/* ir-xmp-decoder.c - handle XMP IR Pulse/Space protocol
   *
   * Copyright (C) 2014 by Marcel Mol
   *
   * This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation version 2 of the License.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   * - Based on info from http://www.hifi-remote.com
   * - Ignore Toggle=9 frames
   * - Ignore XMP-1 XMP-2 difference, always store 16 bit OBC
   */
  
  #include <linux/bitrev.h>
  #include <linux/module.h>
  #include "rc-core-priv.h"
  
  #define XMP_UNIT		  136000 /* ns */
  #define XMP_LEADER		  210000 /* ns */
  #define XMP_NIBBLE_PREFIX	  760000 /* ns */
  #define	XMP_HALFFRAME_SPACE	13800000 /* ns */
  #define	XMP_TRAILER_SPACE	20000000 /* should be 80ms but not all dureation supliers can go that high */
  
  enum xmp_state {
  	STATE_INACTIVE,
  	STATE_LEADER_PULSE,
  	STATE_NIBBLE_SPACE,
  };
  
  /**
   * ir_xmp_decode() - Decode one XMP pulse or space
   * @dev:	the struct rc_dev descriptor of the device
   * @duration:	the struct ir_raw_event descriptor of the pulse/space
   *
   * This function returns -EINVAL if the pulse violates the state machine
   */
  static int ir_xmp_decode(struct rc_dev *dev, struct ir_raw_event ev)
  {
  	struct xmp_dec *data = &dev->raw->xmp;
  
  	if (!(dev->enabled_protocols & RC_BIT_XMP))
  		return 0;
  
  	if (!is_timing_event(ev)) {
  		if (ev.reset)
  			data->state = STATE_INACTIVE;
  		return 0;
  	}
  
  	IR_dprintk(2, "XMP decode started at state %d %d (%uus %s)
  ",
  		   data->state, data->count, TO_US(ev.duration), TO_STR(ev.pulse));
  
  	switch (data->state) {
  
  	case STATE_INACTIVE:
  		if (!ev.pulse)
  			break;
  
  		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) {
  			data->count = 0;
  			data->state = STATE_NIBBLE_SPACE;
  		}
  
  		return 0;
  
  	case STATE_LEADER_PULSE:
  		if (!ev.pulse)
  			break;
  
  		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2))
  			data->state = STATE_NIBBLE_SPACE;
  
  		return 0;
  
  	case STATE_NIBBLE_SPACE:
  		if (ev.pulse)
  			break;
  
  		if (geq_margin(ev.duration, XMP_TRAILER_SPACE, XMP_NIBBLE_PREFIX)) {
  			int divider, i;
  			u8 addr, subaddr, subaddr2, toggle, oem, obc1, obc2, sum1, sum2;
  			u32 *n;
  			u32 scancode;
  
  			if (data->count != 16) {
  				IR_dprintk(2, "received TRAILER period at index %d: %u
  ",
  					data->count, ev.duration);
  				data->state = STATE_INACTIVE;
  				return -EINVAL;
  			}
  
  			n = data->durations;
  			/*
  			 * the 4th nibble should be 15 so base the divider on this
  			 * to transform durations into nibbles. Substract 2000 from
  			 * the divider to compensate for fluctuations in the signal
  			 */
  			divider = (n[3] - XMP_NIBBLE_PREFIX) / 15 - 2000;
  			if (divider < 50) {
  				IR_dprintk(2, "divider to small %d.
  ", divider);
  				data->state = STATE_INACTIVE;
  				return -EINVAL;
  			}
  
