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。

#include	"u.h"
#include	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"io.h"
#include	"../port/error.h"

#include	"floppy.h"

/* Intel 82077A (8272A compatible) floppy controller */

/* This module expects the following functions to be defined
 * elsewhere: 
 * 
 * inb()
 * outb()
 * floppyexec()
 * floppyeject() 
 * floppysetup0()
 * floppysetup1()
 * dmainit()
 * dmasetup()
 * dmaend()
 * 
 * On DMA systems, floppyexec() should be an empty function; 
 * on non-DMA systems, dmaend() should be an empty function; 
 * dmasetup() may enforce maximum transfer sizes. 
 */

enum {
	/* file types */
	Qdir=		0, 
	Qdata=		(1<<2),
	Qctl=		(2<<2),
	Qmask=		(3<<2),

	DMAchan=	2,	/* floppy dma channel */
};

#define DPRINT if(floppydebug)print
int floppydebug = 0;

/*
 *  types of drive (from PC equipment byte)
 */
enum
{
	Tnone=		0,
	T360kb=		1,
	T1200kb=	2,
	T720kb=		3,
	T1440kb=	4,
};

FType floppytype[] =
{
 { "3½HD",	T1440kb, 512, 18, 2, 1, 80, 0x1B, 0x54,	0, },
 { "3½DD",	T1440kb, 512,  9, 2, 1, 80, 0x1B, 0x54, 2, },
 { "3½DD",	T720kb,  512,  9, 2, 1, 80, 0x1B, 0x54, 2, },
 { "5¼HD",	T1200kb, 512, 15, 2, 1, 80, 0x2A, 0x50, 0, },
 { "5¼DD",	T1200kb, 512,  9, 2, 2, 40, 0x2A, 0x50, 1, },
 { "ATT3B1",	T1200kb, 512,  8, 2, 2, 48, 0x2A, 0x50, 1, },
 { "5¼DD",	T360kb,  512,  9, 2, 1, 40, 0x2A, 0x50, 2, },
};

/*
 *  bytes per sector encoding for the controller.
 *  - index for b2c is is (bytes per sector/128).
 *  - index for c2b is code from b2c
 */
static int b2c[] =
{
[1]	0,
[2]	1,
[4]	2,
[8]	3,
};
static int c2b[] =
{
	128,
	256,
	512,
	1024,
};

FController	fl;

#define MOTORBIT(i)	(1<<((i)+4))

/*
 *  predeclared
 */
static int	cmddone(void*);
static void	floppyformat(FDrive*, char*);
static void	floppykproc(void*);
static void	floppypos(FDrive*,long);
static int	floppyrecal(FDrive*);
static int	floppyresult(void);
static void	floppyrevive(void);
static long	floppyseek(FDrive*, long);
static int	floppysense(void);
static void	floppywait(void);
static long	floppyxfer(FDrive*, int, void*, long, long);

Dirtab floppydir[]={
	"fd0disk",		{Qdata + 0},	0,	0660,
	"fd0ctl",		{Qctl + 0},	0,	0660,
	"fd1disk",		{Qdata + 1},	0,	0660,
	"fd1ctl",		{Qctl + 1},	0,	0660,
	"fd2disk",		{Qdata + 2},	0,	0660,
	"fd2ctl",		{Qctl + 2},	0,	0660,
	"fd3disk",		{Qdata + 3},	0,	0660,
	"fd3ctl",		{Qctl + 3},	0,	0660,
};
#define NFDIR	2	/* directory entries/drive */

static void
fldump(void)
{
	DPRINT("sra %ux srb %ux dor %ux msr %ux dir %ux\n", inb(Psra), inb(Psrb),
		inb(Pdor), inb(Pmsr), inb(Pdir));
}

/*
 *  set floppy drive to its default type
 */
static void
floppysetdef(FDrive *dp)
{
	FType *t;

	for(t = floppytype; t < &floppytype[nelem(floppytype)]; t++)
		if(dp->dt == t->dt){
			dp->t = t;
			floppydir[NFDIR*dp->dev].length = dp->t->cap;
			break;
		}
}

static void
floppyreset(void)
{
	FDrive *dp;
	FType *t;
	ulong maxtsize;
	
	floppysetup0(&fl);
	if(fl.ndrive == 0)
		return;

	/*
	 *  init dependent parameters
	 */
	maxtsize = 0;
	for(t = floppytype; t < &floppytype[nelem(floppytype)]; t++){
		t->cap = t->bytes * t->heads * t->sectors * t->tracks;
		t->bcode = b2c[t->bytes/128];
		t->tsize = t->bytes * t->sectors;
		if(maxtsize < t->tsize)
			maxtsize = t->tsize;
	}

	dmainit(DMAchan, maxtsize);

