xref: /plan9/sys/src/cmd/usb/disk/disk.c (revision 2806980e56d897a3d58ae5b586c9f594d1ff578a)
1 /*
2  * usb/disk - usb mass storage file server
3  *
4  * supports only the scsi command interface, not ata.
5  */
6 
7 #include <u.h>
8 #include <libc.h>
9 #include <ctype.h>
10 #include <fcall.h>
11 #include <thread.h>
12 #include "scsireq.h"
13 #include "usb.h"
14 #include "usbfs.h"
15 #include "ums.h"
16 
17 enum
18 {
19 	Qdir = 0,
20 	Qctl,
21 	Qraw,
22 	Qdata,
23 	Qmax,
24 };
25 
26 typedef struct Dirtab Dirtab;
27 struct Dirtab
28 {
29 	char	*name;
30 	int	mode;
31 };
32 
33 static Dirtab dirtab[] =
34 {
35 	[Qdir]	"/",	DMDIR|0555,
36 	[Qctl]	"ctl",	0664,		/* nothing secret here */
37 	[Qraw]	"raw",	0640,
38 	[Qdata]	"data",	0640,
39 };
40 
41 /*
42  * These are used by scuzz scsireq
43  */
44 int exabyte, force6bytecmds;
45 
46 int diskdebug;
47 
48 static void
49 ding(void *, char *msg)
50 {
51 	if(strstr(msg, "alarm") != nil)
52 		noted(NCONT);
53 	noted(NDFLT);
54 }
55 
56 static int
57 getmaxlun(Dev *dev)
58 {
59 	uchar max;
60 	int r;
61 
62 	max = 0;
63 	r = Rd2h|Rclass|Riface;
64 	if(usbcmd(dev, r, Getmaxlun, 0, 0, &max, 1) < 0){
65 		dprint(2, "disk: %s: getmaxlun failed: %r\n", dev->dir);
66 	}else{
67 		max &= 017;			/* 15 is the max. allowed */
68 		dprint(2, "disk: %s: maxlun %d\n", dev->dir, max);
69 	}
70 	return max;
71 }
72 
73 static int
74 umsreset(Ums *ums)
75 {
76 	int r;
77 
78 	r = Rh2d|Rclass|Riface;
79 	if(usbcmd(ums->dev, r, Umsreset, 0, 0, nil, 0) < 0){
80 		fprint(2, "disk: reset: %r\n");
81 		return -1;
82 	}
83 	return 0;
84 }
85 
86 static int
87 umsrecover(Ums *ums)
88 {
89 	if(umsreset(ums) < 0)
90 		return -1;
91 	if(unstall(ums->dev, ums->epin, Ein) < 0)
92 		dprint(2, "disk: unstall epin: %r\n");
93 
94 	/* do we need this when epin == epout? */
95 	if(unstall(ums->dev, ums->epout, Eout) < 0)
96 		dprint(2, "disk: unstall epout: %r\n");
97 	return 0;
98 }
99 
100 static void
101 umsfatal(Ums *ums)
102 {
103 	int i;
104 
105 	devctl(ums->dev, "detach");
106 	for(i = 0; i < ums->maxlun; i++)
107 		usbfsdel(&ums->lun[i].fs);
108 }
109 
110 static int
111 ispow2(uvlong ul)
112 {
113 	return (ul & (ul - 1)) == 0;
114 }
115 
116 /*
117  * return smallest power of 2 >= n
118  */
119 static int
120 log2(int n)
121 {
122 	int i;
123 
124 	for(i = 0; (1 << i) < n; i++)
125 		;
126 	return i;
127 }
128 
129 static int
130 umscapacity(Umsc *lun)
131 {
132 	uchar data[32];
133 
134 	lun->blocks = 0;
135 	lun->capacity = 0;
136 	lun->lbsize = 0;
137 	memset(data, 0, sizeof data);
138 	if(SRrcapacity(lun, data) < 0 && SRrcapacity(lun, data)  < 0)
139 		return -1;
140 	lun->blocks = GETBELONG(data);
141 	lun->lbsize = GETBELONG(data+4);
142 	if(lun->blocks == 0xFFFFFFFF){
143 		if(SRrcapacity16(lun, data) < 0){
144 			lun->lbsize = 0;
145 			lun->blocks = 0;
146 			return -1;
147 		}else{
148 			lun->lbsize = GETBELONG(data + 8);
149 			lun->blocks = (uvlong)GETBELONG(data)<<32 |
150 				GETBELONG(data + 4);
151 		}
152 	}
153 	lun->blocks++; /* SRcapacity returns LBA of last block */
154 	lun->capacity = (vlong)lun->blocks * lun->lbsize;
155 	if(diskdebug)
