2 * I/O functions for libusb
3 * Copyright (C) 2007-2008 Daniel Drake <dsd@gentoo.org>
4 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28 #include <sys/select.h>
35 /* this is a list of in-flight rb_handles, sorted by timeout expiration.
36 * URBs to timeout the soonest are placed at the beginning of the list, URBs
37 * that will time out later are placed after, and urbs with infinite timeout
38 * are always placed at the very end. */
39 static struct list_head flying_transfers;
41 /* list of poll fd's */
42 static struct list_head pollfds;
44 /* user callbacks for pollfd changes */
45 static libusb_pollfd_added_cb fd_added_cb = NULL;
46 static libusb_pollfd_removed_cb fd_removed_cb = NULL;
49 * \page io Synchronous and asynchronous device I/O
51 * \section intro Introduction
53 * If you're using libusb in your application, you're probably wanting to
54 * perform I/O with devices - you want to perform USB data transfers.
56 * libusb offers two separate interfaces for device I/O. This page aims to
57 * introduce the two in order to help you decide which one is more suitable
58 * for your application. You can also choose to use both interfaces in your
59 * application by considering each transfer on a case-by-case basis.
61 * Once you have read through the following discussion, you should consult the
62 * detailed API documentation pages for the details:
66 * \section theory Transfers at a logical level
68 * At a logical level, USB transfers typically happen in two parts. For
69 * example, when reading data from a endpoint:
70 * -# A request for data is sent to the device
71 * -# Some time later, the incoming data is received by the host
73 * or when writing data to an endpoint:
75 * -# The data is sent to the device
76 * -# Some time later, the host receives acknowledgement from the device that
77 * the data has been transferred.
79 * There may be an indefinite delay between the two steps. Consider a
80 * fictional USB input device with a button that the user can press. In order
81 * to determine when the button is pressed, you would likely submit a request
82 * to read data on a bulk or interrupt endpoint and wait for data to arrive.
83 * Data will arrive when the button is pressed by the user, which is
84 * potentially hours later.
86 * libusb offers both a synchronous and an asynchronous interface to performing
87 * USB transfers. The main difference is that the synchronous interface
88 * combines both steps indicated above into a single function call, whereas
89 * the asynchronous interface separates them.
91 * \section sync The synchronous interface
93 * The synchronous I/O interface allows you to perform a USB transfer with
94 * a single function call. When the function call returns, the transfer has
95 * completed and you can parse the results.
97 * If you have used the libusb-0.1 before, this I/O style will seem familar to
98 * you. libusb-0.1 only offered a synchronous interface.
100 * In our input device example, to read button presses you might write code
101 * in the following style:
103 unsigned char data[4];
105 int r = libusb_bulk_transfer(handle, EP_IN, data, sizeof(data), &actual_length, 0);
106 if (r == 0 && actual_length == sizeof(data)) {
107 // results of the transaction can now be found in the data buffer
108 // parse them here and report button press
114 * The main advantage of this model is simplicity: you did everything with
115 * a single simple function call.
117 * However, this interface has its limitations. Your application will sleep
118 * inside libusb_bulk_transfer() until the transaction has completed. If it
119 * takes the user 3 hours to press the button, your application will be
120 * sleeping for that long. Execution will be tied up inside the library -
121 * the entire thread will be useless for that duration.
123 * Another issue is that by tieing up the thread with that single transaction
124 * there is no possibility of performing I/O with multiple endpoints and/or
125 * multiple devices simultaneously, unless you resort to creating one thread
128 * Additionally, there is no opportunity to cancel the transfer after the
129 * request has been submitted.
131 * For details on how to use the synchronous API, see the
132 * \ref syncio "synchronous I/O API documentation" pages.
134 * \section async The asynchronous interface
136 * Asynchronous I/O is the most significant new feature in libusb-1.0.
137 * Although it is a more complex interface, it solves all the issues detailed
140 * Instead of providing which functions that block until the I/O has complete,
141 * libusb's asynchronous interface presents non-blocking functions which
142 * begin a transfer and then return immediately. Your application passes a
143 * callback function pointer to this non-blocking function, which libusb will
144 * call with the results of the transaction when it has completed.
146 * Transfers which have been submitted through the non-blocking functions
147 * can be cancelled with a separate function call.
