devfloppy.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>

#include	"lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"io.h"
#include	"ureg.h"

#include	"fs.h"
#include	"devfloppy.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(0)print

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 vlong	pcfloppyseek(FDrive*, vlong);
static int	floppysense(void);
static void	floppywait(int);
static long	floppyxfer(FDrive*, int, void*, long, long);

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));
}

static void
floppyalarm(Alarm* a)
{
	FDrive *dp;

	for(dp = fl.d; dp < &fl.d[fl.ndrive]; dp++){
		if((fl.motor&MOTORBIT(dp->dev)) && TK2SEC(m->ticks - dp->lasttouched) > 5)
			floppyoff(dp);
	}

	alarm(5*1000, floppyalarm, 0);
	cancel(a);
}

/*
 *  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;
			break;
		}
}

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

int
floppyinit(void)
{
	FDrive *dp;
	FType *t;
	ulong maxtsize;
	int mask;

	dmainit(DMAchan);

	floppysetup0(&fl);

	/*
	 *  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;
	}

	fl.selected = fl.d;

	floppydetach = _floppydetach;
	floppydetach();

	/*
	 *  init drives
	 */
	mask = 0;
	for(dp = fl.d; dp < &fl.d[fl.ndrive]; dp++){
		dp->dev = dp - fl.d;
		if(dp->dt == Tnone)
			continue;
		mask |= 1<<dp->dev;
		floppysetdef(dp);
		dp->cyl = -1;			/* because we don't know */
		dp->cache = (uchar*)xspanalloc(maxtsize, BY2PG, 64*1024);
		dp->ccyl = -1;
		dp->vers = 0;
		dp->maxtries = 5;
	}

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

	floppysetup1(&fl);

	/* to turn the motor off when inactive */
	alarm(5*1000, floppyalarm, 0);

	return mask;
}

void
floppyinitdev(int i, char *name)
{
	if(i >= fl.ndrive)
		panic("floppyinitdev");
	sprint(name, "fd%d", i);
}

void
floppyprintdevs(int i)
{
	if(i >= fl.ndrive)
		panic("floppyprintdevs");
	print(" fd%d", i);
}

int
floppyboot(int dev, char *file, Boot *b)
{
	Fs *fs;

	if(strncmp(file, "dos!", 4) == 0)
		file += 4;
	else if(strchr(file, '!') || strcmp(file, "")==0) {
		print("syntax is fd0!file\n");
		return -1;
	}

	fs = floppygetfspart(dev, "dos", 1);
	if(fs == nil)
		return -1;

	return fsboot(fs, file, b);
}

void
floppyprintbootdevs(int dev)
{
	print(" fd%d", dev);
}

/*
 *  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 int
changed(FDrive *dp)
{
	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);
		dp->maxtries = 3;
		start = dp->t;

		/* flopppyon fails if there's no drive */
		dp->confused = 1;	/* make floppyon recal */
		if(floppyon(dp) < 0)
			return -1;

		pcfloppyseek(dp, dp->t->heads*dp->t->tsize);

		while(floppyxfer(dp, Fread, dp->cache, 0, dp->t->tsize) <= 0){

			/*
			 *  if the xfer attempt doesn't clear the changed bit,
			 *  there's no floppy in the drive
			 */
			if(inb(Pdir)&Fchange)
				return -1;

			while(++dp->t){
				if(dp->t == &floppytype[nelem(floppytype)])
					dp->t = floppytype;
				if(dp->dt == dp->t->dt)
					break;
			}

			/* flopppyon fails if there's no drive */
			if(floppyon(dp) < 0)
				return -1;

			DPRINT("changed: trying %s\n", dp->t->name);
			fldump();
			if(dp->t == start)
				return -1;
		}
	}

	return 0;
}

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;
}

long
floppyread(Fs *fs, void *a, long n)
{
	FDrive *dp;
	long rv, offset;
	int sec, head, cyl;
	long len;
	uchar *aa;

	aa = a;
	dp = &fl.d[fs->dev];

	offset = dp->offset;
	floppyon(dp);
	if(changed(dp))
		return -1;

	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);
	}
	dp->offset = offset+rv;

	return rv;
}

void*
floppygetfspart(int i, char *name, int chatty)
{
	static Fs fs;

	if(strcmp(name, "dos") != 0){
		if(chatty)
			print("unknown partition fd%d!%s (use fd%d!dos)\n", i, name, i);
		return nil;
	}

	fs.dev = i;
	fs.diskread = floppyread;
	fs.diskseek = floppyseek;

	/* sometimes we get spurious errors and doing it again works */
	if(dosinit(&fs) < 0 && dosinit(&fs) < 0){
		if(chatty)
			print("fd%d!%s does not contain a FAT file system\n", i, name);
		return nil;
	}
	return &fs;
}

static int
return0(void*)
{
	return 0;
}

static void
timedsleep(int (*f)(void*), void* arg, int ms)
{
	int s;
	ulong end;

	end = m->ticks + 1 + MS2TK(ms);
	while(m->ticks < end && !(*f)(arg)){
		s = spllo();
		delay(10);
		splx(s);
	}
}

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

	if(fl.confused)
		floppyrevive();

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