156 		fprint(2, "disk: logical block size %lud, # blocks %llud\n",
157 			lun->lbsize, lun->blocks);
158 	return 0;
159 }
160 
161 static int
162 umsinit(Ums *ums)
163 {
164 	uchar i;
165 	Umsc *lun;
166 	int some;
167 
168 	umsreset(ums);
169 	ums->maxlun = getmaxlun(ums->dev);
170 	ums->lun = mallocz((ums->maxlun+1) * sizeof(*ums->lun), 1);
171 	some = 0;
172 	for(i = 0; i <= ums->maxlun; i++){
173 		lun = &ums->lun[i];
174 		lun->ums = ums;
175 		lun->umsc = lun;
176 		lun->lun = i;
177 		lun->flags = Fopen | Fusb | Frw10;
178 		if(SRinquiry(lun) < 0 && SRinquiry(lun) < 0){
179 			dprint(2, "disk: lun %d inquiry failed\n", i);
180 			continue;
181 		}
182 		switch(lun->inquiry[0]){
183 		case Devdir:
184 		case Devworm:		/* a little different than the others */
185 		case Devcd:
186 		case Devmo:
187 			break;
188 		default:
189 			fprint(2, "disk: lun %d is not a disk (type %#02x)\n",
190 				i, lun->inquiry[0]);
191 			continue;
192 		}
193 		SRstart(lun, 1);
194 		/*
195 		 * we ignore the device type reported by inquiry.
196 		 * Some devices return a wrong value but would still work.
197 		 */
198 		some++;
199 		lun->inq = smprint("%.48s", (char *)lun->inquiry+8);
200 		umscapacity(lun);
201 	}
202 	if(some == 0){
203 		dprint(2, "disk: all luns failed\n");
204 		devctl(ums->dev, "detach");
205 		return -1;
206 	}
207 	return 0;
208 }
209 
210 
211 /*
212  * called by SR*() commands provided by scuzz's scsireq
213  */
214 long
215 umsrequest(Umsc *umsc, ScsiPtr *cmd, ScsiPtr *data, int *status)
216 {
217 	Cbw cbw;
218 	Csw csw;
219 	int n, nio, left;
220 	Ums *ums;
221 
222 	ums = umsc->ums;
223 
224 	memcpy(cbw.signature, "USBC", 4);
225 	cbw.tag = ++ums->seq;
226 	cbw.datalen = data->count;
227 	cbw.flags = data->write? CbwDataOut: CbwDataIn;
228 	cbw.lun = umsc->lun;
229 	if(cmd->count < 1 || cmd->count > 16)
230 		fprint(2, "disk: umsrequest: bad cmd count: %ld\n", cmd->count);
231 
232 	cbw.len = cmd->count;
233 	assert(cmd->count <= sizeof(cbw.command));
234 	memcpy(cbw.command, cmd->p, cmd->count);
235 	memset(cbw.command + cmd->count, 0, sizeof(cbw.command) - cmd->count);
236 
237 	werrstr("");		/* we use %r later even for n == 0 */
238 	if(diskdebug){
239 		fprint(2, "disk: cmd: tag %#lx: ", cbw.tag);
240 		for(n = 0; n < cbw.len; n++)
241 			fprint(2, " %2.2x", cbw.command[n]&0xFF);
242 		fprint(2, " datalen: %ld\n", cbw.datalen);
243 	}
244 
245 	/* issue tunnelled scsi command */
246 	if(write(ums->epout->dfd, &cbw, CbwLen) != CbwLen){
247 		fprint(2, "disk: cmd: %r\n");
248 		goto Fail;
249 	}
250 
251 	/* transfer the data */
252 	nio = data->count;
253 	if(nio != 0){
254 		if(data->write)
255 			n = write(ums->epout->dfd, data->p, nio);
256 		else{
257 			n = read(ums->epin->dfd, data->p, nio);
258 			left = nio - n;
259 			if (n >= 0 && left > 0)	/* didn't fill data->p? */
260 				memset(data->p + n, 0, left);
261 		}
262 		nio = n;
263 		if(diskdebug)
264 			if(n < 0)
265 				fprint(2, "disk: data: %r\n");
266 			else
267 				fprint(2, "disk: data: %d bytes\n", n);
268 		if(n <= 0)
269 			if(data->write == 0)
270 				unstall(ums->dev, ums->epin, Ein);
271 	}
272 
