#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/string.h>

MODULE_LICENSE("GPL");

#define RELAY_K1 18
#define RELAY_K2 23
#define RELAY_K3 24
#define RELAY_K4 25

#define NO_OFF 0
#define NO_ON 1

static struct kobject *relay_kobject;

static ssize_t set_relay(struct kobject *kobj, struct kobj_attribute *attr, const char *buff, size_t count) {
	int relay = 0;
	u8 v = 0;
	sscanf(buff, "%hhd", &v);

	if (strcmp(attr->attr.name, "relay1") == 0) {
		relay = RELAY_K1;
	} else if (strcmp(attr->attr.name, "relay2") == 0) {
		relay = RELAY_K2;
	} else if (strcmp(attr->attr.name, "relay3") == 0) {
		relay = RELAY_K3;
	} else if (strcmp(attr->attr.name, "relay4") == 0) {
		relay = RELAY_K4;
	}

	gpio_set_value(relay, (v == 0) ? NO_OFF : NO_ON);
	return count;
}

static ssize_t get_relay(struct kobject *kobj, struct kobj_attribute *attr, char *buff) {
	int relay = 0;
	if (strcmp(attr->attr.name, "relay1") == 0) {
		relay = RELAY_K1;
	} else if (strcmp(attr->attr.name, "relay2") == 0) {
		relay = RELAY_K2;
	} else if (strcmp(attr->attr.name, "relay3") == 0) {
		relay = RELAY_K3;
	} else if (strcmp(attr->attr.name, "relay4") == 0) {
		relay = RELAY_K4;
	}
	return sprintf(buff, "%d", gpio_get_value(relay));
}

static struct kobj_attribute relay1_attribute = __ATTR(relay1, (S_IWUSR | S_IRUGO), get_relay, set_relay);
static struct kobj_attribute relay2_attribute = __ATTR(relay2, (S_IWUSR | S_IRUGO), get_relay, set_relay);
static struct kobj_attribute relay3_attribute = __ATTR(relay3, (S_IWUSR | S_IRUGO), get_relay, set_relay);
static struct kobj_attribute relay4_attribute = __ATTR(relay4, (S_IWUSR | S_IRUGO), get_relay, set_relay);

static int __init relay_init(void) {
	gpio_request(RELAY_K1, "RELAY_K1");
	gpio_request(RELAY_K2, "RELAY_K2");
	gpio_request(RELAY_K3, "RELAY_K3");
	gpio_request(RELAY_K4, "RELAY_K4");

	gpio_direction_output(RELAY_K1, NO_ON);
	gpio_direction_output(RELAY_K2, NO_ON);
	gpio_direction_output(RELAY_K3, NO_ON);
	gpio_direction_output(RELAY_K4, NO_ON);

	relay_kobject = kobject_create_and_add("relay", NULL);

	if (sysfs_create_file(relay_kobject, &relay1_attribute.attr)) {
		pr_debug("failed to create relay1 sysfs!\n");
	}
	if (sysfs_create_file(relay_kobject, &relay2_attribute.attr)) {
		pr_debug("failed to create relay2 sysfs!\n");
	}
	if (sysfs_create_file(relay_kobject, &relay3_attribute.attr)) {
		pr_debug("failed to create relay3 sysfs!\n");
	}
	if (sysfs_create_file(relay_kobject, &relay4_attribute.attr)) {
		pr_debug("failed to create relay4 sysfs!\n");
	}

	return 0;
}

static void __exit relay_exit(void) {
	kobject_put(relay_kobject);

	gpio_free(RELAY_K1);
	gpio_free(RELAY_K2);
	gpio_free(RELAY_K3);
	gpio_free(RELAY_K4);
}

module_init(relay_init);
module_exit(relay_exit);