path: root/skey.c

#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>
#include <linux/input.h>
#include "keymap.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 1
/*
 * On the prototype model, the diodes were soldered backwards, so that the
 * negative ends were facing the cpins.
 * as outputs they seem to opendrain(transistor to high, resistor to low)
 * this means that the cpins can not pull the rlabels down. we can not
 * work around this by using the pins as active_low
 * we now have to use rpins as the output and cpins as the input because
 * we can only use active_high, and the positive side of the diodes are
 * facing the rpins. This means we don't have short-circuit since the diodes
 * are still connected to the cpins. however, when shorting them in
 * production it seems that the problem is not bad enough to cause the board
 * to shut down.
 */



/*
 * GPIO pins
 * Unsigned ints containing the BCM pin numbers for the pins used, __initdata
 * helps with the loading and unloading of data in memory
 */
static unsigned int column_pins[10] = {10, 24, 23, 22, 27, 18, 17, 15, 14, 4};
static unsigned int row_pins[3] = {3, 6, 5};
/*
 * GPIO labels
 */
static char * clabels[10] = {"C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9",};
static char * rlabels[3] = {"R0", "R1", "R2"};
/*
 * task struct for setting up the thread
 */

static struct task_struct *update_task;
/*
 * input.h input device
 */
struct input_dev * skey_dev;
/*
 * Name and ID, for use with input.h
 */
struct input_id skey_id;
char * skey_name = "Switch Keyboard for the Omnicom";
/*
 * Array to hold the keystate for the board
 * a char is assumed to be atleast 8 bits, the bit KEYSTATE_PHYS holds the previous physical
 * states for detecting rising and falling edges whereas the other ones hold the previous states
 * of the 3 keymaps when stickymode is turned on.
 */
char keystate[3][10]= {0};
#define KEYSTATE_PHYS 0x1
#define KEYSTATE_ALPHA 0x2
#define KEYSTATE_NUMBER 0x4
#define KEYSTATE_SPECIAL 0x8
/*
 * current keymapping,\
 * 0 - ALPHA
 * 1 - NUM
 * 2 - SPECIAL
 * 3 - SPECIAL with mouse
 */
int current_keymap = 0;
/*
 * Stickymode 
 */
int stickymode = 0;
//number of pixels mousemove buttons do
#define MOUSE_DIST 5
//same but for scrollwheel
#define WHEEL_DIST 5
/*
 * clears the state of stickymode keystates, sends a key up event if it was previously pressed
 * 
 */
void clearkeystate(void) {
	int row_index = 0;
	int column_index = 0;
	int map_index = 0; //range of 0 to 2, which are KEYSTATE_ALPHA to KEYSTATE_SPECIAL
	int keystate_mask; // the actual map used
	while (map_index < 3) {
		//gets mask from map_index
		switch(map_index) {
			case 0:
				keystate_mask = KEYSTATE_ALPHA;
			break;
			case 1:
				keystate_mask = KEYSTATE_NUMBER;
			break;
			case 2:
				keystate_mask = KEYSTATE_SPECIAL;
			break;
		}
		row_index = 0;
		while (row_index < 3) {
			column_index = 0;
			while (column_index < 10) {	
				//sends a button released event if it is not sticky mode
				if (keystate[row_index][column_index] & keystate_mask) {
					//reports key up
					input_report_key(skey_dev, skey_keymap[map_index][row_index][column_index], 0);
					input_sync(skey_dev);
					//sets the bit to low.
					keystate[row_index][column_index] = (~keystate_mask) & keystate[row_index][column_index];
				}
				column_index++;
			}
			row_index++;
		}
		map_index++;
	}
	return;
}
/*
 * The keystates are processed as following, the current read value is compared with the
 * previous one stored in KEYSTATE_PHYS to detect a rising or falling edge. for regular keys, 
 * the corresponding keycode from skey_keymap is sent, with the current_keymap. if stickymode 
 * is on, then it toggles the value stored in KEYSTATE_ALPHA, *NUMBER or *SPECIAL depending on
 * current_keymap. special keys that change the keymap and the mouse position are only triggered
 * on rising level, when current_keymap is 3, or special map with mouse, the KEYSTATE_SPECIAL
 * mask is used.
 */
/*
 * This function is called by skey_update_thread every time it reads the keyboard, and
 * implements the above. returns -EINVAL if the column and row are out of bouns, but that's
 * not going to happen.
 */
int processkey(int row, int column, int state) {
	//sanity checks
	if ((column < 10) && (column >= 0) && (row < 3) && (row >= 0)) {
	} else {
		/*if this happens, whatever is calling this function is not expected to handle
		 * this
		 */
		printk(KERN_ALERT "skey: keypress data sent to processkey() was invalid\n");
		return -EINVAL;
	}
	//finds the KEYSTATE_* bitmask to use with the current keymapping
	int keystate_bitmask;
	switch (current_keymap) {
		case 0:
			keystate_bitmask = KEYSTATE_ALPHA;
		break;
		case 1:
			keystate_bitmask = KEYSTATE_NUMBER;
		break;
		case 2:
			keystate_bitmask = KEYSTATE_SPECIAL;
		break;
		case 3:
			keystate_bitmask = KEYSTATE_SPECIAL;
		break;
		//if current_keymap is out of range [0,3]
		default:
			return -EINVAL;
		break;
	}

