text: /*
   *  Parallel port to Walkera WK-0701 TX joystick
   *
   *  Copyright (c) 2008 Peter Popovec
   *
   *  More about driver:  <file:Documentation/input/walkera0701.txt>
   */
  
  /*
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published by
   * the Free Software Foundation.
  */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #define RESERVE 20000
  #define SYNC_PULSE 1306000
  #define BIN0_PULSE 288000
  #define BIN1_PULSE 438000
  
  #define ANALOG_MIN_PULSE 318000
  #define ANALOG_MAX_PULSE 878000
  #define ANALOG_DELTA 80000
  
  #define BIN_SAMPLE ((BIN0_PULSE + BIN1_PULSE) / 2)
  
  #define NO_SYNC 25
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/parport.h>
  #include <linux/input.h>
  #include <linux/hrtimer.h>
  
  MODULE_AUTHOR("Peter Popovec <popovec@fei.tuke.sk>");
  MODULE_DESCRIPTION("Walkera WK-0701 TX as joystick");
  MODULE_LICENSE("GPL");
  
  static unsigned int walkera0701_pp_no;
  module_param_named(port, walkera0701_pp_no, int, 0);
  MODULE_PARM_DESC(port,
  		 "Parallel port adapter for Walkera WK-0701 TX (default is 0)");
  
  /*
   * For now, only one device is supported, if somebody need more devices, code
   * can be expanded, one struct walkera_dev per device must be allocated and
   * set up by walkera0701_connect (release of device by walkera0701_disconnect)
   */
  
  struct walkera_dev {
  	unsigned char buf[25];
  	u64 irq_time, irq_lasttime;
  	int counter;
  	int ack;
  
  	struct input_dev *input_dev;
  	struct hrtimer timer;
  
  	struct parport *parport;
  	struct pardevice *pardevice;
  };
  
  static struct walkera_dev w_dev;
  
  static inline void walkera0701_parse_frame(struct walkera_dev *w)
  {
  	int i;
  	int val1, val2, val3, val4, val5, val6, val7, val8;
  	int magic, magic_bit;
  	int crc1, crc2;
  
  	for (crc1 = crc2 = i = 0; i < 10; i++) {
  		crc1 += w->buf[i] & 7;
  		crc2 += (w->buf[i] & 8) >> 3;
  	}
  	if ((w->buf[10] & 7) != (crc1 & 7))
  		return;
  	if (((w->buf[10] & 8) >> 3) != (((crc1 >> 3) + crc2) & 1))
  		return;
  	for (crc1 = crc2 = 0, i = 11; i < 23; i++) {
  		crc1 += w->buf[i] & 7;
  		crc2 += (w->buf[i] & 8) >> 3;
  	}
  	if ((w->buf[23] & 7) != (crc1 & 7))
  		return;
  	if (((w->buf[23] & 8) >> 3) != (((crc1 >> 3) + crc2) & 1))
  		return;
  	val1 = ((w->buf[0] & 7) * 256 + w->buf[1] * 16 + w->buf[2]) >> 2;
  	val1 *= ((w->buf[0] >> 2) & 2) - 1;	/* sign */
  	val2 = (w->buf[2] & 1) << 8 | (w->buf[3] << 4) | w->buf[4];
  	val2 *= (w->buf[2] & 2) - 1;	/* sign */
  	val3 = ((w->buf[5] & 7) * 256 + w->buf[6] * 16 + w->buf[7]) >> 2;
  	val3 *= ((w->buf[5] >> 2) & 2) - 1;	/* sign */
  	val4 = (w->buf[7] & 1) << 8 | (w->buf[8] << 4) | w->buf[9];
  	val4 *= (w->buf[7] & 2) - 1;	/* sign */
  	val5 = ((w->buf[11] & 7) * 256 + w->buf[12] * 16 + w->buf[13]) >> 2;
  	val5 *= ((w->buf[11] >> 2) & 2) - 1;	/* sign */
  	val6 = (w->buf[13] & 1) << 8 | (w->buf[14] << 4) | w->buf[15];
  	val6 *= (w->buf[13] & 2) - 1;	/* sign */
  	val7 = ((w->buf[16] & 7) * 256 + w->buf[17] * 16 + w->buf[18]) >> 2;
  	val7 *= ((w->buf[16] >> 2) & 2) - 1;	/*sign */
  	val8 = (w->buf[18] & 1) << 8 | (w->buf[19] << 4) | w->buf[20];
  	val8 *= (w->buf[18] & 2) - 1;	/*sign */
  