149 * The non-blocking nature of this interface allows you to be simultaneously
150 * performing I/O to multiple endpoints on multiple devices, without having
153 * This added flexibility does come with some complications though:
154 * - In the interest of being a lightweight library, libusb does not create
155 * threads and can only operate when your application is calling into it. Your
156 * application must call into libusb from it's main loop when events are ready
157 * to be handled, or you must use some other scheme to allow libusb to
158 * undertake whatever work needs to be done.
159 * - libusb also needs to be called into at certain fixed points in time in
160 * order to accurately handle transfer timeouts.
161 * - Memory handling becomes more complex. You cannot use stack memory unless
162 * the function with that stack is guaranteed not to return until the transfer
163 * callback has finished executing.
164 * - You generally lose some linearity from your code flow because submitting
165 * the transfer request is done in a separate function from where the transfer
166 * results are handled. This becomes particularly obvious when you want to
167 * submit a second transfer based on the results of an earlier transfer.
169 * Internally, libusb's synchronous interface is expressed in terms of function
170 * calls to the asynchronous interface.
172 * For details on how to use the asynchronous API, see the
173 * \ref asyncio "asynchronous I/O API" documentation pages.
177 * @defgroup asyncio Asynchronous device I/O
179 * This page details libusb's asynchronous (non-blocking) API for USB device
180 * I/O. This interface is very powerful but is also quite complex - you will
181 * need to read this page carefully to understand the necessary considerations
182 * and issues surrounding use of this interface. Simplistic applications
183 * may wish to consider the \ref syncio "synchronous I/O API" instead.
185 * The asynchronous interface is built around the idea of separating transfer
186 * submission and handling of transfer completion (the synchronous model
187 * combines both of these into one). There may be a long delay between
188 * submission and completion, however the asynchronous submission function
189 * is non-blocking so will return control to your application during that
190 * potentially long delay.
192 * \section asyncabstraction Transfer abstraction
194 * For the asynchronous I/O, libusb implements the concept of a generic
195 * transfer entity for all types of I/O (control, bulk, interrupt,
196 * isochronous). The generic transfer object must be treated slightly
197 * differently depending on which type of I/O you are performing with it.
199 * This is represented by the public libusb_transfer structure type.
201 * \section asynctrf Asynchronous transfers
203 * We can view asynchronous I/O as a 5 step process:
207 * -# Completion handling
210 * \subsection asyncalloc Allocation
212 * This step involves allocating memory for a USB transfer. This is the
213 * generic transfer object mentioned above. At this stage, the transfer
214 * is "blank" with no details about what type of I/O it will be used for.
216 * Allocation is done with the libusb_alloc_transfer() function. You must use
217 * this function rather than allocating your own transfers.
219 * \subsection asyncfill Filling
221 * This step is where you take a previously allocated transfer and fill it
222 * with information to determine the message type and direction, data buffer,
223 * callback function, etc.
225 * You can either fill the required fields yourself or you can use the
226 * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
227 * and libusb_fill_interrupt_transfer().
229 * \subsection asyncsubmit Submission
231 * When you have allocated a transfer and filled it, you can submit it using
232 * libusb_submit_transfer(). This function returns immediately but can be
233 * regarded as firing off the I/O request in the background.
235 * \subsection asynccomplete Completion handling
237 * After a transfer has been submitted, one of four things can happen to it:
239 * - The transfer completes (i.e. some data was transferred)
240 * - The transfer has a timeout and the timeout expires before all data is
242 * - The transfer fails due to an error
243 * - The transfer is cancelled
245 * Each of these will cause the user-specified transfer callback function to
246 * be invoked. It is up to the callback function to determine which of the
247 * above actually happened and to act accordingly.
249 * \subsection Deallocation
251 * When a transfer has completed (i.e. the callback function has been invoked),
252 * you are advised to free the transfer (unless you wish to resubmit it, see
253 * below). Transfers are deallocated with libusb_free_transfer().
255 * It is undefined behaviour to free a transfer which has not completed.
257 * \section asyncresubmit Resubmission
259 * You may be wondering why allocation, filling, and submission are all
260 * separated above where they could reasonably be combined into a single
263 * The reason for separation is to allow you to resubmit transfers without
264 * having to allocate new ones every time. This is especially useful for
265 * common situations dealing with interrupt endpoints - you allocate one
266 * transfer, fill and submit it, and when it returns with results you just
267 * resubmit it for the next interrupt.
