devsd.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。

	}
	if(sdev == nil || sdgetunit(sdev, subno) == nil)
		error(Enonexist);

	c = devattach(sddevtab.dc, spec);
	c->qid = (Qid){QID(sdev->index+subno, 0, Qunitdir)|CHDIR, 0};
	c->dev = sdev->index+subno;
	return c;
}

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

static int
sdwalk(Chan* c, char* name)
{
	return devwalk(c, name, nil, 0, sdgen);
}

static void
sdstat(Chan* c, char* db)
{
	devstat(c, db, nil, 0, sdgen);
}

static Chan*
sdopen(Chan* c, int omode)
{
	SDpart *pp;
	SDunit *unit;

	c = devopen(c, omode, 0, 0, sdgen);
	switch(TYPE(c->qid)){
	default:
		break;
	case Qraw:
		unit = sdunit[UNIT(c->qid)];
		if(!canlock(&unit->rawinuse)){
			c->flag &= ~COPEN;
			error(Einuse);
		}
		unit->state = Rawcmd;
		break;
	case Qpart:
		unit = sdunit[UNIT(c->qid)];
		qlock(&unit->ctl);
		if(waserror()){
			qunlock(&unit->ctl);
			c->flag &= ~COPEN;
			nexterror();
		}
		if(unit->changed)
			error(Eio);
		pp = &unit->part[PART(c->qid)];
		pp->nopen++;
		unit->nopen++;
		qunlock(&unit->ctl);
		poperror();
		break;
	}
	return c;
}

static void
sdclose(Chan* c)
{
	SDpart *pp;
	SDunit *unit;

	if(c->qid.path & CHDIR)
		return;
	if(!(c->flag & COPEN))
		return;

	switch(TYPE(c->qid)){
	default:
		break;
	case Qraw:
		unit = sdunit[UNIT(c->qid)];
		unlock(&unit->rawinuse);
		break;
	case Qpart:
		unit = sdunit[UNIT(c->qid)];
		qlock(&unit->ctl);
		if(waserror()){
			qunlock(&unit->ctl);
			c->flag &= ~COPEN;
			nexterror();
		}
		pp = &unit->part[PART(c->qid)];
		pp->nopen--;
		unit->nopen--;
		if(unit->nopen == 0)
			unit->changed = 0;
		qunlock(&unit->ctl);
		poperror();
		break;
	}
}

static long
sdbio(Chan* c, int write, char* a, long len, vlong off)
{
	long l;
	uchar *b;
	SDpart *pp;
	SDunit *unit;
	ulong bno, max, nb, offset;

	unit = sdunit[UNIT(c->qid)];

	qlock(&unit->ctl);
	if(waserror()){
		qunlock(&unit->ctl);
		nexterror();
	}
	if(unit->changed)
		error(Eio);

	/*
	 * Check the request is within bounds.
	 * Removeable drives are locked throughout the I/O
	 * in case the media changes unexpectedly.
	 * Non-removeable drives are not locked during the I/O
	 * to allow the hardware to optimise if it can; this is
	 * a little fast and loose.
	 * It's assumed that non-removeable media parameters
	 * (sectors, secsize) can't change once the drive has
	 * been brought online.
	 */
	pp = &unit->part[PART(c->qid)];
	bno = (off/unit->secsize) + pp->start;
	nb = ((off+len+unit->secsize-1)/unit->secsize) + pp->start - bno;
	max = SDmaxio/unit->secsize;
	if(nb > max)
		nb = max;
	if(bno+nb > pp->end)
		nb = pp->end - bno;
	if(bno >= pp->end || nb == 0){
		if(write)
			error(Eio);
		qunlock(&unit->ctl);
		poperror();
		return 0;
	}
	if(!(unit->inquiry[1] & 0x80)){
		qunlock(&unit->ctl);
		poperror();
	}

	b = sdmalloc(nb*unit->secsize);
	if(b == nil)
		error(Enomem);
	if(waserror()){
		sdfree(b);
		nexterror();
	}

	offset = off%unit->secsize;
	if(write){
		if(offset || (len%unit->secsize)){
			l = unit->dev->ifc->bio(unit, 0, 0, b, nb, bno);
			if(l < 0)
				error(Eio);
			if(l < (nb*unit->secsize)){
				nb = l/unit->secsize;
				l = nb*unit->secsize - offset;
				if(len > l)
					len = l;
			}
		}
		memmove(b+offset, a, len);
		l = unit->dev->ifc->bio(unit, 0, 1, b, nb, bno);
		if(l < 0)
			error(Eio);
		if(l < offset)
			len = 0;
		else if(len > l - offset)
			len = l - offset;
	}
	else {
		l = unit->dev->ifc->bio(unit, 0, 0, b, nb, bno);
		if(l < 0)
			error(Eio);
		if(l < offset)
			len = 0;
		else if(len > l - offset)
			len = l - offset;
		memmove(a, b+offset, len);
	}
	sdfree(b);
	poperror();

	if(unit->inquiry[1] & 0x80){
		qunlock(&unit->ctl);
		poperror();
	}

	return len;
}

static long
sdrio(SDreq* r, void* a, long n)
{
	void *data;

	if(n >= SDmaxio || n < 0)
		error(Etoobig);

	data = nil;
	if(n){
		if((data = sdmalloc(n)) == nil)
			error(Enomem);
		if(r->write)
			memmove(data, a, n);
	}
	r->data = data;
	r->dlen = n;

	if(waserror()){
		if(data != nil){
			sdfree(data);
			r->data = nil;
		}
		nexterror();
	}

	if(r->unit->dev->ifc->rio(r) != SDok)
		error(Eio);

