/*
   * PPS kernel consumer API
   *
   * Copyright (C) 2009-2010   Alexander Gordeev <lasaine@lvk.cs.msu.su>
   *
   *   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; either version 2 of the License, or
   *   (at your option) any later version.
   *
   *   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.
   *
   *   You should have received a copy of the GNU General Public License
   *   along with this program; if not, write to the Free Software
   *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/init.h>
  #include <linux/spinlock.h>
  #include <linux/pps_kernel.h>
  
  #include "kc.h"
  
  /*
   * Global variables
   */
  
  /* state variables to bind kernel consumer */
  static DEFINE_SPINLOCK(pps_kc_hardpps_lock);
  /* PPS API (RFC 2783): current source and mode for kernel consumer */
  static struct pps_device *pps_kc_hardpps_dev;	/* unique pointer to device */
  static int pps_kc_hardpps_mode;		/* mode bits for kernel consumer */
  
  /* pps_kc_bind - control PPS kernel consumer binding
   * @pps: the PPS source
   * @bind_args: kernel consumer bind parameters
   *
   * This function is used to bind or unbind PPS kernel consumer according to
   * supplied parameters. Should not be called in interrupt context.
   */
  int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
  {
  	/* Check if another consumer is already bound */
  	spin_lock_irq(&pps_kc_hardpps_lock);
  
  	if (bind_args->edge == 0)
  		if (pps_kc_hardpps_dev == pps) {
  			pps_kc_hardpps_mode = 0;
  			pps_kc_hardpps_dev = NULL;
  			spin_unlock_irq(&pps_kc_hardpps_lock);
  			dev_info(pps->dev, "unbound kernel"
  					" consumer
  ");
  		} else {
  			spin_unlock_irq(&pps_kc_hardpps_lock);
  			dev_err(pps->dev, "selected kernel consumer"
  					" is not bound
  ");
  			return -EINVAL;
  		}
  	else
  		if (pps_kc_hardpps_dev == NULL ||
  				pps_kc_hardpps_dev == pps) {
  			pps_kc_hardpps_mode = bind_args->edge;
  			pps_kc_hardpps_dev = pps;
  			spin_unlock_irq(&pps_kc_hardpps_lock);
  			dev_info(pps->dev, "bound kernel consumer: "
  				"edge=0x%x
  ", bind_args->edge);
  		} else {
  			spin_unlock_irq(&pps_kc_hardpps_lock);
  			dev_err(pps->dev, "another kernel consumer"
  					" is already bound
  ");
  			return -EINVAL;
  		}
  
  	return 0;
  }
  
  /* pps_kc_remove - unbind kernel consumer on PPS source removal
   * @pps: the PPS source
   *
   * This function is used to disable kernel consumer on PPS source removal
   * if this source was bound to PPS kernel consumer. Can be called on any
   * source safely. Should not be called in interrupt context.
   */
  void pps_kc_remove(struct pps_device *pps)
  {
  	spin_lock_irq(&pps_kc_hardpps_lock);
  	if (pps == pps_kc_hardpps_dev) {
  		pps_kc_hardpps_mode = 0;
  		pps_kc_hardpps_dev = NULL;
  		spin_unlock_irq(&pps_kc_hardpps_lock);
  		dev_info(pps->dev, "unbound kernel consumer"
  				" on device removal
  ");
  	} else
  		spin_unlock_irq(&pps_kc_hardpps_lock);
  }
  
  /* pps_kc_event - call hardpps() on PPS event
   * @pps: the PPS source
   * @ts: PPS event timestamp
   * @event: PPS event edge
   *
   * This function calls hardpps() when an event from bound PPS source occurs.
   */
  void pps_kc_event(struct pps_device *pps, struct pps_event_time *ts,
  		int event)
  {
  	unsigned long flags;
  
  	/* Pass some events to kernel consumer if activated */
  	spin_lock_irqsave(&pps_kc_hardpps_lock, flags);
  	if (pps == pps_kc_hardpps_dev && event & pps_kc_hardpps_mode)
  		hardpps(&ts->ts_real, &ts->ts_raw);
  	spin_unlock_irqrestore(&pps_kc_hardpps_lock, flags);
  }