  			/* convert to nibbles and do some sanity checks */
  			for (i = 0; i < 16; i++)
  				n[i] = (n[i] - XMP_NIBBLE_PREFIX) / divider;
  			sum1 = (15 + n[0] + n[1] + n[2] + n[3] +
  				n[4] + n[5] + n[6] + n[7]) % 16;
  			sum2 = (15 + n[8] + n[9] + n[10] + n[11] +
  				n[12] + n[13] + n[14] + n[15]) % 16;
  
  			if (sum1 != 15 || sum2 != 15) {
  				IR_dprintk(2, "checksum errors sum1=0x%X sum2=0x%X
  ",
  					sum1, sum2);
  				data->state = STATE_INACTIVE;
  				return -EINVAL;
  			}
  
  			subaddr  = n[0] << 4 | n[2];
  			subaddr2 = n[8] << 4 | n[11];
  			oem      = n[4] << 4 | n[5];
  			addr     = n[6] << 4 | n[7];
  			toggle   = n[10];
  			obc1 = n[12] << 4 | n[13];
  			obc2 = n[14] << 4 | n[15];
  			if (subaddr != subaddr2) {
  				IR_dprintk(2, "subaddress nibbles mismatch 0x%02X != 0x%02X
  ",
  					subaddr, subaddr2);
  				data->state = STATE_INACTIVE;
  				return -EINVAL;
  			}
  			if (oem != 0x44)
  				IR_dprintk(1, "Warning: OEM nibbles 0x%02X. Expected 0x44
  ",
  					oem);
  
  			scancode = addr << 24 | subaddr << 16 |
  				   obc1 << 8 | obc2;
  			IR_dprintk(1, "XMP scancode 0x%06x
  ", scancode);
  
  			if (toggle == 0) {
  				rc_keydown(dev, RC_TYPE_XMP, scancode, 0);
  			} else {
  				rc_repeat(dev);
  				IR_dprintk(1, "Repeat last key
  ");
  			}
  			data->state = STATE_INACTIVE;
  
  			return 0;
  
  		} else if (geq_margin(ev.duration, XMP_HALFFRAME_SPACE, XMP_NIBBLE_PREFIX)) {
  			/* Expect 8 or 16 nibble pulses. 16 in case of 'final' frame */
  			if (data->count == 16) {
  				IR_dprintk(2, "received half frame pulse at index %d. Probably a final frame key-up event: %u
  ",
  					data->count, ev.duration);
  				/*
  				 * TODO: for now go back to half frame position
  				 *	 so trailer can be found and key press
  				 *	 can be handled.
  				 */
  				data->count = 8;
  			}
  
  			else if (data->count != 8)
  				IR_dprintk(2, "received half frame pulse at index %d: %u
  ",
  					data->count, ev.duration);
  			data->state = STATE_LEADER_PULSE;
  
  			return 0;
  
  		} else if (geq_margin(ev.duration, XMP_NIBBLE_PREFIX, XMP_UNIT)) {
  			/* store nibble raw data, decode after trailer */
  			if (data->count == 16) {
  				IR_dprintk(2, "to many pulses (%d) ignoring: %u
  ",
  					data->count, ev.duration);
  				data->state = STATE_INACTIVE;
  				return -EINVAL;
  			}
  			data->durations[data->count] = ev.duration;
  			data->count++;
  			data->state = STATE_LEADER_PULSE;
  
  			return 0;
  
  		}
  
  		break;
  	}
  
  	IR_dprintk(1, "XMP decode failed at count %d state %d (%uus %s)
  ",
  		   data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  	data->state = STATE_INACTIVE;
  	return -EINVAL;
  }
  
  static struct ir_raw_handler xmp_handler = {
  	.protocols	= RC_BIT_XMP,
  	.decode		= ir_xmp_decode,
  };
  
  static int __init ir_xmp_decode_init(void)
  {
  	ir_raw_handler_register(&xmp_handler);
  
  	printk(KERN_INFO "IR XMP protocol handler initialized
  ");
  	return 0;
  }
  
  static void __exit ir_xmp_decode_exit(void)
  {
  	ir_raw_handler_unregister(&xmp_handler);
  }
  
  module_init(ir_xmp_decode_init);
  module_exit(ir_xmp_decode_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Marcel Mol <marcel@mesa.nl>");
  MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)");
  MODULE_DESCRIPTION("XMP IR protocol decoder");