	//falling edge
	if ((KEYSTATE_PHYS & keystate[row][column]) && !state) {
		//after the previous keystate is checked, it is updated
		if (state) {
			keystate[row][column] = KEYSTATE_PHYS | keystate[row][column];
		} else {
			keystate[row][column] = (~KEYSTATE_PHYS) & keystate[row][column];
		}
		
		if (!stickymode) {
			//reports key up
			input_report_key(skey_dev, skey_keymap[current_keymap][row][column], 0);
			input_sync(skey_dev);

		}
	//rising edge
	}else if (!(KEYSTATE_PHYS & keystate[row][column]) && state) {
		//after the previous keystate is checked, it is updated
		if (state) {
			keystate[row][column] = KEYSTATE_PHYS | keystate[row][column];
		} else {
			keystate[row][column] = (~KEYSTATE_PHYS) & keystate[row][column];
		}
		/*
		 *handles keys that have special behavior, and to which stickykey do not apply
		 * if sticky keys don't apply then only the falling edge applies
		 */
		switch (skey_keymap[current_keymap][row][column]) {
			case KEY_ALPHAMAP:
				current_keymap = 0;
				return 0;
			break;
			case KEY_NUMBERMAP:
				current_keymap = 1;
				return 0;
			break;
			case KEY_SPECIALMAP:
				current_keymap = 2;
				return 0;
			break;
			case KEY_STICKYMAP:
				stickymode = !stickymode;
				if (!stickymode) {
					clearkeystate();
				}
				return 0;
			break;
			case KEY_MS_2ND:
				if (current_keymap == 2) {
					current_keymap = 3;
				} else if (current_keymap == 3) {
					current_keymap = 2;
				}
				return 0;
			break;
			case MS_UP:
				input_event(skey_dev, EV_REL, REL_Y, +MOUSE_DIST);
				input_sync(skey_dev);
				return 0;
			break;
			case MS_DOWN:
				input_event(skey_dev, EV_REL, REL_Y, -MOUSE_DIST);
				input_sync(skey_dev);
				return 0;
			break;	
			case MS_LEFT:
				input_event(skey_dev, EV_REL, REL_X, -MOUSE_DIST);
				input_sync(skey_dev);
				return 0;
			break;
			case MS_RIGHT:
				input_event(skey_dev, EV_REL, REL_X, +MOUSE_DIST);
				input_sync(skey_dev);
				return 0;
			break;
			case MS_SCRL_UP:
				input_event(skey_dev, EV_REL, REL_WHEEL, +WHEEL_DIST);
				input_sync(skey_dev);
				return 0;
			break;
			case MS_SCRL_DOWN:
				input_event(skey_dev, EV_REL, REL_WHEEL, -WHEEL_DIST);
				input_sync(skey_dev);
				return 0;
			break;
			}
		//if it's stickymode, toggle the state  stored and send corresponding vent
		if (stickymode) {
			//it was high before, so now it's being toggled off
			if (keystate[row][column] & keystate_bitmask) {
				input_report_key(skey_dev, skey_keymap[current_keymap][row][column], 0);
				input_sync(skey_dev);