269 * \section asynccancel Cancellation
271 * Another advantage of using the asynchronous interface is that you have
272 * the ability to cancel transfers which have not yet completed. This is
273 * done by calling the libusb_cancel_transfer() function.
275 * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
276 * cancellation actually completes, the transfer's callback function will
277 * be invoked, and the callback function should check the transfer status to
278 * determine that it was cancelled.
280 * Freeing the transfer after it has been cancelled but before cancellation
281 * has completed will result in undefined behaviour.
283 * \section asyncctrl Considerations for control transfers
285 * The <tt>libusb_transfer</tt> structure is generic and hence does not
286 * include specific fields for the control-specific setup packet structure.
288 * In order to perform a control transfer, you must place the 8-byte setup
289 * packet at the start of the data buffer. To simplify this, you could
290 * cast the buffer pointer to type struct libusb_control_setup, or you can
291 * use the helper function libusb_fill_control_setup().
293 * The wLength field placed in the setup packet must be the length you would
294 * expect to be sent in the setup packet: the length of the payload that
295 * follows (or the expected maximum number of bytes to receive). However,
296 * the length field of the libusb_transfer object must be the length of
297 * the data buffer - i.e. it should be wLength <em>plus</em> the size of
298 * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
300 * If you use the helper functions, this is simplified for you:
301 * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
302 * data you are sending/requesting.
303 * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
304 * request size as the wLength value (i.e. do not include the extra space you
305 * allocated for the control setup).
306 * -# If this is a host-to-device transfer, place the data to be transferred
307 * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
308 * -# Call libusb_fill_control_transfer() to associate the data buffer with
309 * the transfer (and to set the remaining details such as callback and timeout).
310 * - Note that there is no parameter to set the length field of the transfer.
311 * The length is automatically inferred from the wLength field of the setup
313 * -# Submit the transfer.
315 * Further considerations are needed when handling transfer completion in
316 * your callback function:
317 * - As you might expect, the setup packet will still be sitting at the start
318 * of the data buffer.
319 * - If this was a device-to-host transfer, the received data will be sitting
320 * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
321 * - The actual_length field of the transfer structure is relative to the
322 * wLength of the setup packet, rather than the size of the data buffer. So,
323 * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
324 * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
325 * transferred in entirity.
327 * To simplify parsing of setup packets and obtaining the data from the
328 * correct offset, you may wish to use the libusb_control_transfer_get_data()
329 * and libusb_control_transfer_get_setup() functions within your transfer
332 * \section asynciso Considerations for isochronous transfers
334 * As isochronous transfers are more complicated than transfers to
335 * non-isochronous endpoints.
337 * To perform I/O to an isochronous endpoint, allocate the transfer by calling
338 * libusb_alloc_transfer() with an appropriate number of isochronous packets.
340 * During filling, set \ref libusb_transfer::endpoint_type "endpoint_type" to
341 * \ref libusb_endpoint_type::LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS
342 * "LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS", and set
343 * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than
344 * or equal to the number of packets you requested during allocation.
345 * libusb_alloc_transfer() does not set either of these fields for you, given
346 * that you might not even use the transfer on an isochronous endpoint.
348 * Next, populate the length field for the first num_iso_packets entries in
349 * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section
350 * 5.6.3 of the USB2 specifications describe how the maximum isochronous
351 * packet length is determined by the endpoint descriptor. FIXME need a helper
352 * function to find this.
353 * FIXME, write a helper function to set the length for all iso packets in an
356 * For outgoing transfers, you'll obviously fill the buffer and populate the
357 * packet descriptors in hope that all the data gets transferred. For incoming
358 * transfers, you must ensure the buffer has sufficient capacity for
359 * the situation where all packets transfer the full amount of requested data.
361 * Completion handling requires some extra consideration. The
362 * \ref libusb_transfer::actual_length "actual_length" field of the transfer
363 * is meaningless and should not be examined; instead you must refer to the
364 * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of
365 * each individual packet.
367 * The \ref libusb_transfer::status "status" field of the transfer is also a
369 * - If the packets were submitted and the isochronous data microframes
370 * completed normally, status will have value
371 * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED
372 * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred
373 * delays are not counted as transfer errors; the transfer.status field may
374 * indicate COMPLETED even if some or all of the packets failed. Refer to
375 * the \ref libusb_iso_packet_descriptor::status "status" field of each
376 * individual packet to determine packet failures.
