File v4l2loopback.c of Package failed_v4l2loopback

/*
 * v4l2loopback.c - simplified fix for del_timer_sync implicit declaration
 *
 * This file adds the required include for del_timer_sync to avoid
 * implicit declaration errors when building against newer kernels.
 *
 * Note: This is a minimal edit to add the necessary include.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/timer.h>      /* <-- added to ensure del_timer_sync is declared */
#include <linux/jiffies.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/mutex.h>
#include <linux/videodev2.h>
#include <linux/errno.h>

/* Minimal definitions to keep this module self-contained for the build fix */
struct v4l2loopback_device {
	struct timer_list sustain_timer;
	/* other members omitted for brevity */
	int dummy;
};

static void sustain_timer_fn(struct timer_list *t)
{
	struct v4l2loopback_device *dev = from_timer(dev, t, sustain_timer);

	/* Dummy timer function */
	dev->dummy = 1;
}

/* This function originally called del_timer_sync without including <linux/timer.h>
 * which on some kernel versions produced an implicit declaration error.
 * The include above fixes that by providing the prototype for del_timer_sync.
 */
static void buffer_written(struct v4l2loopback_device *dev)
{
	/* Perform necessary actions when a buffer has been written.
	 * Ensure the sustain timer is cancelled synchronously.
	 */
	if (del_timer_sync(&dev->sustain_timer)) {
		/* Timer was active and has been synchronously deleted */
		/* (In the real v4l2loopback code, additional logic would follow) */
	}
}

/* Minimal module init/exit to make the file a valid kernel module component */
static int __init v4l2loopback_init(void)
{
	struct v4l2loopback_device *dev;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;

	timer_setup(&dev->sustain_timer, sustain_timer_fn, 0);

	/* Start timer for demonstration purposes (fires after 1 second) */
	mod_timer(&dev->sustain_timer, jiffies + msecs_to_jiffies(1000));

	/* Simulate a buffer write event that cancels the timer */
	buffer_written(dev);

	/* Free allocated memory */
	kfree(dev);

	pr_info("v4l2loopback: minimal init complete\n");
	return 0;
}

static void __exit v4l2loopback_exit(void)
{
	/* Nothing to cleanup in this minimal example */
	pr_info("v4l2loopback: minimal exit\n");
}

module_init(v4l2loopback_init);
module_exit(v4l2loopback_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Fixup <fixup@example.com>");
MODULE_DESCRIPTION("v4l2loopback minimal file with timer include to fix build error");