xref: /aosp_15_r20/external/libusb/libusb/os/netbsd_usb.c (revision 86b64dcb59b3a0b37502ecd56e119234366a6f7e)
1 /*
2  * Copyright © 2011 Martin Pieuchot <[email protected]>
3  *
4  * This library is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * This library is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with this library; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include <config.h>
20 
21 #include <sys/time.h>
22 #include <sys/types.h>
23 
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <unistd.h>
30 
31 #include <dev/usb/usb.h>
32 
33 #include "libusbi.h"
34 
35 struct device_priv {
36 	char devnode[16];
37 	int fd;
38 
39 	usb_config_descriptor_t *cdesc;		/* active config descriptor */
40 };
41 
42 struct handle_priv {
43 	int endpoints[USB_MAX_ENDPOINTS];
44 };
45 
46 /*
47  * Backend functions
48  */
49 static int netbsd_get_device_list(struct libusb_context *,
50     struct discovered_devs **);
51 static int netbsd_open(struct libusb_device_handle *);
52 static void netbsd_close(struct libusb_device_handle *);
53 
54 static int netbsd_get_active_config_descriptor(struct libusb_device *,
55     void *, size_t);
56 static int netbsd_get_config_descriptor(struct libusb_device *, uint8_t,
57     void *, size_t);
58 
59 static int netbsd_get_configuration(struct libusb_device_handle *, uint8_t *);
60 static int netbsd_set_configuration(struct libusb_device_handle *, int);
61 
62 static int netbsd_claim_interface(struct libusb_device_handle *, uint8_t);
63 static int netbsd_release_interface(struct libusb_device_handle *, uint8_t);
64 
65 static int netbsd_set_interface_altsetting(struct libusb_device_handle *,
66     uint8_t, uint8_t);
67 static int netbsd_clear_halt(struct libusb_device_handle *, unsigned char);
68 static void netbsd_destroy_device(struct libusb_device *);
69 
70 static int netbsd_submit_transfer(struct usbi_transfer *);
71 static int netbsd_cancel_transfer(struct usbi_transfer *);
72 static int netbsd_handle_transfer_completion(struct usbi_transfer *);
73 
74 /*
75  * Private functions
76  */
77 static int _errno_to_libusb(int);
78 static int _cache_active_config_descriptor(struct libusb_device *, int);
79 static int _sync_control_transfer(struct usbi_transfer *);
80 static int _sync_gen_transfer(struct usbi_transfer *);
81 static int _access_endpoint(struct libusb_transfer *);
82 
83 const struct usbi_os_backend usbi_backend = {
84 	.name = "Synchronous NetBSD backend",
85 	.caps = 0,
86 	.get_device_list = netbsd_get_device_list,
87 	.open = netbsd_open,
88 	.close = netbsd_close,
89 
90 	.get_active_config_descriptor = netbsd_get_active_config_descriptor,
91 	.get_config_descriptor = netbsd_get_config_descriptor,
92 
93 	.get_configuration = netbsd_get_configuration,
94 	.set_configuration = netbsd_set_configuration,
95 
96 	.claim_interface = netbsd_claim_interface,
97 	.release_interface = netbsd_release_interface,
98 
99 	.set_interface_altsetting = netbsd_set_interface_altsetting,
100 	.clear_halt = netbsd_clear_halt,
101 
102 	.destroy_device = netbsd_destroy_device,
103 
104 	.submit_transfer = netbsd_submit_transfer,