273 	/* read the transfer's status */
274 	n = read(ums->epin->dfd, &csw, CswLen);
275 	if(n <= 0){
276 		/* n == 0 means "stalled" */
277 		unstall(ums->dev, ums->epin, Ein);
278 		n = read(ums->epin->dfd, &csw, CswLen);
279 	}
280 
281 	if(n != CswLen || strncmp(csw.signature, "USBS", 4) != 0){
282 		dprint(2, "disk: read n=%d: status: %r\n", n);
283 		goto Fail;
284 	}
285 	if(csw.tag != cbw.tag){
286 		dprint(2, "disk: status tag mismatch\n");
287 		goto Fail;
288 	}
289 	if(csw.status >= CswPhaseErr){
290 		dprint(2, "disk: phase error\n");
291 		goto Fail;
292 	}
293 	if(csw.dataresidue == 0 || ums->wrongresidues)
294 		csw.dataresidue = data->count - nio;
295 	if(diskdebug){
296 		fprint(2, "disk: status: %2.2ux residue: %ld\n",
297 			csw.status, csw.dataresidue);
298 		if(cbw.command[0] == ScmdRsense){
299 			fprint(2, "sense data:");
300 			for(n = 0; n < data->count - csw.dataresidue; n++)
301 				fprint(2, " %2.2x", data->p[n]);
302 			fprint(2, "\n");
303 		}
304 	}
305 	switch(csw.status){
306 	case CswOk:
307 		*status = STok;
308 		break;
309 	case CswFailed:
310 		*status = STcheck;
311 		break;
312 	default:
313 		dprint(2, "disk: phase error\n");
314 		goto Fail;
315 	}
316 	ums->nerrs = 0;
317 	return data->count - csw.dataresidue;
318 
319 Fail:
320 	*status = STharderr;
321 	if(ums->nerrs++ > 15){
322 		fprint(2, "disk: %s: too many errors: device detached\n", ums->dev->dir);
323 		umsfatal(ums);
324 	}else
325 		umsrecover(ums);
326 	return -1;
327 }
328 
329 static int
330 dwalk(Usbfs *fs, Fid *fid, char *name)
331 {
332 	int i;
333 	Qid qid;
334 
335 	qid = fid->qid;
336 	if((qid.type & QTDIR) == 0){
337 		werrstr("walk in non-directory");
338 		return -1;
339 	}
340 
341 	if(strcmp(name, "..") == 0)
342 		return 0;
343 
344 	for(i = 1; i < nelem(dirtab); i++)
345 		if(strcmp(name, dirtab[i].name) == 0){
346 			qid.path = i | fs->qid;
347 			qid.vers = 0;
348 			qid.type = dirtab[i].mode >> 24;
349 			fid->qid = qid;
350 			return 0;
351 		}
352 	werrstr(Enotfound);
353 	return -1;
354 }
355 
356 static void
357 dostat(Usbfs *fs, int path, Dir *d)
358 {
359 	Dirtab *t;
360 	Umsc *lun;
361 
362 	t = &dirtab[path];
363 	d->qid.path = path;
364 	d->qid.type = t->mode >> 24;
365 	d->mode = t->mode;
366 	d->name = t->name;
367 	lun = fs->aux;
368 	if(path == Qdata)
369 		d->length = lun->capacity;
370 	else
371 		d->length = 0;
372 }
373 
374 static int
375 dirgen(Usbfs *fs, Qid, int i, Dir *d, void*)
376 {
377 	i++;	/* skip dir */
378 	if(i >= Qmax)
379 		return -1;
380 	else{
381 		dostat(fs, i, d);
382 		d->qid.path |= fs->qid;
383 		return 0;
384 	}
385 }
386 
387 static int
388 dstat(Usbfs *fs, Qid qid, Dir *d)
389 {
390 	int path;
391 
392 	path = qid.path & ~fs->qid;
393 	dostat(fs, path, d);
394 	d->qid.path |= fs->qid;
395 	return 0;
396 }
397 
398 static int
399 dopen(Usbfs *fs, Fid *fid, int)
400 {
401 	ulong path;
402 	Umsc *lun;
403 
404 	path = fid->qid.path & ~fs->qid;
405 	lun = fs->aux;
406 	switch(path){
407 	case Qraw:
408 		lun->phase = Pcmd;
409 		break;
410 	}
411 	return 0;
412 }
413 
414 /*
415  * check i/o parameters and compute values needed later.
