->id.bustype = BUS_VIRTUAL;
	scrdev->id.vendor  = 0x0000;
	scrdev->id.product = 0x0000;
	scrdev->id.version = 0x0000;

	/// Declare what kind of inputs will be sent
	scrdev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
	scrdev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_MIDDLE);
	scrdev->relbit[0] = BIT_MASK(REL_WHEEL);

	ret = input_register_device(scrdev);
	if (ret < 0) {
		printk(KERN_ERR "ezscroll_init: Failed to register input device\n");
		return ret;
	}

	/// Use kprobes to hook to the ps2 interrupt function.
	kp.symbol_name = "ps2_interrupt";
	kp.pre_handler = ezscroll_ps2_pre_handler;

	ret = register_kprobe(&kp);
	if (ret < 0) {
		pr_err("Failed to register kprobe: %d\n", ret);
		return ret;
	}

	return 0;
}

/* Module cleanup */
static void __exit ezscroll_exit(void)
{
	input_unregister_device(scrdev);
	unregister_kprobe(&kp);
}

module_init(ezscroll_init);
module_exit(ezscroll_exit);