devfloppy.c

著名操作系统Plan 9的第三版的部分核心源代码。现在很难找到了。Plan 9是bell实验室开发的Unix后继者。

/*
 *  send a command to the floppy
 */
static int
floppycmd(void)
{
	int i;
	int tries;

	fl.nstat = 0;
	for(i = 0; i < fl.ncmd; i++){
		for(tries = 0; ; tries++){
			if((inb(Pmsr)&(Ffrom|Fready)) == Fready)
				break;
			if(tries > 1000){
				DPRINT("cmd %ux can't be sent (%d)\n", fl.cmd[0], i);
				fldump();

				/* empty fifo, might have been a bad command */
				floppyresult();
				return -1;
			}
			microdelay(8);	/* for machine independence */
		}
		outb(Pfdata, fl.cmd[i]);
	}
	return 0;
}

/*
 *  get a command result from the floppy
 *
 *  when the controller goes ready waiting for a command
 *  (instead of sending results), we're done
 * 
 */
static int
floppyresult(void)
{
	int i, s;
	int tries;

	/* get the result of the operation */
	for(i = 0; i < sizeof(fl.stat); i++){
		/* wait for status byte */
		for(tries = 0; ; tries++){
			s = inb(Pmsr)&(Ffrom|Fready);
			if(s == Fready){
				fl.nstat = i;
				return fl.nstat;
			}
			if(s == (Ffrom|Fready))
				break;
			if(tries > 1000){
				DPRINT("floppyresult: %d stats\n", i);
				fldump();
				fl.confused = 1;
				return -1;
			}
			microdelay(8);	/* for machine independence */
		}
		fl.stat[i] = inb(Pfdata);
	}
	fl.nstat = sizeof(fl.stat);
	return fl.nstat;
}

/*
 *  calculate physical address of a logical byte offset into the disk
 *
 *  truncate dp->length if it crosses a track boundary
 */
static void
floppypos(FDrive *dp, long off)
{
	int lsec;
	int ltrack;
	int end;

	lsec = off/dp->t->bytes;
	ltrack = lsec/dp->t->sectors;
	dp->tcyl = ltrack/dp->t->heads;
	dp->tsec = (lsec % dp->t->sectors) + 1;
	dp->thead = (lsec/dp->t->sectors) % dp->t->heads;

	/*
	 *  can't read across track boundaries.
	 *  if so, decrement the bytes to be read.
	 */
	end = (ltrack+1)*dp->t->sectors*dp->t->bytes;
	if(off+dp->len > end)
		dp->len = end - off;
}

/*
 *  get the interrupt cause from the floppy.
 */
static int
floppysense(void)
{
	fl.ncmd = 0;
	fl.cmd[fl.ncmd++] = Fsense;
	if(floppycmd() < 0)
		return -1;
	if(floppyresult() < 2){
		DPRINT("can't read sense response\n");
		fldump();
		fl.confused = 1;
		return -1;
	}
	return 0;
}

static int
cmddone(void *)
{
	return fl.ncmd == 0;
}

/*
 *  Wait for a floppy interrupt.  If none occurs in 5 seconds, we
 *  may have missed one.  This only happens on some portables which
 *  do power management behind our backs.  Call the interrupt
 *  routine to try to clear any conditions.
 */
static void
floppywait(void)
{
	tsleep(&fl.r, cmddone, 0, 5000);
	if(!cmddone(0)){
		floppyintr(0);
		fl.confused = 1;
	}
}

/*
 *  we've lost the floppy position, go to cylinder 0.
 */
static int
floppyrecal(FDrive *dp)
{
	dp->ccyl = -1;
	dp->cyl = -1;

	fl.ncmd = 0;
	fl.cmd[fl.ncmd++] = Frecal;
	fl.cmd[fl.ncmd++] = dp->dev;
	if(floppycmd() < 0)
		return -1;
	floppywait();
	if(fl.nstat < 2){
		DPRINT("recalibrate: confused %ux\n", inb(Pmsr));
		fl.confused = 1;
		return -1;
	}
	if((fl.stat[0] & (Codemask|Seekend)) != Seekend){
		DPRINT("recalibrate: failed\n");
		dp->confused = 1;
		return -1;
	}
	dp->cyl = fl.stat[1];
	if(dp->cyl != 0){
		DPRINT("recalibrate: wrong cylinder %d\n", dp->cyl);
		dp->cyl = -1;
		dp->confused = 1;
		return -1;
	}

	dp->confused = 0;
	return 0;
}

/*
 *  if the controller or a specific drive is in a confused state,
 *  reset it and get back to a known state
 */
static void
floppyrevive(void)
{
	FDrive *dp;