416  * we shift & mask manually to avoid run-time calls to _divv and _modv,
417  * since we don't need general division nor its cost.
418  */
419 static int
420 setup(Umsc *lun, char *data, int count, vlong offset)
421 {
422 	long nb, lbsize, lbshift, lbmask;
423 	uvlong bno;
424 
425 	if(count < 0 || lun->lbsize <= 0 && umscapacity(lun) < 0 ||
426 	    lun->lbsize == 0)
427 		return -1;
428 	lbsize = lun->lbsize;
429 	assert(ispow2(lbsize));
430 	lbshift = log2(lbsize);
431 	lbmask = lbsize - 1;
432 
433 	bno = offset >> lbshift;	/* offset / lbsize */
434 	nb = ((offset + count + lbsize - 1) >> lbshift) - bno;
435 
436 	if(bno + nb > lun->blocks)		/* past end of device? */
437 		nb = lun->blocks - bno;
438 	if(nb * lbsize > Maxiosize)
439 		nb = Maxiosize / lbsize;
440 	lun->nb = nb;
441 	if(bno >= lun->blocks || nb == 0)
442 		return 0;
443 
444 	lun->offset = bno;
445 	lun->off = offset & lbmask;		/* offset % lbsize */
446 	if(lun->off == 0 && (count & lbmask) == 0)
447 		lun->bufp = data;
448 	else
449 		/* not transferring full, aligned blocks; need intermediary */
450 		lun->bufp = lun->buf;
451 	return count;
452 }
453 
454 /*
455  * Upon SRread/SRwrite errors we assume the medium may have changed,
456  * and ask again for the capacity of the media.
457  * BUG: How to proceed to avoid confusing dossrv??
458  *
459  * ctl reads must match the format documented in sd(3) exactly
460  * to interoperate with the rest of the system.
461  */
462 static long
463 dread(Usbfs *fs, Fid *fid, void *data, long count, vlong offset)
464 {
465 	long n;
466 	ulong path;
467 	char buf[1024];
468 	char *s, *e;
469 	Umsc *lun;
470 	Ums *ums;
471 	Qid q;
472 
473 	q = fid->qid;
474 	path = fid->qid.path & ~fs->qid;
475 	ums = fs->dev->aux;
476 	lun = fs->aux;
477 
478 	qlock(ums);
479 	switch(path){
480 	case Qdir:
481 		count = usbdirread(fs, q, data, count, offset, dirgen, nil);
482 		break;
483 	case Qctl:
484 		s = buf;
485 		e = buf + sizeof(buf);
486 		if(lun->flags & Finqok)
487 			s = seprint(s, e, "inquiry %s lun %ld: %s\n",
488 				fs->dev->dir, lun - &ums->lun[0], lun->inq);
489 		if(lun->blocks > 0)
490 			s = seprint(s, e, "geometry %llud %ld\n",
491 				lun->blocks, lun->lbsize);
492 		count = usbreadbuf(data, count, offset, buf, s - buf);
493 		break;
494 	case Qraw:
495 		if(lun->lbsize <= 0 && umscapacity(lun) < 0){
496 			count = -1;
497 			break;
498 		}
499 		switch(lun->phase){
500 		case Pcmd:
501 			qunlock(ums);
502 			werrstr("phase error");
503 			return -1;
504 		case Pdata:
505 			lun->data.p = data;
506 			lun->data.count = count;
507 			lun->data.write = 0;
508 			count = umsrequest(lun,&lun->cmd,&lun->data,&lun->status);
509 			lun->phase = Pstatus;
510 			if(count < 0)
511 				lun->lbsize = 0;  /* medium may have changed */
512 			break;
513 		case Pstatus:
514 			n = snprint(buf, sizeof buf, "%11.0ud ", lun->status);
515 			count = usbreadbuf(data, count, 0LL, buf, n);
516 			lun->phase = Pcmd;
517 			break;
518 		}
519 		break;
520 	case Qdata:
521 		count = setup(lun, data, count, offset);
522 		if (count <= 0)
523 			break;
524 		n = SRread(lun, lun->bufp, lun->nb * lun->lbsize);
525 		if(n < 0){
526 			lun->lbsize = 0;	/* medium may have changed */
527 			count = -1;
528 		} else if (lun->bufp == data)
529 			count = n;
530 		else{
531 			/*
532 			 * if n == lun->nb*lun->lbsize (as expected),
533 			 * just copy count bytes.