105 	.cancel_transfer = netbsd_cancel_transfer,
106 
107 	.handle_transfer_completion = netbsd_handle_transfer_completion,
108 
109 	.device_priv_size = sizeof(struct device_priv),
110 	.device_handle_priv_size = sizeof(struct handle_priv),
111 };
112 
113 int
netbsd_get_device_list(struct libusb_context * ctx,struct discovered_devs ** discdevs)114 netbsd_get_device_list(struct libusb_context * ctx,
115 	struct discovered_devs **discdevs)
116 {
117 	struct libusb_device *dev;
118 	struct device_priv *dpriv;
119 	struct usb_device_info di;
120 	usb_device_descriptor_t ddesc;
121 	unsigned long session_id;
122 	char devnode[16];
123 	int fd, err, i;
124 
125 	usbi_dbg(ctx, " ");
126 
127 	/* Only ugen(4) is supported */
128 	for (i = 0; i < USB_MAX_DEVICES; i++) {
129 		/* Control endpoint is always .00 */
130 		snprintf(devnode, sizeof(devnode), "/dev/ugen%d.00", i);
131 
132 		if ((fd = open(devnode, O_RDONLY)) < 0) {
133 			if (errno != ENOENT && errno != ENXIO)
134 				usbi_err(ctx, "could not open %s", devnode);
135 			continue;
136 		}
137 
138 		if (ioctl(fd, USB_GET_DEVICEINFO, &di) < 0)
139 			continue;
140 
141 		session_id = (di.udi_bus << 8 | di.udi_addr);
142 		dev = usbi_get_device_by_session_id(ctx, session_id);
143 
144 		if (dev == NULL) {
145 			dev = usbi_alloc_device(ctx, session_id);
146 			if (dev == NULL)
147 				return LIBUSB_ERROR_NO_MEM;
148 
149 			dev->bus_number = 1 + di.udi_bus;
150 			dev->device_address = 1 + di.udi_addr;
151 			dev->speed = di.udi_speed; /* NetBSD #define's happen to match libusb enum */
152 
153 			dpriv = usbi_get_device_priv(dev);
154 			strlcpy(dpriv->devnode, devnode, sizeof(devnode));
155 			dpriv->fd = -1;
156 
157 			if (ioctl(fd, USB_GET_DEVICE_DESC, &ddesc) < 0) {
158 				err = errno;
159 				goto error;
160 			}
161 
162 			static_assert(sizeof(dev->device_descriptor) == sizeof(ddesc),
163 				      "mismatch between libusb and OS device descriptor sizes");
164 			memcpy(&dev->device_descriptor, &ddesc, LIBUSB_DT_DEVICE_SIZE);
165 			usbi_localize_device_descriptor(&dev->device_descriptor);
166 
167 			if (_cache_active_config_descriptor(dev, fd)) {
168 				err = errno;
169 				goto error;
170 			}
171 
172 			if ((err = usbi_sanitize_device(dev)))
173 				goto error;
174 		}
175 		close(fd);
176 
177 		if (discovered_devs_append(*discdevs, dev) == NULL)
178 			return LIBUSB_ERROR_NO_MEM;
179 
180 		libusb_unref_device(dev);
181 	}
182 
183 	return LIBUSB_SUCCESS;
184 
185 error:
186 	close(fd);
187 	libusb_unref_device(dev);
188 	return _errno_to_libusb(err);
189 }
190 
191 int
netbsd_open(struct libusb_device_handle * handle)192 netbsd_open(struct libusb_device_handle *handle)
193 {
194 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
195 	struct handle_priv *hpriv = usbi_get_device_handle_priv(handle);
196 	int i;
197 
198 	dpriv->fd = open(dpriv->devnode, O_RDWR);
199 	if (dpriv->fd < 0) {
200 		dpriv->fd = open(dpriv->devnode, O_RDONLY);
201 		if (dpriv->fd < 0)
202 			return _errno_to_libusb(errno);
203 	}
204 
205 	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
206 		hpriv->endpoints[i] = -1;
207 
