#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/slab.h>


#include "mod.h"
#include "dev.h"
#include "debug.h"


MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Suren A. Chilingaryan <csa@suren.me>");
MODULE_DESCRIPTION("Kernel Memory Manager - a module to manipulate kernel memory");
MODULE_VERSION("0.0.1");

int kmm_minors = KMM_MINORS;

module_param(kmm_minors, int, S_IRUGO);


static dev_t kmm_devno;			/**< major number */
static kmm_dev_t **kmm_devs = NULL;	/**< per-device context */
static spinlock_t kmm_devs_lock;	/**< lock protecting creation/destruction of devices */
static struct class *kmm_class;		/**< device class */


static void kmm_module_cleanup(void)
{
    int i;

    if (kmm_devs) {
	for (i = 0; i < kmm_minors; i++) {
	    if (kmm_devs[i]) {
		if (kmm_devs[i]->dev)
		    device_destroy(kmm_class, kmm_devs[i]->devno);
		cdev_del(&kmm_devs[i]->cdev);
		kfree(kmm_devs[i]);
	    }
	}
	kfree(kmm_devs);
    }


    if (kmm_class)
    	class_destroy(kmm_class);

    unregister_chrdev_region(kmm_devno, kmm_minors);
}

static int kmm_module_setup_cdev(void)
{
    int i;
    int err = 0;
    dev_t devno;
    kmm_dev_t *dev;

    dev = kmalloc(sizeof(kmm_dev_t), GFP_KERNEL);
    if (!dev) {
	mod_info("Couldn't allocate memory. Device is not created.\n");
	return -ENOMEM;
    }

    cdev_init(&dev->cdev, kmm_get_fops());
    dev->cdev.owner = THIS_MODULE;
    dev->cdev.ops = kmm_get_fops();

    spin_lock(&kmm_devs_lock);
    for (i = 0; i < kmm_minors; i++) {
	if (!kmm_devs[i])
	    break;
    }

    if (i == kmm_minors) {
	mod_info("No free minor numbers left");
	err = -EBUSY;
	goto fail;
    }

    devno = MKDEV(MAJOR(kmm_devno), MINOR(kmm_devno) + i);
    dev->devno = devno;

    err = cdev_add(&dev->cdev, devno, 1);
    if (err) {
	mod_info("Error %d adding device kmm%d", err, i);
	goto fail;
    }

    dev->dev = device_create(kmm_class, NULL, devno, dev, KMM_NODE_FMT, MINOR(kmm_devno) + i);
    if (!dev->dev) {
	mod_info("Error creating /dev/%s%d\n", KMM_NODE, MINOR(kmm_devno) + i);
	goto fail;
    }
    dev_set_drvdata(dev->dev, dev);

    kmm_devs[i] = dev;
    spin_unlock(&kmm_devs_lock);

    mod_info("Device /dev/%s%d added\n", KMM_NODE, MINOR(kmm_devno) + i);

    return 0;

fail:
    spin_unlock(&kmm_devs_lock);
    kfree(dev);
    return err;
}

static int __init kmm_module_init(void)
{
    int err;

    spin_lock_init(&kmm_devs_lock);

    if ((err = alloc_chrdev_region(&kmm_devno, 0, kmm_minors, KMM_NODE))) {
	mod_info("Couldn't allocate chrdev region. Module not loaded.\n");
	goto alloc_chrdev_fail;
    }

    kmm_class = class_create(THIS_MODULE, KMM_NODE);
    if (IS_ERR(kmm_class)) {
	mod_info("No sysfs support. Module not loaded.\n");
	goto fail;
    }

    kmm_devs = kmalloc(kmm_minors * sizeof(kmm_dev_t*), GFP_KERNEL);
    if (!kmm_devs) {
	mod_info("Couldn't allocate memory. Module not loaded.\n");
	err = -ENOMEM;
    }
    memset(kmm_devs, 0, kmm_minors * sizeof(kmm_dev_t*));

    mod_info("Major %d allocated to node '%s'\n", MAJOR(kmm_devno), KMM_NODE);

    err = kmm_module_setup_cdev();
    if (err) goto fail;


    return 0;

fail:
    kmm_module_cleanup();
alloc_chrdev_fail:
    return err;
}


static void __exit kmm_module_exit(void)
{
    kmm_module_cleanup();
}

module_init(kmm_module_init);
module_exit(kmm_module_exit);