#include	"u.h"
#include	"lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"errno.h"
#include	"devtab.h"

#include	"io.h"

typedef struct Rtc	Rtc;
typedef struct Nvram	Nvram;

/*
 * length of nvram is 2048
 * the last addresses are reserved by convention for
 * a checksum and setting the real time clock
 */
enum{
	NVLEN	= 2046,
	NVCKSUM = 2046,
	NVRTC	= 2047,
	Nbcd = 8,	/* number of bcd bytes in the clock */
	Qrtc = 1,
	Qnvram,
};

struct Nvram{
	uchar	val;
	uchar	pad[7];
};

struct Rtc
{
	int	sec;
	int	min;
	int	hour;
	int	mday;
	int	mon;
	int	year;
};

QLock	rtclock;		/* mutex on nvram operations */

static Dirtab rtcdir[]={
	"rtc",		{Qrtc, 0},	0,	0644,
	"nvram",	{Qnvram, 0},	0,	0600,
};
#define	NRTC	(sizeof(rtcdir)/sizeof(rtcdir[0]))

static uchar pattern[] =
{
	0xc5, 0x3a, 0xa3, 0x5c, 0xc5, 0x3a, 0xa3, 0x5c
};

ulong	rtc2sec(Rtc*);
void	sec2rtc(ulong, Rtc*);
int	*yrsize(int);
void	setrtc(Rtc*);
long	rtctime(void);
void	nvcksum(void);

void
rtcreset(void)
{
}

void
rtcinit(void)
{
}

Chan*
rtcattach(char *spec)
{
	return devattach('r', spec);
}

Chan*
rtcclone(Chan *c, Chan *nc)
{
	return devclone(c, nc);
}

int	 
rtcwalk(Chan *c, char *name)
{
	return devwalk(c, name, rtcdir, NRTC, devgen);
}

void	 
rtcstat(Chan *c, char *dp)
{
	devstat(c, dp, rtcdir, NRTC, devgen);
}

Chan*
rtcopen(Chan *c, int omode)
{
	return devopen(c, omode, rtcdir, NRTC, devgen);
}

void	 
rtccreate(Chan *c, char *name, int omode, ulong perm)
{
	USED(c);
	error(Eperm);
}

void	 
rtcclose(Chan *c)
{
	USED(c);
}

long	 
rtcread(Chan *c, void *buf, long n, ulong offset)
{
	Nvram *nv;
	char *p;
	ulong t, ot;
	int i;

	if(c->qid.path & CHDIR)
		return devdirread(c, buf, n, rtcdir, NRTC, devgen);

	switch(c->qid.path){
	case Qrtc:
		qlock(&rtclock);
		t = rtctime();
		do{
			ot = t;
			t = rtctime();	/* make sure there's no skew */
		}while(t != ot);
		qunlock(&rtclock);
		n = readnum(offset, buf, n, t, 12);
		return n;
	case Qnvram:
		if(offset > NVLEN)
			return 0;
		if(n > NVLEN - offset)
			n = NVLEN - offset;
		nv = (Nvram *)NVRAM;
		p = buf;
		qlock(&rtclock);
		for(i = 0; i < n; i++)
			p[i] = nv[i+offset].val;
		qunlock(&rtclock);
		return n;
	}
	error(Egreg);
}

long	 
rtcwrite(Chan *c, void *buf, long n, ulong offset)
{
	Nvram *nv;
	Rtc rtc;
	ulong secs;
	char *cp, *ep;
	int i;

	switch(c->qid.path){
	case Qrtc:
		if(offset!=0)
			error(Ebadarg);
		/*
		 *  read the time
		 */
		cp = ep = buf;
		ep += n;
		while(cp < ep){
			if(*cp>='0' && *cp<='9')
				break;
			cp++;
		}
		secs = strtoul(cp, 0, 0);
		/*
		 *  convert to bcd
		 */
		sec2rtc(secs, &rtc);
		/*
		 * write it
		 */
		qlock(&rtclock);
		setrtc(&rtc);
		qunlock(&rtclock);
		return n;
	case Qnvram:
		if(offset > NVLEN)
			return 0;
		if(n > NVLEN - offset)
			n = NVLEN - offset;
		nv = (Nvram *)NVRAM;
		qlock(&rtclock);
		for(i = 0; i < n; i++)
			nv[i+offset].val = ((char*)buf)[i];
		nvcksum();
		qunlock(&rtclock);
		return n;
	}
	error(Egreg);
}

void	 
rtcremove(Chan *c)
{
	USED(c);
	error(Eperm);
}

void	 
rtcwstat(Chan *c, char *dp)
{
	USED(c);
	error(Eperm);
}

void
nvcksum(void)
{
	Nvram *nv;
	uchar cksum;
	int i;

	/*
	 * Seed the checksum so all-zeroes (all-ones) nvram doesn't have a zero
	 * (all-ones) checksum.
	 */
	cksum = 0xa5;
	nv = (Nvram *)NVRAM;
	for(i = 0; i < NVLEN; i++){
		cksum ^= nv[i].val;
		cksum = (cksum << 1) | ((cksum >> 7) & 1);
	}
	nv[NVCKSUM].val = cksum;
}