208 	usbi_dbg(HANDLE_CTX(handle), "open %s: fd %d", dpriv->devnode, dpriv->fd);
209 
210 	return LIBUSB_SUCCESS;
211 }
212 
213 void
netbsd_close(struct libusb_device_handle * handle)214 netbsd_close(struct libusb_device_handle *handle)
215 {
216 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
217 
218 	usbi_dbg(HANDLE_CTX(handle), "close: fd %d", dpriv->fd);
219 
220 	close(dpriv->fd);
221 	dpriv->fd = -1;
222 }
223 
224 int
netbsd_get_active_config_descriptor(struct libusb_device * dev,void * buf,size_t len)225 netbsd_get_active_config_descriptor(struct libusb_device *dev,
226     void *buf, size_t len)
227 {
228 	struct device_priv *dpriv = usbi_get_device_priv(dev);
229 
230 	len = MIN(len, (size_t)UGETW(dpriv->cdesc->wTotalLength));
231 
232 	usbi_dbg(DEVICE_CTX(dev), "len %zu", len);
233 
234 	memcpy(buf, dpriv->cdesc, len);
235 
236 	return (int)len;
237 }
238 
239 int
netbsd_get_config_descriptor(struct libusb_device * dev,uint8_t idx,void * buf,size_t len)240 netbsd_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
241     void *buf, size_t len)
242 {
243 	struct device_priv *dpriv = usbi_get_device_priv(dev);
244 	struct usb_full_desc ufd;
245 	int fd, err;
246 
247 	usbi_dbg(DEVICE_CTX(dev), "index %u, len %zu", idx, len);
248 
249 	/* A config descriptor may be requested before opening the device */
250 	if (dpriv->fd >= 0) {
251 		fd = dpriv->fd;
252 	} else {
253 		fd = open(dpriv->devnode, O_RDONLY);
254 		if (fd < 0)
255 			return _errno_to_libusb(errno);
256 	}
257 
258 	ufd.ufd_config_index = idx;
259 	ufd.ufd_size = len;
260 	ufd.ufd_data = buf;
261 
262 	if (ioctl(fd, USB_GET_FULL_DESC, &ufd) < 0) {
263 		err = errno;
264 		if (dpriv->fd < 0)
265 			close(fd);
266 		return _errno_to_libusb(err);
267 	}
268 
269 	if (dpriv->fd < 0)
270 		close(fd);
271 
272 	return (int)len;
273 }
274 
275 int
netbsd_get_configuration(struct libusb_device_handle * handle,uint8_t * config)276 netbsd_get_configuration(struct libusb_device_handle *handle, uint8_t *config)
277 {
278 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
279 	int tmp;
280 
281 	usbi_dbg(HANDLE_CTX(handle), " ");
282 
283 	if (ioctl(dpriv->fd, USB_GET_CONFIG, &tmp) < 0)
284 		return _errno_to_libusb(errno);
285 
286 	usbi_dbg(HANDLE_CTX(handle), "configuration %d", tmp);
287 	*config = (uint8_t)tmp;
288 
289 	return LIBUSB_SUCCESS;
290 }
291 
292 int
netbsd_set_configuration(struct libusb_device_handle * handle,int config)293 netbsd_set_configuration(struct libusb_device_handle *handle, int config)
294 {
295 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
296 
297 	usbi_dbg(HANDLE_CTX(handle), "configuration %d", config);
298 
299 	if (ioctl(dpriv->fd, USB_SET_CONFIG, &config) < 0)
300 		return _errno_to_libusb(errno);
301 
302 	return _cache_active_config_descriptor(handle->dev, dpriv->fd);
303 }
304 
305 int
netbsd_claim_interface(struct libusb_device_handle * handle,uint8_t iface)306 netbsd_claim_interface(struct libusb_device_handle *handle, uint8_t iface)
307 {
308 	struct handle_priv *hpriv = usbi_get_device_handle_priv(handle);
309 	int i;
310 
311 	UNUSED(iface);
312 
313 	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