	if(!r->write && r->rlen > 0)
		memmove(a, data, r->rlen);
	if(data != nil){
		sdfree(data);
		r->data = nil;
	}
	poperror();

	return r->rlen;
}

static long
sdread(Chan *c, void *a, long n, vlong off)
{
	char *p;
	SDpart *pp;
	SDunit *unit;
	ulong offset;
	int i, l, status;

	offset = off;
	switch(TYPE(c->qid)){
	default:
		error(Eperm);
	case Qtopdir:
	case Qunitdir:
		return devdirread(c, a, n, 0, 0, sdgen);
	case Qctl:
		unit = sdunit[UNIT(c->qid)];
		p = malloc(READSTR);
		l = snprint(p, READSTR, "inquiry %.48s\n",
			(char*)unit->inquiry+8);
		qlock(&unit->ctl);
		/*
		 * If there's a device specific routine it must
		 * provide all information pertaining to night geometry
		 * and the garscadden trains.
		 */
		if(unit->dev->ifc->rctl)
			l += unit->dev->ifc->rctl(unit, p+l, READSTR-l);
		if(!unit->changed && unit->sectors){
			if(unit->dev->ifc->rctl == nil)
				l += snprint(p+l, READSTR-l,
					"geometry %ld %ld\n",
					unit->sectors, unit->secsize);
			pp = unit->part;
			for(i = 0; i < SDnpart; i++){
				if(pp->valid)
					l += snprint(p+l, READSTR-l,
						"part %.*s %lud %lud\n",
						NAMELEN, pp->name,
						pp->start, pp->end);
				pp++;
			}
		}
		qunlock(&unit->ctl);
		l = readstr(offset, a, n, p);
		free(p);
		return l;
	case Qraw:
		unit = sdunit[UNIT(c->qid)];
		if(unit->state == Rawdata){
			unit->state = Rawstatus;
			return sdrio(unit->req, a, n);
		}
		else if(unit->state == Rawstatus){
			status = unit->req->status;
			unit->state = Rawcmd;
			free(unit->req);
			unit->req = nil;
			return readnum(0, a, n, status, NUMSIZE);
		}
		break;
	case Qpart:
		return sdbio(c, 0, a, n, off);
	}

	return 0;
}

static long
sdwrite(Chan *c, void *a, long n, vlong off)
{
	Cmdbuf *cb;
	SDreq *req;
	SDunit *unit;
	ulong end, start;

	switch(TYPE(c->qid)){
	default:
		error(Eperm);
	case Qctl:
		cb = parsecmd(a, n);
		unit = sdunit[UNIT(c->qid)];

		qlock(&unit->ctl);
		if(waserror()){
			qunlock(&unit->ctl);
			free(cb);
			nexterror();
		}
		if(unit->changed)
			error(Eio);

		if(cb->nf < 1)
			error(Ebadctl);
		if(strcmp(cb->f[0], "part") == 0){
			if(cb->nf != 4 || unit->npart >= SDnpart)
				error(Ebadctl);
			if(unit->sectors == 0 && !sdinitpart(unit))
				error(Eio);
			start = strtoul(cb->f[2], 0, 0);
			end = strtoul(cb->f[3], 0, 0);
			sdaddpart(unit, cb->f[1], start, end);
		}
		else if(strcmp(cb->f[0], "delpart") == 0){
			if(cb->nf != 2 || unit->part == nil)
				error(Ebadctl);
			sddelpart(unit, cb->f[1]);
		}
		else if(unit->dev->ifc->wctl)
			unit->dev->ifc->wctl(unit, cb);
		else
			error(Ebadctl);
		qunlock(&unit->ctl);
		poperror();
		free(cb);
		break;

	case Qraw:
		unit = sdunit[UNIT(c->qid)];
		switch(unit->state){
		case Rawcmd:
			if(n < 6 || n > sizeof(req->cmd))
				error(Ebadarg);
			if((req = malloc(sizeof(SDreq))) == nil)
				error(Enomem);
			req->unit = unit;
			memmove(req->cmd, a, n);
			req->clen = n;
			req->flags = SDnosense;
			req->status = ~0;

			unit->req = req;
			unit->state = Rawdata;
			break;

		case Rawstatus:
			unit->state = Rawcmd;
			free(unit->req);
			unit->req = nil;
			error(Ebadusefd);

		case Rawdata:
			if(unit->state != Rawdata)
				error(Ebadusefd);
			unit->state = Rawstatus;

			unit->req->write = 1;
			return sdrio(unit->req, a, n);
		}
		break;
	case Qpart:
		return sdbio(c, 1, a, n, off);
	}

	return n;
}

static void
sdwstat(Chan* c, char* dp)
{
	Dir d;
	SDpart *pp;
	SDunit *unit;

	if((c->qid.path & CHDIR) || TYPE(c->qid) != Qpart)
		error(Eperm);

	unit = sdunit[UNIT(c->qid)];
	qlock(&unit->ctl);
	if(waserror()){
		qunlock(&unit->ctl);
		nexterror();
	}

	if(unit->changed)
		error(Enonexist);
	pp = &unit->part[PART(c->qid)];
	if(!pp->valid)
		error(Enonexist);
	if(strncmp(up->user, pp->user, NAMELEN) && !iseve())
		error(Eperm);

	convM2D(dp, &d);
	strncpy(pp->user, d.uid, NAMELEN);
	pp->perm = d.mode&0777;

	qunlock(&unit->ctl);
	poperror();
}

Dev sddevtab = {
	'S',
	"sd",

	sdreset,
	devinit,
	sdattach,
	sdclone,
	sdwalk,
	sdstat,
	sdopen,
	devcreate,
	sdclose,
	sdread,
	devbread,
	sdwrite,
	devbwrite,
	devremove,
	sdwstat,
};