	/*
	 *  reset the controller if it's confused
	 */
	if(fl.confused){
		DPRINT("floppyrevive in\n");
		fldump();

		/* reset controller and turn all motors off */
		splhi();
		fl.ncmd = 1;
		fl.cmd[0] = 0;
		outb(Pdor, 0);
		delay(10);
		outb(Pdor, Fintena|Fena);
		delay(10);
		spllo();
		fl.motor = 0;
		fl.confused = 0;
		floppywait();

		/* mark all drives in an unknown state */
		for(dp = fl.d; dp < &fl.d[fl.ndrive]; dp++)
			dp->confused = 1;

		/* set rate to a known value */
		outb(Pdsr, 0);
		fl.rate = 0;

		DPRINT("floppyrevive out\n");
		fldump();
	}
}

/*
 *  seek to the target cylinder
 *
 *	interrupt, no results
 */
static long
floppyseek(FDrive *dp, long off)
{
	floppypos(dp, off);
	if(dp->cyl == dp->tcyl)
		return dp->tcyl;
	dp->cyl = -1;

	fl.ncmd = 0;
	fl.cmd[fl.ncmd++] = Fseek;
	fl.cmd[fl.ncmd++] = (dp->thead<<2) | dp->dev;
	fl.cmd[fl.ncmd++] = dp->tcyl * dp->t->steps;
	if(floppycmd() < 0)
		return -1;
	floppywait();
	if(fl.nstat < 2){
		DPRINT("seek: confused\n");
		fl.confused = 1;
		return -1;
	}
	if((fl.stat[0] & (Codemask|Seekend)) != Seekend){
		DPRINT("seek: failed\n");
		dp->confused = 1;
		return -1;
	}

	dp->cyl = dp->tcyl;
	return dp->tcyl;
}

/*
 *  read or write to floppy.  try up to three times.
 */
static long
floppyxfer(FDrive *dp, int cmd, void *a, long off, long n)
{
	long offset;
	int tries;

	if(off >= dp->t->cap)
		return 0;
	if(off + n > dp->t->cap)
		n = dp->t->cap - off;

	/* retry on error (until it gets ridiculous) */
	tries = 0;
	while(waserror()){
		if(tries++ > 20)
			nexterror();
		DPRINT("floppyxfer: retrying\n");
		/*floppyon(dp);*/
	}

	dp->len = n;
	if(floppyseek(dp, off) < 0){
		DPRINT("xfer: seek failed\n");
		dp->confused = 1;
		error(Eio);
	}

	/*
	 *  set up the dma (dp->len may be trimmed)
	 */
	if(waserror()){
		dmaend(DMAchan);
		nexterror();
	}
	dp->len = dmasetup(DMAchan, a, dp->len, cmd==Fread);
	if(dp->len < 0)
		error(Eio);

	/*
	 *  start operation
	 */
	fl.ncmd = 0;
	fl.cmd[fl.ncmd++] = cmd | (dp->t->heads > 1 ? Fmulti : 0);
	fl.cmd[fl.ncmd++] = (dp->thead<<2) | dp->dev;
	fl.cmd[fl.ncmd++] = dp->tcyl;
	fl.cmd[fl.ncmd++] = dp->thead;
	fl.cmd[fl.ncmd++] = dp->tsec;
	fl.cmd[fl.ncmd++] = dp->t->bcode;
	fl.cmd[fl.ncmd++] = dp->t->sectors;
	fl.cmd[fl.ncmd++] = dp->t->gpl;
	fl.cmd[fl.ncmd++] = 0xFF;
	if(floppycmd() < 0)
		error(Eio);

	/* Poll ready bits and transfer data */
	floppyexec((char*)a, dp->len, cmd==Fread);

	/*
	 *  give bus to DMA, floppyintr() will read result
	 */
	floppywait();
	dmaend(DMAchan);
	poperror();

	/*
	 *  check for errors
	 */
	if(fl.nstat < 7){
		DPRINT("xfer: confused\n");
		fl.confused = 1;
		error(Eio);
	}
	if((fl.stat[0] & Codemask)!=0 || fl.stat[1] || fl.stat[2]){
		DPRINT("xfer: failed %ux %ux %ux\n", fl.stat[0],
			fl.stat[1], fl.stat[2]);
		DPRINT("offset %lud len %ld\n", off, dp->len);
		if((fl.stat[0]&Codemask)==Cmdexec && fl.stat[1]==Overrun){
			DPRINT("DMA overrun: retry\n");
		} else
			dp->confused = 1;
		error(Eio);
	}