	/*
	 *  allocate the drive storage
	 */
	fl.d = xalloc(fl.ndrive*sizeof(FDrive));
	fl.selected = fl.d;

	/*
	 *  stop the motors
	 */
	fl.motor = 0;
	delay(10);
	outb(Pdor, fl.motor | Fintena | Fena);
	delay(10);

	/*
	 *  init drives
	 */
	for(dp = fl.d; dp < &fl.d[fl.ndrive]; dp++){
		dp->dev = dp - fl.d;
		dp->dt = T1440kb;
		floppysetdef(dp);
		dp->cyl = -1;			/* because we don't know */
		dp->cache = (uchar*)xspanalloc(maxtsize, BY2PG, 64*1024);
		dp->ccyl = -1;
		dp->vers = 0;
	}

	/*
	 *  first operation will recalibrate
	 */
	fl.confused = 1;

	floppysetup1(&fl);
}

static Chan*
floppyattach(char *spec)
{
	static int kstarted;

	if(fl.ndrive == 0)
		error(Enodev);

	if(kstarted == 0){
		/*
		 *  watchdog to turn off the motors
		 */
		kstarted = 1;
		kproc("floppy", floppykproc, 0);
	}
	return devattach('f', spec);
}

static int
floppywalk(Chan *c, char *name)
{
	return devwalk(c, name, floppydir, fl.ndrive*NFDIR, devgen);
}

static void
floppystat(Chan *c, char *dp)
{
	devstat(c, dp, floppydir, fl.ndrive*NFDIR, devgen);
}

static Chan*
floppyopen(Chan *c, int omode)
{
	return devopen(c, omode, floppydir, fl.ndrive*NFDIR, devgen);
}

static void
floppyclose(Chan *)
{
}

static void
islegal(ulong offset, long n, FDrive *dp)
{
	if(offset % dp->t->bytes)
		error(Ebadarg);
	if(n % dp->t->bytes)
		error(Ebadarg);
}

/*
 *  check if the floppy has been replaced under foot.  cause
 *  an error if it has.
 *
 *  a seek and a read clears the condition.  this was determined
 *  experimentally, there has to be a better way.
 *
 *  if the read fails, cycle through the possible floppy
 *  density till one works or we've cycled through all
 *  possibilities for this drive.
 */
static void
changed(Chan *c, FDrive *dp)
{
	ulong old;
	FType *start;

	/*
	 *  if floppy has changed or first time through
	 */
	if((inb(Pdir)&Fchange) || dp->vers == 0){
		DPRINT("changed\n");
		fldump();
		dp->vers++;
		floppysetdef(dp);
		start = dp->t;
		dp->confused = 1;	/* make floppyon recal */
		floppyon(dp);
		floppyseek(dp, dp->t->heads*dp->t->tsize);
		while(waserror()){
			while(++dp->t){
				if(dp->t == &floppytype[nelem(floppytype)])
					dp->t = floppytype;
				if(dp->dt == dp->t->dt)
					break;
			}
			floppydir[NFDIR*dp->dev].length = dp->t->cap;
			floppyon(dp);
			DPRINT("changed: trying %s\n", dp->t->name);
			fldump();
			if(dp->t == start)
				nexterror();
		}
		floppyxfer(dp, Fread, dp->cache, 0, dp->t->tsize);
		poperror();
	}

	old = c->qid.vers;
	c->qid.vers = dp->vers;
	if(old && old != dp->vers)
		error(Eio);
}

static int
readtrack(FDrive *dp, int cyl, int head)
{
	int i, nn, sofar;
	ulong pos;

	nn = dp->t->tsize;
	if(dp->ccyl==cyl && dp->chead==head)
		return nn;
	pos = (cyl*dp->t->heads+head) * nn;
	for(sofar = 0; sofar < nn; sofar += i){
		dp->ccyl = -1;
		i = floppyxfer(dp, Fread, dp->cache + sofar, pos + sofar, nn - sofar);
		if(i <= 0)
			return -1;
	}
	dp->ccyl = cyl;
	dp->chead = head;
	return nn;
}

static long
floppyread(Chan *c, void *a, long n, vlong off)
{
	FDrive *dp;
	long rv;
	int sec, head, cyl;
	long len;
	uchar *aa;
	ulong offset = off;

	if(c->qid.path == CHDIR)
		return devdirread(c, a, n, floppydir, fl.ndrive*NFDIR, devgen);

	rv = 0;
	dp = &fl.d[c->qid.path & ~Qmask];
	switch ((int)(c->qid.path & Qmask)) {
	case Qdata:
		islegal(offset, n, dp);
		aa = a;