377 * - The status field will have value
378 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR
379 * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered.
380 * - Other transfer status codes occur with normal behaviour.
382 * The data for each packet will be found at an offset into the buffer that
383 * can be calculated as if each prior packet completed in full. FIXME write
384 * a helper function to determine this, and flesh this description out a bit
387 * \section asyncmem Memory caveats
389 * In most circumstances, it is not safe to use stack memory for transfer
390 * buffers. This is because the function that fired off the asynchronous
391 * transfer may return before libusb has finished using the buffer, and when
392 * the function returns it's stack gets destroyed. This is true for both
393 * host-to-device and device-to-host transfers.
395 * The only case in which it is safe to use stack memory is where you can
396 * guarantee that the function owning the stack space for the buffer does not
397 * return until after the transfer's callback function has completed. In every
398 * other case, you need to use heap memory instead.
400 * \section asyncflags Fine control
402 * Through using this asynchronous interface, you may find yourself repeating
403 * a few simple operations many times. You can apply a bitwise OR of certain
404 * flags to a transfer to simplify certain things:
405 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
406 * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
407 * less than the requested amount of data being marked with status
408 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
409 * (they would normally be regarded as COMPLETED)
410 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
411 * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
412 * buffer when freeing the transfer.
413 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
414 * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
415 * transfer after the transfer callback returns.
417 * \section asyncevent Event handling
419 * In accordance of the aim of being a lightweight library, libusb does not
420 * create threads internally. This means that libusb code does not execute
421 * at any time other than when your application is calling a libusb function.
422 * However, an asynchronous model requires that libusb perform work at various
423 * points in time - namely processing the results of previously-submitted
424 * transfers and invoking the user-supplied callback function.
426 * This gives rise to the libusb_handle_events() function which your
427 * application must call into when libusb has work do to. This gives libusb
428 * the opportunity to reap pending transfers, invoke callbacks, etc.
430 * The first issue to discuss here is how your application can figure out
431 * when libusb has work to do. In fact, there are two naive options which
432 * do not actually require your application to know this:
433 * -# Periodically call libusb_handle_events() in non-blocking mode at fixed
434 * short intervals from your main loop
435 * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated
438 * The first option is plainly not very nice, and will cause unnecessary
439 * CPU wakeups leading to increased power usage and decreased battery life.
440 * The second option is not very nice either, but may be the nicest option
441 * available to you if the "proper" approach can not be applied to your
442 * application (read on...).
444 * The recommended option is to integrate libusb with your application main
445 * event loop. libusb exposes a set of file descriptors which allow you to do
446 * this. Your main loop is probably already calling poll() or select() or a
447 * variant on a set of file descriptors for other event sources (e.g. keyboard
448 * button presses, mouse movements, network sockets, etc). You then add
449 * libusb's file descriptors to your poll()/select() calls, and when activity
450 * is detected on such descriptors you know it is time to call
451 * libusb_handle_events().
453 * There is one final event handling complication. libusb supports
454 * asynchronous transfers which time out after a specified time period, and
455 * this requires that libusb is called into at or after the timeout so that
456 * the timeout can be handled. So, in addition to considering libusb's file
457 * descriptors in your main event loop, you must also consider that libusb
458 * sometimes needs to be called into at fixed points in time even when there
459 * is no file descriptor activity.
461 * For the details on retrieving the set of file descriptors and determining
462 * the next timeout, see the \ref poll "polling and timing" API documentation.
466 * @defgroup poll Polling and timing
468 * This page documents libusb's functions for polling events and timing.
469 * These functions are only necessary for users of the
470 * \ref asyncio "asynchronous API". If you are only using the simpler
471 * \ref syncio "synchronous API" then you do not need to ever call these
474 * The justification for the functionality described here has already been
475 * discussed in the \ref asyncevent "event handling" section of the
476 * asynchronous API documentation. In summary, libusb does not create internal
477 * threads for event processing and hence relies on your application calling
478 * into libusb at certain points in time so that pending events can be handled.
479 * In order to know precisely when libusb needs to be called into, libusb
480 * offers you a set of pollable file descriptors and information about when
481 * the next timeout expires.