	/*
	 *  check for correct cylinder
	 */
	offset = fl.stat[3] * dp->t->heads + fl.stat[4];
	offset = offset*dp->t->sectors + fl.stat[5] - 1;
	offset = offset * c2b[fl.stat[6]];
	if(offset != off+dp->len){
		DPRINT("xfer: ends on wrong cyl\n");
		dp->confused = 1;
		error(Eio);
	}
	poperror();

	dp->lasttouched = m->ticks;
	return dp->len;
}

/*
 *  format a track
 */
static void
floppyformat(FDrive *dp, char *params)
{
 	int cyl, h, sec;
	ulong track;
	uchar *buf, *bp;
	FType *t;
	char *f[3];

	/*
	 *  set the type
	 */
	if(getfields(params, f, 3, 1, " ") > 1){
		for(t = floppytype; t < &floppytype[nelem(floppytype)]; t++){
			if(strcmp(f[1], t->name)==0 && t->dt==dp->dt){
				dp->t = t;
				floppydir[NFDIR*dp->dev].length = dp->t->cap;
				break;
			}
		}
		if(t >= &floppytype[nelem(floppytype)])
			error(Ebadarg);
	} else {
		floppysetdef(dp);
		t = dp->t;
	}

	/*
	 *  buffer for per track info
	 */
	buf = smalloc(t->sectors*4);
	if(waserror()){
		free(buf);
		nexterror();
	}

	/* force a recalibrate to cylinder 0 */
	dp->confused = 1;
	if(!waserror()){
		floppyon(dp);
		poperror();
	}

	/*
	 *  format a track at time
	 */
	for(track = 0; track < t->tracks*t->heads; track++){
		cyl = track/t->heads;
		h = track % t->heads;

		/*
		 *  seek to track, ignore errors
		 */
		floppyseek(dp, track*t->tsize);
		dp->cyl = cyl;
		dp->confused = 0;

		/*
		 *  set up the dma (dp->len may be trimmed)
		 */
		bp = buf;
		for(sec = 1; sec <= t->sectors; sec++){
			*bp++ = cyl;
			*bp++ = h;
			*bp++ = sec;
			*bp++ = t->bcode;
		}
		if(waserror()){
			dmaend(DMAchan);
			nexterror();
		}
		if(dmasetup(DMAchan, buf, bp-buf, 0) < 0)
			error(Eio);

		/*
		 *  start operation
		 */
		fl.ncmd = 0;
		fl.cmd[fl.ncmd++] = Fformat;
		fl.cmd[fl.ncmd++] = (h<<2) | dp->dev;
		fl.cmd[fl.ncmd++] = t->bcode;
		fl.cmd[fl.ncmd++] = t->sectors;
		fl.cmd[fl.ncmd++] = t->fgpl;
		fl.cmd[fl.ncmd++] = 0x5a;
		if(floppycmd() < 0)
			error(Eio);

		/* Poll ready bits and transfer data */
		floppyexec((char *)buf, bp-buf, 0);

		/*
		 *  give bus to DMA, floppyintr() will read result
		 */
		floppywait();
		dmaend(DMAchan);
		poperror();

		/*
		 *  check for errors
		 */
		if(fl.nstat < 7){
			DPRINT("format: confused\n");
			fl.confused = 1;
			error(Eio);
		}
		if((fl.stat[0]&Codemask)!=0 || fl.stat[1]|| fl.stat[2]){
			DPRINT("format: failed %ux %ux %ux\n",
				fl.stat[0], fl.stat[1], fl.stat[2]);
			dp->confused = 1;
			error(Eio);
		}
	}
	free(buf);
	dp->confused = 1;
	poperror();
}

static void
floppyintr(Ureg *)
{
	switch(fl.cmd[0]&~Fmulti){
	case Fread:
	case Fwrite:
	case Fformat:
	case Fdumpreg: 
		floppyresult();
		break;
	case Fseek:
	case Frecal:
	default:
		floppysense();	/* to clear interrupt */
		break;
	}
	fl.ncmd = 0;
	wakeup(&fl.r);
}

Dev floppydevtab = {
	'f',
	"floppy",

	floppyreset,
	devinit,
	floppyattach,
	devclone,
	floppywalk,
	floppystat,
	floppyopen,
	devcreate,
	floppyclose,
	floppyread,
	devbread,
	floppywrite,
	devbwrite,
	devremove,
	devwstat,
};