  	magic = (w->buf[21] << 4) | w->buf[22];
  	magic_bit = (w->buf[24] & 8) >> 3;
  	pr_debug("%4d %4d %4d %4d  %4d %4d %4d %4d (magic %2x %d)\n",
  		 val1, val2, val3, val4, val5, val6, val7, val8,
  		 magic, magic_bit);
  
  	input_report_abs(w->input_dev, ABS_X, val2);
  	input_report_abs(w->input_dev, ABS_Y, val1);
  	input_report_abs(w->input_dev, ABS_Z, val6);
  	input_report_abs(w->input_dev, ABS_THROTTLE, val3);
  	input_report_abs(w->input_dev, ABS_RUDDER, val4);
  	input_report_abs(w->input_dev, ABS_MISC, val7);
  	input_report_key(w->input_dev, BTN_GEAR_DOWN, val5 > 0);
  }
  
  static inline int read_ack(struct pardevice *p)
  {
  	return parport_read_status(p->port) & 0x40;
  }
  
  /* falling edge, prepare to BIN value calculation */
  static void walkera0701_irq_handler(void *handler_data)
  {
  	u64 pulse_time;
  	struct walkera_dev *w = handler_data;
  
  	w->irq_time = ktime_to_ns(ktime_get());
  	pulse_time = w->irq_time - w->irq_lasttime;
  	w->irq_lasttime = w->irq_time;
  
  	/* cancel timer, if in handler or active do resync */
  	if (unlikely(0 != hrtimer_try_to_cancel(&w->timer))) {
  		w->counter = NO_SYNC;
  		return;
  	}
  
  	if (w->counter < NO_SYNC) {
  		if (w->ack) {
  			pulse_time -= BIN1_PULSE;
  			w->buf[w->counter] = 8;
  		} else {
  			pulse_time -= BIN0_PULSE;
  			w->buf[w->counter] = 0;
  		}
  		if (w->counter == 24) {	/* full frame */
  			walkera0701_parse_frame(w);
  			w->counter = NO_SYNC;
  			if (abs(pulse_time - SYNC_PULSE) < RESERVE)	/* new frame sync */
  				w->counter = 0;
  		} else {
  			if ((pulse_time > (ANALOG_MIN_PULSE - RESERVE)
  			     && (pulse_time < (ANALOG_MAX_PULSE + RESERVE)))) {
  				pulse_time -= (ANALOG_MIN_PULSE - RESERVE);
  				pulse_time = (u32) pulse_time / ANALOG_DELTA;	/* overtiping is safe, pulsetime < s32.. */
  				w->buf[w->counter++] |= (pulse_time & 7);
  			} else
  				w->counter = NO_SYNC;
  		}
  	} else if (abs(pulse_time - SYNC_PULSE - BIN0_PULSE) <
  				RESERVE + BIN1_PULSE - BIN0_PULSE)	/* frame sync .. */
  		w->counter = 0;
  
  	hrtimer_start(&w->timer, ktime_set(0, BIN_SAMPLE), HRTIMER_MODE_REL);
  }
  
  static enum hrtimer_restart timer_handler(struct hrtimer
  					  *handle)
  {
  	struct walkera_dev *w;
  
  	w = container_of(handle, struct walkera_dev, timer);
  	w->ack = read_ack(w->pardevice);
  
  	return HRTIMER_NORESTART;
  }
  
  static int walkera0701_open(struct input_dev *dev)
  {
  	struct walkera_dev *w = input_get_drvdata(dev);
  
  	if (parport_claim(w->pardevice))
  		return -EBUSY;
  
