/*
    lib/comedi.c
    comedi library routines

    COMEDI - Linux Control and Measurement Device Interface
    Copyright (C) 1997-8 David A. Schleef <ds@stm.lbl.gov>

    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.

*/

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <comedi.h>
#include <string.h>

#include <libinternal.h>



/* dt282x timer */

static int dt282x_timer(double freq,unsigned int *trigvar,double *actual_freq)
{
	int divider,prescaler;
	double basefreq=4e6;
	
	divider=floor(4e6/(freq));
	prescaler=0;
	while(divider>255){
		prescaler++;
		divider>>=1;
		basefreq/=2;
	}
	if(prescaler==1){
		prescaler++;
		divider>>=1;
		basefreq/=2;
	}
	if(prescaler>=16)return -1;
	*trigvar=(prescaler<<8)|(255-divider);
	*actual_freq=basefreq/divider;
	
	return 0;
}


/* dt2814 timer */
static int dt2814_timer(double freq,unsigned int *trigvar,double *actual_freq)
{
	double f;
	int  i;
	
	f=1e5;
	for(i=0;i<8;i++){
		if(f-freq<freq-f/10){
			*trigvar=i;
			*actual_freq=f;
			return 0;
		}
		f/=10;
	}
	*trigvar=i;
	*actual_freq=f;
	
	return 0;
}

/* atmio/pcimio timer */
static int atmio_timer(double freq,unsigned int *trigvar,double *actual_freq)
{
	unsigned int divider;
	
	divider=floor(20e6/(freq));
	*actual_freq=20e6/divider;
	*trigvar=divider-1;
	
	return 0;
}

/* acl8112 timer */
static int acl8112_timer(double freq,unsigned int *trigvar,double *actual_freq)
{
	int divider,prescaler;
	double basefreq=2e6;

	/* XXX my notes say that the prescaler and divider cannot
	   be 1.  This needs to be checked.  --ds */
	
	/* Force at least one division to get something in CTR2. */
	prescaler=1;
	divider = basefreq/(freq);

	while(divider>32767){
		prescaler*=2;
		divider>>=1;
	}

	*trigvar = (prescaler<<16) | divider;
	*actual_freq=basefreq/(divider*prescaler);
	
	return 0;
}

/* nanosec timer */
static int nanosec_timer(double freq,unsigned int *trigvar,double *actual_freq)
{
	*trigvar=(1e9/freq);
	*actual_freq=1e9/(*trigvar);

	return 0;
}

typedef int (*timerfunc)(double freq,unsigned int *trigvar,double *actual_freq);

static timerfunc timer_functions[]={
	NULL,
	dt282x_timer,
	dt2814_timer,
	atmio_timer,
	acl8112_timer,
	nanosec_timer,
};
#define N_TIMERTYPES 6

int comedi_get_timer(comedi_t *it,unsigned int subdev,double freq,
	unsigned int *trigvar,double *actual_freq)
{
	int timer_type;
	
	if(!it || !trigvar || !actual_freq)
		return -1;

	timer_type=it->subdevices[subdev].timer_type;
	
	if(timer_type==0 || timer_type>=N_TIMERTYPES)
		return -1;
	
	return (timer_functions[timer_type])(freq,trigvar,actual_freq);
}