#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/timer.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/sched.h>
/*
 * defines whether to access the gpios so other parts of the kernel module can
 * be tested on systems w/o the prerequisite GPIOs
 */
#define USE_GPIO 0
/*
 * Unsigned ints containing the BCM pin numbers for the pins used, __initdata
 * helps with the loading and unloading of data in memory
 */
static __initdata unsigned int column_pins[10] = {10, 24, 23, 22, 27, 18, 17, 15, 14, 4};
static __initdata unsigned int row_pins[3] = {3, 6, 5};
/*
 * GPIO labels
 */
static __initdata char * clabels[10] = {"C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9",};
static __initdata char * rlabels[3] = {"R0", "R1", "R2"};
/*
 * variables for setting up the thread
 */

static struct task_struct *update_task;
/*
 *This function is called every timer-period to actually read the keyboard
 */
int skey_update_thread (void *data) {
	printk(KERN_INFO "skey: starting update thread\n");
	//thread stuff
	const struct sched_param PARAM = { .sched_priority = 45};
	sched_setscheduler(current, SCHED_FIFO, &PARAM);
	printk(KERN_INFO "skey: started update thread\n");
	if (!USE_GPIO) {
		printk(KERN_ALERT "skey: currently in test mode with gpio use disabled\n");
	}
	//a counter for testing prints
	int i = 0;
	while (1) {
		i++;
		i = i % 500;
		if (!i) {
			printk(KERN_INFO "skey: update thread printed to kernel log every 1s\n");
		}
		if (USE_GPIO) {
			//reads the keyboard
			int row_index = 0;
			int column_index = 0;
			while (column_index < 10) {
				//sets the column pin high for reading
				gpio_set_value(column_pins[column_index], 1);
				//reads with all the rows
				row_index = 0;
				while (row_index < 3) {
					if (gpio_get_value(row_pins[row_index])) {
						printk(KERN_INFO "skey: key pressed at column %d, row %d\n", column_index, row_index);
					}
					row_index++;
				}
				//sets the row pin low
				gpio_set_value(column_pins[column_index], 0);
				column_index++;
			}
		}
		//sleep 2000us= 2ms = 0.002 seconds
		usleep_range(2000, 2000);	
		//for when the thread has to stop
		if (kthread_should_stop()) {
			 break;
		}
	}
	return 0;
}
/*
 * This function is called when the module is loaded
 * __init functions similar to __initdata
 */
static int  __init skey_init (void) {
	printk(KERN_INFO "skey: module initiating...\n");
	if (USE_GPIO) {
		int i = 0;
		//claims the column pins
		while (i < 10) {
			//checks to see if the gpios are valid
			if (!gpio_is_valid(column_pins[i])) {
				printk(KERN_ALERT "skey: column_pins[%d], BCM %d request invalid\n", i, column_pins[i]);
				return -EINVAL;
			}
			//requests access of the GPIO
			if (gpio_request_one(column_pins[i], GPIOF_OUT_INIT_LOW ,clabels[i])) {
				printk(KERN_ALERT "skey: column_pins[%d], BCM %d request failed\n", i, column_pins[i]);
				return -EINVAL;
			}
			if (gpio_direction_output(column_pins[i], 0)) {
				printk(KERN_ALERT "skey: column_pins[%d], BCM %d, set output failed\n",i, column_pins[i]);
			}
			i++;
		}
		//ditto for row pins
		int j = 0;
		while (j < 3) {
			//checks to see if the gpios are valid
			if (!gpio_is_valid(row_pins[j])) {
				printk(KERN_ALERT "skey: row_pins[%d], BCM %d request invalid\n", j, row_pins[j]);
				return -EINVAL;
			}
			//requests access of the GPIO
			if (gpio_request_one(row_pins[j], GPIOF_DIR_IN ,rlabels[j])) {
				printk(KERN_ALERT "skey: row_pins[%d], BCM %d request failed\n", j, row_pins[j]);
				return -EINVAL;
			}
			if (gpio_direction_input(row_pins[j])) {
				printk(KERN_ALERT "skey: row_pins[%d], BCM %d, set output failed\n",j, row_pins[j]);
			}
			j++;
		}
	} else {
		printk(KERN_ALERT "skey: currently in test mode with gpio use disabled\n");
	}
	//sets up update thread
	printk("skey: setting up update thread...\n");
	update_task = kthread_run(skey_update_thread, NULL, "skey_update_thread");
	printk(KERN_INFO "skey: module finished initiating\n");
	return 0;
}
/*
 * This function is called when the module is unloaded
 *
 */
static void __exit skey_exit (void) {
	printk(KERN_INFO "skey: module exiting...\n");
	if (USE_GPIO) {
		//frees column and row pins
		int i = 0;
		while (i < 10) {
			gpio_free(column_pins[i]);
			i++;
		}
		int j = 0;
		while (j < 3) {
			gpio_free(row_pins[j]);
			j++;
		}
	} else {
		printk(KERN_ALERT "skey: currently in test mode with gpio use disabled\n");
	}
	//deletes the thread
	kthread_stop(update_task);
	printk(KERN_INFO "skey: module exited\n");
	return;
}
/*
 * Registers the init and exit functions
 */
module_init(skey_init);
module_exit(skey_exit);
/*
 * registers module metadata
 */
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Haoran S. Diao <1339802534.kk@gmail.com>");
MODULE_DESCRIPTION("Driver for the omnicom switch keyboard");
/*
 *this sets the name of device files used by this module, this is used
 *when the kernel makes devices automatically
 */
MODULE_SUPPORTED_DEVICE("skeydev");