483 * If you are using the asynchronous I/O API, you must take one of the two
484 * following options, otherwise your I/O will not complete.
486 * \section pollsimple The simple option
488 * If your application revolves solely around libusb and does not need to
489 * handle other event sources, you can have a program structure as follows:
492 // find and open device
493 // maybe fire off some initial async I/O
495 while (user_has_not_requested_exit)
496 libusb_handle_events();
501 * With such a simple main loop, you do not have to worry about managing
502 * sets of file descriptors or handling timeouts. libusb_handle_events() will
503 * handle those details internally.
505 * \section pollmain The more advanced option
507 * In more advanced applications, you will already have a main loop which
508 * is monitoring other event sources: network sockets, X11 events, mouse
509 * movements, etc. Through exposing a set of file descriptors, libusb is
510 * designed to cleanly integrate into such main loops.
512 * In addition to polling file descriptors for the other event sources, you
513 * take a set of file descriptors from libusb and monitor those too. When you
514 * detect activity on libusb's file descriptors, you call
515 * libusb_handle_events_timeout() in non-blocking mode.
517 * You must also consider the fact that libusb sometimes has to handle events
518 * at certain known times which do not generate activity on file descriptors.
519 * Your main loop must also consider these times, modify it's poll()/select()
520 * timeout accordingly, and track time so that libusb_handle_events_timeout()
521 * is called in non-blocking mode when timeouts expire.
523 * In pseudo-code, you want something that looks like:
528 while (user has not requested application exit) {
529 libusb_get_next_timeout();
530 select(on libusb file descriptors plus any other event sources of interest,
531 using a timeout no larger than the value libusb just suggested)
532 if (select() indicated activity on libusb file descriptors)
533 libusb_handle_events_timeout(0);
534 if (time has elapsed to or beyond the libusb timeout)
535 libusb_handle_events_timeout(0);
541 * The set of file descriptors that libusb uses as event sources may change
542 * during the life of your application. Rather than having to repeatedly
543 * call libusb_get_pollfds(), you can set up notification functions for when
544 * the file descriptor set changes using libusb_set_pollfd_notifiers().
550 list_init(&flying_transfers);
553 fd_removed_cb = NULL;
556 static int calculate_timeout(struct usbi_transfer *transfer)
559 struct timespec current_time;
560 unsigned int timeout =
561 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
566 r = clock_gettime(CLOCK_MONOTONIC, ¤t_time);
568 usbi_err("failed to read monotonic clock, errno=%d", errno);
572 current_time.tv_sec += timeout / 1000;
573 current_time.tv_nsec += (timeout % 1000) * 1000000;
575 if (current_time.tv_nsec > 1000000000) {
576 current_time.tv_nsec -= 1000000000;
577 current_time.tv_sec++;
580 TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time);
584 static void add_to_flying_list(struct usbi_transfer *transfer)
586 struct usbi_transfer *cur;
587 struct timeval *timeout = &transfer->timeout;
589 /* if we have no other flying transfers, start the list with this one */
590 if (list_empty(&flying_transfers)) {
591 list_add(&transfer->list, &flying_transfers);
595 /* if we have infinite timeout, append to end of list */
596 if (!timerisset(timeout)) {
597 list_add_tail(&transfer->list, &flying_transfers);
601 /* otherwise, find appropriate place in list */
602 list_for_each_entry(cur, &flying_transfers, list) {
603 /* find first timeout that occurs after the transfer in question */
604 struct timeval *cur_tv = &cur->timeout;
606 if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
607 (cur_tv->tv_sec == timeout->tv_sec &&
608 cur_tv->tv_usec > timeout->tv_usec)) {
609 list_add_tail(&transfer->list, &cur->list);
614 /* otherwise we need to be inserted at the end */
615 list_add_tail(&transfer->list, &flying_transfers);
618 static int submit_transfer(struct usbi_transfer *itransfer)
620 int r = usbi_backend->submit_transfer(itransfer);
624 add_to_flying_list(itransfer);
629 * Allocate a libusb transfer with a specified number of isochronous packet
630 * descriptors. The returned transfer is pre-initialized for you. When the new
631 * transfer is no longer needed, it should be freed with
632 * libusb_free_transfer().
634 * Transfers intended for non-isochronous endpoints (e.g. control, bulk,
635 * interrupt) should specify an iso_packets count of zero.