534 			 */
535 			if(lun->off + count > n)
536 				count = n - lun->off; /* short read */
537 			if(count > 0)
538 				memmove(data, lun->bufp + lun->off, count);
539 		}
540 		break;
541 	}
542 	qunlock(ums);
543 	return count;
544 }
545 
546 static long
547 dwrite(Usbfs *fs, Fid *fid, void *data, long count, vlong offset)
548 {
549 	long len, ocount;
550 	ulong path;
551 	uvlong bno;
552 	Ums *ums;
553 	Umsc *lun;
554 
555 	ums = fs->dev->aux;
556 	lun = fs->aux;
557 	path = fid->qid.path & ~fs->qid;
558 
559 	qlock(ums);
560 	switch(path){
561 	default:
562 		werrstr(Eperm);
563 		count = -1;
564 		break;
565 	case Qctl:
566 		dprint(2, "usb/disk: ctl ignored\n");
567 		break;
568 	case Qraw:
569 		if(lun->lbsize <= 0 && umscapacity(lun) < 0){
570 			count = -1;
571 			break;
572 		}
573 		switch(lun->phase){
574 		case Pcmd:
575 			if(count != 6 && count != 10){
576 				qunlock(ums);
577 				werrstr("bad command length");
578 				return -1;
579 			}
580 			memmove(lun->rawcmd, data, count);
581 			lun->cmd.p = lun->rawcmd;
582 			lun->cmd.count = count;
583 			lun->cmd.write = 1;
584 			lun->phase = Pdata;
585 			break;
586 		case Pdata:
587 			lun->data.p = data;
588 			lun->data.count = count;
589 			lun->data.write = 1;
590 			count = umsrequest(lun,&lun->cmd,&lun->data,&lun->status);
591 			lun->phase = Pstatus;
592 			if(count < 0)
593 				lun->lbsize = 0;  /* medium may have changed */
594 			break;
595 		case Pstatus:
596 			lun->phase = Pcmd;
597 			werrstr("phase error");
598 			count = -1;
599 			break;
600 		}
601 		break;
602 	case Qdata:
603 		len = ocount = count;
604 		count = setup(lun, data, count, offset);
605 		if (count <= 0)
606 			break;
607 		bno = lun->offset;
608 		if (lun->bufp == lun->buf) {
609 			count = SRread(lun, lun->bufp, lun->nb * lun->lbsize);
610 			if(count < 0) {
611 				lun->lbsize = 0;  /* medium may have changed */
612 				break;
613 			}
614 			/*
615 			 * if count == lun->nb*lun->lbsize, as expected, just
616 			 * copy len (the original count) bytes of user data.
617 			 */
618 			if(lun->off + len > count)
619 				len = count - lun->off; /* short read */
620 			if(len > 0)
621 				memmove(lun->bufp + lun->off, data, len);
622 		}
623 
624 		lun->offset = bno;
625 		count = SRwrite(lun, lun->bufp, lun->nb * lun->lbsize);
626 		if(count < 0)
627 			lun->lbsize = 0;	/* medium may have changed */
628 		else{
629 			if(lun->off + len > count)
630 				count -= lun->off; /* short write */
631 			/* never report more bytes written than requested */
632 			if(count < 0)
633 				count = 0;
634 			else if(count > ocount)
635 				count = ocount;
636 		}
637 		break;
638 	}
639 	qunlock(ums);
640 	return count;
641 }
642 
643 int
644 findendpoints(Ums *ums)
645 {
646 	Ep *ep;
647 	Usbdev *ud;
648 	ulong csp, sc;
649 	int i, epin, epout;
650 
651 	epin = epout = -1;
652 	ud = ums->dev->usb;
653 	for(i = 0; i < nelem(ud->ep); i++){
654 		if((ep = ud->ep[i]) == nil)
655 			continue;
656 		csp = ep->iface->csp;
657 		sc = Subclass(csp);
658 		if(!(Class(csp) == Clstorage && (Proto(csp) == Protobulk)))
659 			continue;
660 		if(sc != Subatapi && sc != Sub8070 && sc != Subscsi)