  	parport_enable_irq(w->parport);
  	return 0;
  }
  
  static void walkera0701_close(struct input_dev *dev)
  {
  	struct walkera_dev *w = input_get_drvdata(dev);
  
  	parport_disable_irq(w->parport);
  	hrtimer_cancel(&w->timer);
  
  	parport_release(w->pardevice);
  }
  
  static int walkera0701_connect(struct walkera_dev *w, int parport)
  {
  	int error;
  
  	w->parport = parport_find_number(parport);
  	if (!w->parport) {
  		pr_err("parport %d does not exist\n", parport);
  		return -ENODEV;
  	}
  
  	if (w->parport->irq == -1) {
  		pr_err("parport %d does not have interrupt assigned\n",
  			parport);
  		error = -EINVAL;
  		goto err_put_parport;
  	}
  
  	w->pardevice = parport_register_device(w->parport, "walkera0701",
  				    NULL, NULL, walkera0701_irq_handler,
  				    PARPORT_DEV_EXCL, w);
  	if (!w->pardevice) {
  		pr_err("failed to register parport device\n");
  		error = -EIO;
  		goto err_put_parport;
  	}
  
  	if (parport_negotiate(w->pardevice->port, IEEE1284_MODE_COMPAT)) {
  		pr_err("failed to negotiate parport mode\n");
  		error = -EIO;
  		goto err_unregister_device;
  	}
  
  	hrtimer_init(&w->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	w->timer.function = timer_handler;
  
  	w->input_dev = input_allocate_device();
  	if (!w->input_dev) {
  		pr_err("failed to allocate input device\n");
  		error = -ENOMEM;
  		goto err_unregister_device;
  	}
  
  	input_set_drvdata(w->input_dev, w);
  	w->input_dev->name = "Walkera WK-0701 TX";
  	w->input_dev->phys = w->parport->name;
  	w->input_dev->id.bustype = BUS_PARPORT;
  
  	/* TODO what id vendor/product/version ? */
  	w->input_dev->id.vendor = 0x0001;
  	w->input_dev->id.product = 0x0001;
  	w->input_dev->id.version = 0x0100;
  	w->input_dev->dev.parent = w->parport->dev;
  	w->input_dev->open = walkera0701_open;
  	w->input_dev->close = walkera0701_close;
  
  	w->input_dev->evbit[0] = BIT(EV_ABS) | BIT_MASK(EV_KEY);
  	w->input_dev->keybit[BIT_WORD(BTN_GEAR_DOWN)] = BIT_MASK(BTN_GEAR_DOWN);
  
  	input_set_abs_params(w->input_dev, ABS_X, -512, 512, 0, 0);
  	input_set_abs_params(w->input_dev, ABS_Y, -512, 512, 0, 0);
  	input_set_abs_params(w->input_dev, ABS_Z, -512, 512, 0, 0);
  	input_set_abs_params(w->input_dev, ABS_THROTTLE, -512, 512, 0, 0);
  	input_set_abs_params(w->input_dev, ABS_RUDDER, -512, 512, 0, 0);
  	input_set_abs_params(w->input_dev, ABS_MISC, -512, 512, 0, 0);
  
  	error = input_register_device(w->input_dev);
  	if (error) {
  		pr_err("failed to register input device\n");
  		goto err_free_input_dev;
  	}
  
  	return 0;
  
  err_free_input_dev:
  	input_free_device(w->input_dev);
  err_unregister_device:
  	parport_unregister_device(w->pardevice);
  err_put_parport:
  	parport_put_port(w->parport);
  	return error;
  }
  
  static void walkera0701_disconnect(struct walkera_dev *w)
  {
  	input_unregister_device(w->input_dev);
  	parport_unregister_device(w->pardevice);
  	parport_put_port(w->parport);
  }
  
  static int __init walkera0701_init(void)
  {
  	return walkera0701_connect(&w_dev, walkera0701_pp_no);
  }
  
  static void __exit walkera0701_exit(void)
  {
  	walkera0701_disconnect(&w_dev);
  }
  
  module_init(walkera0701_init);
  module_exit(walkera0701_exit);
  