				keystate[row][column] = (~keystate_bitmask) & keystate[row][column];
			//it was low before, so now it's being toggled on
			} else {
				input_report_key(skey_dev, skey_keymap[current_keymap][row][column], 1);
				input_sync(skey_dev);
				keystate[row][column] = keystate_bitmask | keystate[row][column];

			}
		//otherwise just send a key down event
		} else {
			input_report_key(skey_dev, skey_keymap[current_keymap][row][column], 1);
			input_sync(skey_dev);
		}
	}
	return 0;
}

/*
 *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
	//thread priority
	const struct sched_param PARAM = { .sched_priority = 45};
	//sets the thread to be kinda realtime
	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");
	}

	while (1) {
		if (USE_GPIO) {
			//reads the keyboard
			int row_index = 0;
			int column_index = 0;
			while (row_index < 3) {
				//sets the column pin high for reading
				gpio_set_value_cansleep(row_pins[row_index], 1);
				//gives it some buffer time
				usleep_range(10,10);
				//reads with all the rows
				column_index = 0;
				while (column_index < 10) {
					if (gpio_get_value_cansleep(column_pins[column_index])) {
						processkey(row_index, column_index, 1);
					} else {
						processkey(row_index, column_index, 0);
					}
					column_index++;
				}
				//sets the row pin low
				gpio_set_value_cansleep(row_pins[row_index], 0);
				usleep_range(10,10);
				row_index++;
			}
		}
		//sleep 500us= .5ms = 0.0005 seconds
		// 1 / 0.0005 = 2000 hz	fastest, but it's really 1/0.00052
		usleep_range(500,500);
		//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_IN ,clabels[i])) {
				printk(KERN_ALERT "skey: column_pins[%d], BCM %d request failed\n", i, column_pins[i]);
				return -EINVAL;
			}
			if (gpio_direction_input(column_pins[i])) {
				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_OUT_INIT_LOW ,rlabels[j])) {
				printk(KERN_ALERT "skey: row_pins[%d], BCM %d request failed\n", j, row_pins[j]);
				return -EINVAL;
			}
			if (gpio_direction_output(row_pins[j], 0)) {
				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 input.h device
	 */
	skey_dev = input_allocate_device();
	if (!skey_dev) {
		printk(KERN_ALERT "skey: unable to allocate input device\n");
		return -ENOMEM;
	}
	// declares the event code and typesthe device emmits
	set_bit(EV_KEY, skey_dev->evbit);
	set_bit(EV_REL, skey_dev->evbit);
	set_bit(KEY_CAPSLOCK, skey_dev->keybit);
	/*
	 * skey_dev->name and skey_dev->id are metadata that are required for X11
	 * and libinput to use skey_dev
	 */
	//sets the name of skey_dev
	skey_dev->name = skey_name;
	//sets ids
	skey_id.bustype = BUS_HOST;
	skey_id.vendor = 13398;
	skey_id.product = 13398;
	skey_id.version = 1;
	skey_dev->id = skey_id;
	// registers the device
	if (input_register_device(skey_dev)) {
		input_free_device(skey_dev);
		return -EINVAL;
	}
	//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");
	//explicitly sets pin 4 and 15 to be inputs.
	gpio_direction_input(4);
	gpio_direction_input(15);
	gpio_set_value_cansleep(4, 0);
	gpio_set_value_cansleep(15, 0);
	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);
	//frees input device
	input_free_device(skey_dev);
	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");