/*
 *  issue pattern recognition bits to nv ram to address the
 *  real time clock
 */
void
rtcpattern(void)
{
	uchar *nv;
	uchar ch;
	int i, j;

	nv = &((Nvram*)NVRAM)[NVRTC].val;

	/*
	 *  read the pattern sequence pointer to reset it
	 */
	ch = *nv;
	USED(ch);

	/*
	 *  stuff the pattern recognition codes one bit at
	 *  a time into *nv.
	 */
	for(i = 0; i < Nbcd; i++){
		ch = pattern[i];
		for (j = 0; j < 8; j++){
			*nv = ch & 0x1;
			ch >>= 1;
		}
	}
}

#define GETBCD(o) ((bcdclock[o]&0xf) + 10*(bcdclock[o]>>4))

long	 
rtctime(void)
{
	int i,j;
	uchar ch;
	uchar *nv;
	uchar bcdclock[Nbcd];
	char atime[64];
	Rtc rtc;

	nv = &((Nvram*)NVRAM)[NVRTC].val;

	/*
	 *  set up the pattern for the clock
	 */
	rtcpattern();

	/*
	 *  read out the clock one bit at a time
	 */
	for(i = 0; i < Nbcd; i++){
		ch = 0;
		for (j = 0; j < 8; j++)
			ch |= ((*nv & 0x1) << j);
		bcdclock[i] = ch;
	}

	/*
	 *  see if the clock oscillator is on
	 */
	if(bcdclock[4] & 0x20)
		return 0;		/* nope, time is bogus */

	/*
	 *  convert from BCD
	 */
	rtc.sec = GETBCD(1);
	rtc.min = GETBCD(2);
	rtc.hour = GETBCD(3);
	rtc.mday = GETBCD(5);
	rtc.mon = GETBCD(6);
	rtc.year = GETBCD(7);

	/*
	 *  the world starts jan 1 1970
	 */
	if(rtc.year < 70)
		rtc.year += 2000;
	else
		rtc.year += 1900;
	return rtc2sec(&rtc);
}

#define PUTBCD(n,o) bcdclock[o] = (n % 10) | (((n / 10) % 10)<<4)

void
setrtc(Rtc *rtc)
{
	int i, j;
	uchar ch;
	uchar bcdclock[Nbcd];
	uchar *nv;

	bcdclock[0] = bcdclock[4] = 0;
	PUTBCD(rtc->sec, 1);
	PUTBCD(rtc->min, 2);
	PUTBCD(rtc->hour, 3);
	PUTBCD(rtc->mday, 5);
	PUTBCD(rtc->mon, 6);
	PUTBCD(rtc->year, 7);

	/*
	 *  set up the pattern for the clock
	 */
	rtcpattern();

	/*
	 *  write the clock one bit at a time
	 */
	nv = &((Nvram*)NVRAM)[NVRTC].val;
	for(i = 0; i < Nbcd; i++){
		ch = bcdclock[i];
		for (j = 0; j < 8; j++){
			*nv = ch & 1;
			ch >>= 1;
		}
	}
}

#define SEC2MIN 60L
#define SEC2HOUR (60L*SEC2MIN)
#define SEC2DAY (24L*SEC2HOUR)

/*
 *  days per month plus days/year
 */
static	int	dmsize[] =
{
	365, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
static	int	ldmsize[] =
{
	366, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

/*
 *  return the days/month for the given year
 */
int *
yrsize(int yr)
{
	if((yr % 4) == 0)
		return ldmsize;
	else
		return dmsize;
}

/*
 *  compute seconds since Jan 1 1970
 */
ulong
rtc2sec(Rtc *rtc)
{
	ulong secs;
	int i;
	int *d2m;

	secs = 0;

	/*
	 *  seconds per year
	 */
	for(i = 1970; i < rtc->year; i++){
		d2m = yrsize(i);
		secs += d2m[0] * SEC2DAY;
	}

	/*
	 *  seconds per month
	 */
	d2m = yrsize(rtc->year);
	for(i = 1; i < rtc->mon; i++)
		secs += d2m[i] * SEC2DAY;

	secs += (rtc->mday-1) * SEC2DAY;
	secs += rtc->hour * SEC2HOUR;
	secs += rtc->min * SEC2MIN;
	secs += rtc->sec;

	return secs;
}

/*
 *  compute rtc from seconds since Jan 1 1970
 */
void
sec2rtc(ulong secs, Rtc *rtc)
{
	int d;
	long hms, day;
	int *d2m;

	/*
	 * break initial number into days
	 */
	hms = secs % SEC2DAY;
	day = secs / SEC2DAY;
	if(hms < 0) {
		hms += SEC2DAY;
		day -= 1;
	}

	/*
	 * generate hours:minutes:seconds
	 */
	rtc->sec = hms % 60;
	d = hms / 60;
	rtc->min = d % 60;
	d /= 60;
	rtc->hour = d;

	/*
	 * year number
	 */
	if(day >= 0)
		for(d = 1970; day >= *yrsize(d); d++)
			day -= *yrsize(d);
	else
		for (d = 1970; day < 0; d--)
			day += *yrsize(d-1);
	rtc->year = d;

	/*
	 * generate month
	 */
	d2m = yrsize(rtc->year);
	for(d = 1; day >= d2m[d]; d++)
		day -= d2m[d];
	rtc->mday = day + 1;
	rtc->mon = d;

	return;
}