637 * For transfers intended for isochronous endpoints, specify an appropriate
638 * number of packet descriptors to be allocated as part of the transfer.
639 * The returned transfer is not specially initialized for isochronous I/O;
640 * you are still required to set the
641 * \ref libusb_transfer::num_iso_packets "num_iso_packets" and
642 * \ref libusb_transfer::endpoint_type "endpoint_type" fields accordingly.
644 * It is safe to allocate a transfer with some isochronous packets and then
645 * use it on a non-isochronous endpoint. If you do this, ensure that at time
646 * of submission, num_iso_packets is 0 and that endpoint_type is set
649 * \param iso_packets number of isochronous packet descriptors to allocate
650 * \returns a newly allocated transfer, or NULL on error
652 API_EXPORTED struct libusb_transfer *libusb_alloc_transfer(int iso_packets)
654 size_t os_alloc_size = usbi_backend->transfer_priv_size
655 + (usbi_backend->add_iso_packet_size * iso_packets);
656 int alloc_size = sizeof(struct usbi_transfer)
657 + sizeof(struct libusb_transfer)
658 + (sizeof(struct libusb_iso_packet_descriptor) * iso_packets)
660 struct usbi_transfer *itransfer = malloc(alloc_size);
664 memset(itransfer, 0, alloc_size);
665 itransfer->num_iso_packets = iso_packets;
666 return __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
670 * Free a transfer structure. This should be called for all transfers
671 * allocated with libusb_alloc_transfer().
673 * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
674 * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
675 * non-NULL, this function will also free the transfer buffer using the
676 * standard system memory allocator (e.g. free()).
678 * It is legal to call this function with a NULL transfer. In this case,
679 * the function will simply return safely.
681 * \param transfer the transfer to free
683 API_EXPORTED void libusb_free_transfer(struct libusb_transfer *transfer)
685 struct usbi_transfer *itransfer;
689 if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
690 free(transfer->buffer);
692 itransfer = __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
697 * Submit a transfer. This function will fire off the USB transfer and then
698 * return immediately.
700 * It is undefined behaviour to submit a transfer that has already been
701 * submitted but has not yet completed.
703 * \param transfer the transfer to submit
704 * \returns 0 on success
705 * \returns negative on error
707 API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)
709 struct usbi_transfer *itransfer =
710 __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
713 itransfer->transferred = 0;
714 r = calculate_timeout(itransfer);
718 if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL) {
719 struct libusb_control_setup *setup =
720 (struct libusb_control_setup *) transfer->buffer;
722 usbi_dbg("RQT=%02x RQ=%02x VAL=%04x IDX=%04x length=%d",
723 setup->bmRequestType, setup->bRequest, setup->wValue, setup->wIndex,
726 setup->wValue = cpu_to_le16(setup->wValue);
727 setup->wIndex = cpu_to_le16(setup->wIndex);
728 setup->wLength = cpu_to_le16(setup->wLength);
731 return submit_transfer(itransfer);
735 * Asynchronously cancel a previously submitted transfer.
736 * It is undefined behaviour to call this function on a transfer that is
737 * already being cancelled or has already completed.
738 * This function returns immediately, but this does not indicate cancellation
739 * is complete. Your callback function will be invoked at some later time
740 * with a transfer status of
741 * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
742 * "LIBUSB_TRANSFER_CANCELLED."
744 * \param transfer the transfer to cancel
745 * \returns 0 on success
746 * \returns non-zero on error
748 API_EXPORTED int libusb_cancel_transfer(struct libusb_transfer *transfer)
750 struct usbi_transfer *itransfer =
751 __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
755 r = usbi_backend->cancel_transfer(itransfer);
757 usbi_err("cancel transfer failed error %d", r);
762 * Cancel a transfer and wait for cancellation completion without invoking
763 * the transfer callback. This function will block.
765 * It is undefined behaviour to call this function on a transfer that is
766 * already being cancelled or has already completed.