314 		hpriv->endpoints[i] = -1;
315 
316 	return LIBUSB_SUCCESS;
317 }
318 
319 int
netbsd_release_interface(struct libusb_device_handle * handle,uint8_t iface)320 netbsd_release_interface(struct libusb_device_handle *handle, uint8_t iface)
321 {
322 	struct handle_priv *hpriv = usbi_get_device_handle_priv(handle);
323 	int i;
324 
325 	UNUSED(iface);
326 
327 	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
328 		if (hpriv->endpoints[i] >= 0)
329 			close(hpriv->endpoints[i]);
330 
331 	return LIBUSB_SUCCESS;
332 }
333 
334 int
netbsd_set_interface_altsetting(struct libusb_device_handle * handle,uint8_t iface,uint8_t altsetting)335 netbsd_set_interface_altsetting(struct libusb_device_handle *handle, uint8_t iface,
336     uint8_t altsetting)
337 {
338 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
339 	struct usb_alt_interface intf;
340 
341 	usbi_dbg(HANDLE_CTX(handle), "iface %u, setting %u", iface, altsetting);
342 
343 	memset(&intf, 0, sizeof(intf));
344 
345 	intf.uai_interface_index = iface;
346 	intf.uai_alt_no = altsetting;
347 
348 	if (ioctl(dpriv->fd, USB_SET_ALTINTERFACE, &intf) < 0)
349 		return _errno_to_libusb(errno);
350 
351 	return LIBUSB_SUCCESS;
352 }
353 
354 int
netbsd_clear_halt(struct libusb_device_handle * handle,unsigned char endpoint)355 netbsd_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
356 {
357 	struct device_priv *dpriv = usbi_get_device_priv(handle->dev);
358 	struct usb_ctl_request req;
359 
360 	usbi_dbg(HANDLE_CTX(handle), " ");
361 
362 	req.ucr_request.bmRequestType = UT_WRITE_ENDPOINT;
363 	req.ucr_request.bRequest = UR_CLEAR_FEATURE;
364 	USETW(req.ucr_request.wValue, UF_ENDPOINT_HALT);
365 	USETW(req.ucr_request.wIndex, endpoint);
366 	USETW(req.ucr_request.wLength, 0);
367 
368 	if (ioctl(dpriv->fd, USB_DO_REQUEST, &req) < 0)
369 		return _errno_to_libusb(errno);
370 
371 	return LIBUSB_SUCCESS;
372 }
373 
374 void
netbsd_destroy_device(struct libusb_device * dev)375 netbsd_destroy_device(struct libusb_device *dev)
376 {
377 	struct device_priv *dpriv = usbi_get_device_priv(dev);
378 
379 	usbi_dbg(DEVICE_CTX(dev), " ");
380 
381 	free(dpriv->cdesc);
382 }
383 
384 int
netbsd_submit_transfer(struct usbi_transfer * itransfer)385 netbsd_submit_transfer(struct usbi_transfer *itransfer)
386 {
387 	struct libusb_transfer *transfer;
388 	int err = 0;
389 
390 	usbi_dbg(ITRANSFER_CTX(itransfer), " ");
391 
392 	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
393 
394 	switch (transfer->type) {
395 	case LIBUSB_TRANSFER_TYPE_CONTROL:
396 		err = _sync_control_transfer(itransfer);
397 		break;
398 	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
399 		if (IS_XFEROUT(transfer)) {
400 			/* Isochronous write is not supported */
401 			err = LIBUSB_ERROR_NOT_SUPPORTED;
402 			break;
403 		}
404 		err = _sync_gen_transfer(itransfer);
405 		break;
406 	case LIBUSB_TRANSFER_TYPE_BULK:
407 	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
408 		if (IS_XFEROUT(transfer) &&
409 		    transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
410 			err = LIBUSB_ERROR_NOT_SUPPORTED;
411 			break;