		qlock(&fl);
		if(waserror()){
			qunlock(&fl);
			nexterror();
		}
		floppyon(dp);
		changed(c, dp);
		for(rv = 0; rv < n; rv += len){
			/*
			 *  all xfers come out of the track cache
			 */
			dp->len = n - rv;
			floppypos(dp, offset+rv);
			cyl = dp->tcyl;
			head = dp->thead;
			len = dp->len;
			sec = dp->tsec;
			if(readtrack(dp, cyl, head) < 0)
				break;
			memmove(aa+rv, dp->cache + (sec-1)*dp->t->bytes, len);
		}
		qunlock(&fl);
		poperror();

		break;
	case Qctl:
		return readstr(offset, a, n, dp->t->name);
	default:
		panic("floppyread: bad qid");
	}

	return rv;
}

#define SNCMP(a, b) strncmp(a, b, sizeof(b)-1)
static long
floppywrite(Chan *c, void *a, long n, vlong off)
{
	FDrive *dp;
	long rv, i;
	char *aa = a;
	char ctlmsg[64];
	ulong offset = off;

	rv = 0;
	dp = &fl.d[c->qid.path & ~Qmask];
	switch ((int)(c->qid.path & Qmask)) {
	case Qdata:
		islegal(offset, n, dp);
		qlock(&fl);
		if(waserror()){
			qunlock(&fl);
			nexterror();
		}
		floppyon(dp);
		changed(c, dp);
		for(rv = 0; rv < n; rv += i){
			floppypos(dp, offset+rv);
			if(dp->tcyl == dp->ccyl)
				dp->ccyl = -1;
			i = floppyxfer(dp, Fwrite, aa+rv, offset+rv, n-rv);
			if(i < 0)
				break;
			if(i == 0)
				error(Eio);
		}
		qunlock(&fl);
		poperror();
		break;
	case Qctl:
		rv = n;
		qlock(&fl);
		if(waserror()){
			qunlock(&fl);
			nexterror();
		}
		if(n >= sizeof(ctlmsg))
			n = sizeof(ctlmsg) - 1;
		memmove(ctlmsg, aa, n);
		ctlmsg[n] = 0;
		if(SNCMP(ctlmsg, "eject") == 0){
			floppyeject(dp);
		} else if(SNCMP(ctlmsg, "reset") == 0){
			fl.confused = 1;
			floppyon(dp);
		} else if(SNCMP(ctlmsg, "format") == 0){
			floppyformat(dp, ctlmsg);
		} else if(SNCMP(ctlmsg, "debug") == 0){
			floppydebug = 1;
		} else
			error(Ebadctl);
		poperror();
		qunlock(&fl);
		break;
	default:
		panic("floppywrite: bad qid");
	}

	return rv;
}

static void
floppykproc(void *)
{
	FDrive *dp;

	while(waserror())
		;
	for(;;){
		for(dp = fl.d; dp < &fl.d[fl.ndrive]; dp++){
			if((fl.motor&MOTORBIT(dp->dev))
			&& TK2SEC(m->ticks - dp->lasttouched) > 5
			&& canqlock(&fl)){
				if(TK2SEC(m->ticks - dp->lasttouched) > 5)
					floppyoff(dp);
				qunlock(&fl);
			}
		}
		tsleep(&fl.kr, return0, 0, 1000);
	}
}

/*
 *  start a floppy drive's motor.
 */
static void
floppyon(FDrive *dp)
{
	int alreadyon;
	int tries;

	if(fl.confused)
		floppyrevive();

	/* start motor and select drive */
	alreadyon = fl.motor & MOTORBIT(dp->dev);
	fl.motor |= MOTORBIT(dp->dev);
	outb(Pdor, fl.motor | Fintena | Fena | dp->dev);
	if(!alreadyon){
		/* wait for drive to spin up */
		tsleep(&dp->r, return0, 0, 750);

		/* clear any pending interrupts */
		floppysense();
	}

	/* set transfer rate */
	if(fl.rate != dp->t->rate){
		fl.rate = dp->t->rate;
		outb(Pdsr, fl.rate);
	}

	/* get drive to a known cylinder */
	if(dp->confused)
		for(tries = 0; tries < 4; tries++)
			if(floppyrecal(dp) >= 0)
				break;
	dp->lasttouched = m->ticks;
	fl.selected = dp;
}

/*
 *  stop the floppy if it hasn't been used in 5 seconds
 */
static void
floppyoff(FDrive *dp)
{
	fl.motor &= ~MOTORBIT(dp->dev);
	outb(Pdor, fl.motor | Fintena | Fena | dp->dev);
}