768 * \param transfer the transfer to cancel
769 * \returns 0 on success
770 * \returns non-zero on error
772 API_EXPORTED int libusb_cancel_transfer_sync(struct libusb_transfer *transfer)
774 struct usbi_transfer *itransfer =
775 __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
779 r = usbi_backend->cancel_transfer(itransfer);
781 usbi_err("cancel transfer failed error %d", r);
785 itransfer->flags |= USBI_TRANSFER_SYNC_CANCELLED;
786 while (itransfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
787 r = libusb_handle_events();
795 void usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
796 enum libusb_transfer_status status)
798 struct libusb_transfer *transfer =
799 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
802 list_del(&itransfer->list);
803 if (status == LIBUSB_TRANSFER_SILENT_COMPLETION)
806 if (status == LIBUSB_TRANSFER_COMPLETED
807 && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
808 int rqlen = transfer->length;
809 if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL)
810 rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
811 if (rqlen != itransfer->transferred) {
812 usbi_dbg("interpreting short transfer as error");
813 status = LIBUSB_TRANSFER_ERROR;
817 flags = transfer->flags;
818 transfer->status = status;
819 transfer->actual_length = itransfer->transferred;
820 if (transfer->callback)
821 transfer->callback(transfer);
822 /* transfer might have been freed by the above call, do not use from
824 if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
825 libusb_free_transfer(transfer);
828 void usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
830 /* if the URB is being cancelled synchronously, raise cancellation
831 * completion event by unsetting flag, and ensure that user callback does
834 if (transfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
835 transfer->flags &= ~USBI_TRANSFER_SYNC_CANCELLED;
836 usbi_dbg("detected sync. cancel");
837 usbi_handle_transfer_completion(transfer,
838 LIBUSB_TRANSFER_SILENT_COMPLETION);
842 /* if the URB was cancelled due to timeout, report timeout to the user */
843 if (transfer->flags & USBI_TRANSFER_TIMED_OUT) {
844 usbi_dbg("detected timeout cancellation");
845 usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
849 /* otherwise its a normal async cancel */
850 usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
853 static void handle_timeout(struct usbi_transfer *itransfer)
855 /* handling timeouts is tricky, as we may race with the kernel: we may
856 * detect a timeout racing with the condition that the urb has actually
857 * completed. we asynchronously cancel the URB and report timeout
858 * to the user when the URB cancellation completes (or not at all if the
859 * URB actually gets delivered as per this race) */
860 struct libusb_transfer *transfer =
861 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
864 itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
865 r = libusb_cancel_transfer(transfer);
867 usbi_warn("async cancel failed %d errno=%d", r, errno);
870 static int handle_timeouts(void)
872 struct timespec systime_ts;
873 struct timeval systime;
874 struct usbi_transfer *transfer;
877 if (list_empty(&flying_transfers))
880 /* get current time */
881 r = clock_gettime(CLOCK_MONOTONIC, &systime_ts);
885 TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
887 /* iterate through flying transfers list, finding all transfers that
888 * have expired timeouts */
889 list_for_each_entry(transfer, &flying_transfers, list) {
890 struct timeval *cur_tv = &transfer->timeout;
892 /* if we've reached transfers of infinite timeout, we're all done */
893 if (!timerisset(cur_tv))
896 /* ignore timeouts we've already handled */
897 if (transfer->flags & USBI_TRANSFER_TIMED_OUT)
900 /* if transfer has non-expired timeout, nothing more to do */
901 if ((cur_tv->tv_sec > systime.tv_sec) ||
902 (cur_tv->tv_sec == systime.tv_sec &&
903 cur_tv->tv_usec > systime.tv_usec))
906 /* otherwise, we've got an expired timeout to handle */
907 handle_timeout(transfer);
913 static int handle_events(struct timeval *tv)
917 fd_set readfds, writefds;
918 fd_set *_readfds = NULL;
919 fd_set *_writefds = NULL;
920 struct usbi_pollfd *ipollfd;
921 int have_readfds = 0;
922 int have_writefds = 0;
923 struct timeval select_timeout;
924 struct timeval timeout;
926 r = libusb_get_next_timeout(&timeout);
928 /* timeout already expired? */
929 if (!timerisset(&timeout))
930 return handle_timeouts();
932 /* choose the smallest of next URB timeout or user specified timeout */
933 if (timercmp(&timeout, tv, <))
934 select_timeout = timeout;
936 select_timeout = *tv;
938 select_timeout = *tv;
943 list_for_each_entry(ipollfd, &pollfds, list) {
944 struct libusb_pollfd *pollfd = &ipollfd->pollfd;
946 if (pollfd->events & POLLIN) {
948 FD_SET(fd, &readfds);
950 if (pollfd->events & POLLOUT) {
952 FD_SET(fd, &writefds);
961 _writefds = &writefds;
963 usbi_dbg("select() with timeout in %d.%06ds", select_timeout.tv_sec,
964 select_timeout.tv_usec);
965 r = select(maxfd + 1, _readfds, _writefds, NULL, &select_timeout);
966 usbi_dbg("select() returned %d with %d.%06ds remaining",
967 r, select_timeout.tv_sec, select_timeout.tv_usec);
969 *tv = select_timeout;
970 return handle_timeouts();
971 } else if (r == -1 && errno == EINTR) {
974 usbi_err("select failed %d err=%d\n", r, errno);
978 r = usbi_backend->handle_events(_readfds, _writefds);
982 /* FIXME check return value? */
983 return handle_timeouts();
987 * Handle any pending events.