412 		}
413 		err = _sync_gen_transfer(itransfer);
414 		break;
415 	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
416 		err = LIBUSB_ERROR_NOT_SUPPORTED;
417 		break;
418 	}
419 
420 	if (err)
421 		return err;
422 
423 	usbi_signal_transfer_completion(itransfer);
424 
425 	return LIBUSB_SUCCESS;
426 }
427 
428 int
netbsd_cancel_transfer(struct usbi_transfer * itransfer)429 netbsd_cancel_transfer(struct usbi_transfer *itransfer)
430 {
431 	UNUSED(itransfer);
432 
433 	usbi_dbg(ITRANSFER_CTX(itransfer), " ");
434 
435 	return LIBUSB_ERROR_NOT_SUPPORTED;
436 }
437 
438 int
netbsd_handle_transfer_completion(struct usbi_transfer * itransfer)439 netbsd_handle_transfer_completion(struct usbi_transfer *itransfer)
440 {
441 	return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_COMPLETED);
442 }
443 
444 int
_errno_to_libusb(int err)445 _errno_to_libusb(int err)
446 {
447 	usbi_dbg(NULL, "error: %s (%d)", strerror(err), err);
448 
449 	switch (err) {
450 	case EIO:
451 		return LIBUSB_ERROR_IO;
452 	case EACCES:
453 		return LIBUSB_ERROR_ACCESS;
454 	case ENOENT:
455 		return LIBUSB_ERROR_NO_DEVICE;
456 	case ENOMEM:
457 		return LIBUSB_ERROR_NO_MEM;
458 	case EWOULDBLOCK:
459 	case ETIMEDOUT:
460 		return LIBUSB_ERROR_TIMEOUT;
461 	default:
462 		return LIBUSB_ERROR_OTHER;
463 	}
464 }
465 
466 int
_cache_active_config_descriptor(struct libusb_device * dev,int fd)467 _cache_active_config_descriptor(struct libusb_device *dev, int fd)
468 {
469 	struct device_priv *dpriv = usbi_get_device_priv(dev);
470 	struct usb_config_desc ucd;
471 	struct usb_full_desc ufd;
472 	void *buf;
473 	int len;
474 
475 	usbi_dbg(DEVICE_CTX(dev), "fd %d", fd);
476 
477 	ucd.ucd_config_index = USB_CURRENT_CONFIG_INDEX;
478 
479 	if (ioctl(fd, USB_GET_CONFIG_DESC, &ucd) < 0)
480 		return _errno_to_libusb(errno);
481 
482 	usbi_dbg(DEVICE_CTX(dev), "active bLength %d", ucd.ucd_desc.bLength);
483 
484 	len = UGETW(ucd.ucd_desc.wTotalLength);
485 	buf = malloc((size_t)len);
486 	if (buf == NULL)
487 		return LIBUSB_ERROR_NO_MEM;
488 
489 	ufd.ufd_config_index = ucd.ucd_config_index;
490 	ufd.ufd_size = len;
491 	ufd.ufd_data = buf;
492 
493 	usbi_dbg(DEVICE_CTX(dev), "index %d, len %d", ufd.ufd_config_index, len);
494 
495 	if (ioctl(fd, USB_GET_FULL_DESC, &ufd) < 0) {
496 		free(buf);
497 		return _errno_to_libusb(errno);
498 	}
499 
500 	if (dpriv->cdesc)
501 		free(dpriv->cdesc);
502 	dpriv->cdesc = buf;
503 
504 	return 0;
505 }
506 
507 int
_sync_control_transfer(struct usbi_transfer * itransfer)508 _sync_control_transfer(struct usbi_transfer *itransfer)
509 {
510 	struct libusb_transfer *transfer;
511 	struct libusb_control_setup *setup;
512 	struct device_priv *dpriv;
513 	struct usb_ctl_request req;
514 
515 	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
516 	dpriv = usbi_get_device_priv(transfer->dev_handle->dev);
517 	setup = (struct libusb_control_setup *)transfer->buffer;
518 
519 	usbi_dbg(ITRANSFER_CTX(itransfer), "type 0x%x request 0x%x value 0x%x index %d length %d timeout %d",
520 	    setup->bmRequestType, setup->bRequest,
521 	    libusb_le16_to_cpu(setup->wValue),