661 			fprint(2, "disk: subclass %#ulx not supported. trying anyway\n", sc);
662 		if(ep->type == Ebulk){
663 			if(ep->dir == Eboth || ep->dir == Ein)
664 				if(epin == -1)
665 					epin =  ep->id;
666 			if(ep->dir == Eboth || ep->dir == Eout)
667 				if(epout == -1)
668 					epout = ep->id;
669 		}
670 	}
671 	dprint(2, "disk: ep ids: in %d out %d\n", epin, epout);
672 	if(epin == -1 || epout == -1)
673 		return -1;
674 	ums->epin = openep(ums->dev, epin);
675 	if(ums->epin == nil){
676 		fprint(2, "disk: openep %d: %r\n", epin);
677 		return -1;
678 	}
679 	if(epout == epin){
680 		incref(ums->epin);
681 		ums->epout = ums->epin;
682 	}else
683 		ums->epout = openep(ums->dev, epout);
684 	if(ums->epout == nil){
685 		fprint(2, "disk: openep %d: %r\n", epout);
686 		closedev(ums->epin);
687 		return -1;
688 	}
689 	if(ums->epin == ums->epout)
690 		opendevdata(ums->epin, ORDWR);
691 	else{
692 		opendevdata(ums->epin, OREAD);
693 		opendevdata(ums->epout, OWRITE);
694 	}
695 	if(ums->epin->dfd < 0 || ums->epout->dfd < 0){
696 		fprint(2, "disk: open i/o ep data: %r\n");
697 		closedev(ums->epin);
698 		closedev(ums->epout);
699 		return -1;
700 	}
701 	dprint(2, "disk: ep in %s out %s\n", ums->epin->dir, ums->epout->dir);
702 
703 	devctl(ums->epin, "timeout 2000");
704 	devctl(ums->epout, "timeout 2000");
705 
706 	if(usbdebug > 1 || diskdebug > 2){
707 		devctl(ums->epin, "debug 1");
708 		devctl(ums->epout, "debug 1");
709 		devctl(ums->dev, "debug 1");
710 	}
711 	return 0;
712 }
713 
714 static int
715 usage(void)
716 {
717 	werrstr("usage: usb/disk [-d] [-N nb]");
718 	return -1;
719 }
720 
721 static void
722 umsdevfree(void *a)
723 {
724 	Ums *ums = a;
725 
726 	if(ums == nil)
727 		return;
728 	closedev(ums->epin);
729 	closedev(ums->epout);
730 	ums->epin = ums->epout = nil;
731 	free(ums->lun);
732 	free(ums);
733 }
734 
735 static Usbfs diskfs = {
736 	.walk = dwalk,
737 	.open =	 dopen,
738 	.read =	 dread,
739 	.write = dwrite,
740 	.stat =	 dstat,
741 };
742 
743 int
744 diskmain(Dev *dev, int argc, char **argv)
745 {
746 	Ums *ums;
747 	Umsc *lun;
748 	int i, devid;
749 
750 	devid = dev->id;
751 	ARGBEGIN{
752 	case 'd':
753 		scsidebug(diskdebug);
754 		diskdebug++;
755 		break;
756 	case 'N':
757 		devid = atoi(EARGF(usage()));
758 		break;
759 	default:
760 		return usage();
761 	}ARGEND
762 	if(argc != 0) {
763 		return usage();
764 	}
765 
766 //	notify(ding);
767 	ums = dev->aux = emallocz(sizeof(Ums), 1);
768 	ums->maxlun = -1;
769 	ums->dev = dev;
770 	dev->free = umsdevfree;
771 	if(findendpoints(ums) < 0){
772 		werrstr("disk: endpoints not found");
773 		return -1;
774 	}
775 
776 	/*
777 	 * SanDISK 512M gets residues wrong.
778 	 */
779 	if(dev->usb->vid == 0x0781 && dev->usb->did == 0x5150)
780 		ums->wrongresidues = 1;
781 
782 	if(umsinit(ums) < 0){
783 		dprint(2, "disk: umsinit: %r\n");
784 		return -1;
785 	}
786 
787 	for(i = 0; i <= ums->maxlun; i++){
788 		lun = &ums->lun[i];
789 		lun->fs = diskfs;
790 		snprint(lun->fs.name, sizeof(lun->fs.name), "sdU%d.%d", devid, i);
791 		lun->fs.dev = dev;
792 		incref(dev);
793 		lun->fs.aux = lun;
794 		usbfsadd(&lun->fs);
795 	}
796 	return 0;
797 }
798