522 	    libusb_le16_to_cpu(setup->wIndex),
523 	    libusb_le16_to_cpu(setup->wLength), transfer->timeout);
524 
525 	req.ucr_request.bmRequestType = setup->bmRequestType;
526 	req.ucr_request.bRequest = setup->bRequest;
527 	/* Don't use USETW, libusb already deals with the endianness */
528 	(*(uint16_t *)req.ucr_request.wValue) = setup->wValue;
529 	(*(uint16_t *)req.ucr_request.wIndex) = setup->wIndex;
530 	(*(uint16_t *)req.ucr_request.wLength) = setup->wLength;
531 	req.ucr_data = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
532 
533 	if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
534 		req.ucr_flags = USBD_SHORT_XFER_OK;
535 
536 	if (ioctl(dpriv->fd, USB_SET_TIMEOUT, &transfer->timeout) < 0)
537 		return _errno_to_libusb(errno);
538 
539 	if (ioctl(dpriv->fd, USB_DO_REQUEST, &req) < 0)
540 		return _errno_to_libusb(errno);
541 
542 	itransfer->transferred = req.ucr_actlen;
543 
544 	usbi_dbg(ITRANSFER_CTX(itransfer), "transferred %d", itransfer->transferred);
545 
546 	return 0;
547 }
548 
549 int
_access_endpoint(struct libusb_transfer * transfer)550 _access_endpoint(struct libusb_transfer *transfer)
551 {
552 	struct handle_priv *hpriv;
553 	struct device_priv *dpriv;
554 	char *s, devnode[16];
555 	int fd, endpt;
556 	mode_t mode;
557 
558 	hpriv = usbi_get_device_handle_priv(transfer->dev_handle);
559 	dpriv = usbi_get_device_priv(transfer->dev_handle->dev);
560 
561 	endpt = UE_GET_ADDR(transfer->endpoint);
562 	mode = IS_XFERIN(transfer) ? O_RDONLY : O_WRONLY;
563 
564 	usbi_dbg(TRANSFER_CTX(transfer), "endpoint %d mode %d", endpt, mode);
565 
566 	if (hpriv->endpoints[endpt] < 0) {
567 		/* Pick the right node given the control one */
568 		strlcpy(devnode, dpriv->devnode, sizeof(devnode));
569 		s = strchr(devnode, '.');
570 		snprintf(s, 4, ".%02d", endpt);
571 
572 		/* We may need to read/write to the same endpoint later. */
573 		if (((fd = open(devnode, O_RDWR)) < 0) && (errno == ENXIO))
574 			if ((fd = open(devnode, mode)) < 0)
575 				return -1;
576 
577 		hpriv->endpoints[endpt] = fd;
578 	}
579 
580 	return hpriv->endpoints[endpt];
581 }
582 
583 int
_sync_gen_transfer(struct usbi_transfer * itransfer)584 _sync_gen_transfer(struct usbi_transfer *itransfer)
585 {
586 	struct libusb_transfer *transfer;
587 	int fd, nr = 1;
588 
589 	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
590 
591 	/*
592 	 * Bulk, Interrupt or Isochronous transfer depends on the
593 	 * endpoint and thus the node to open.
594 	 */
595 	if ((fd = _access_endpoint(transfer)) < 0)
596 		return _errno_to_libusb(errno);
597 
598 	if (ioctl(fd, USB_SET_TIMEOUT, &transfer->timeout) < 0)
599 		return _errno_to_libusb(errno);
600 
601 	if (IS_XFERIN(transfer)) {
602 		if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
603 			if (ioctl(fd, USB_SET_SHORT_XFER, &nr) < 0)
604 				return _errno_to_libusb(errno);
605 
606 		nr = read(fd, transfer->buffer, transfer->length);
607 	} else {
608 		nr = write(fd, transfer->buffer, transfer->length);
609 	}
610 
611 	if (nr < 0)
612 		return _errno_to_libusb(errno);
613 
614 	itransfer->transferred = nr;
615 
616 	return 0;
617 }
618