989 * libusb determines "pending events" by checking if any timeouts have expired
990 * and by checking the set of file descriptors for activity.
992 * If a zero timeval is passed, this function will handle any already-pending
993 * events and then immediately return in non-blocking style.
995 * If a non-zero timeval is passed and no events are currently pending, this
996 * function will block waiting for events to handle up until the specified
997 * timeout. If an event arrives or a signal is raised, this function will
1000 * \param tv the maximum time to block waiting for events, or zero for
1002 * \returns 0 on success
1003 * \returns non-zero on error
1005 API_EXPORTED int libusb_handle_events_timeout(struct timeval *tv)
1007 return handle_events(tv);
1011 * Handle any pending events in blocking mode with a sensible timeout. This
1012 * timeout is currently hardcoded at 2 seconds but we may change this if we
1013 * decide other values are more sensible. For finer control over whether this
1014 * function is blocking or non-blocking, or the maximum timeout, use
1015 * libusb_handle_events_timeout() instead.
1017 * \returns 0 on success
1018 * \returns non-zero on error
1020 API_EXPORTED int libusb_handle_events(void)
1025 return handle_events(&tv);
1029 * Determine the next internal timeout that libusb needs to handle. You only
1030 * need to use this function if you are calling poll() or select() or similar
1031 * on libusb's file descriptors yourself - you do not need to use it if you
1032 * are calling libusb_handle_events() or a variant directly.
1034 * You should call this function in your main loop in order to determine how
1035 * long to wait for select() or poll() to return results. libusb needs to be
1036 * called into at this timeout, so you should use it as an upper bound on
1037 * your select() or poll() call.
1039 * When the timeout has expired, call into libusb_handle_events_timeout()
1040 * (perhaps in non-blocking mode) so that libusb can handle the timeout.
1042 * This function may return 0 (success) and an all-zero timeval. If this is
1043 * the case, it indicates that libusb has a timeout that has already expired
1044 * so you should call libusb_handle_events_timeout() or similar immediately.
1046 * \param tv output location for a relative time against the current
1047 * clock in which libusb must be called into in order to process timeout events
1048 * \returns 0 on success
1049 * \returns non-zero on error
1051 API_EXPORTED int libusb_get_next_timeout(struct timeval *tv)
1053 struct usbi_transfer *transfer;
1054 struct timespec cur_ts;
1055 struct timeval cur_tv;
1056 struct timeval *next_timeout;
1060 if (list_empty(&flying_transfers)) {
1061 usbi_dbg("no URBs, no timeout!");
1065 /* find next transfer which hasn't already been processed as timed out */
1066 list_for_each_entry(transfer, &flying_transfers, list) {
1067 if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) {
1074 usbi_dbg("all URBs have already been processed for timeouts");
1078 next_timeout = &transfer->timeout;
1080 /* no timeout for next transfer */
1081 if (!timerisset(next_timeout)) {
1082 usbi_dbg("no URBs with timeouts, no timeout!");
1086 r = clock_gettime(CLOCK_MONOTONIC, &cur_ts);
1088 usbi_err("failed to read monotonic clock, errno=%d", errno);
1091 TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
1093 if (timercmp(&cur_tv, next_timeout, >=)) {
1094 usbi_dbg("first timeout already expired");
1097 timersub(next_timeout, &cur_tv, tv);
1098 usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
1105 * Register notification functions for file descriptor additions/removals.
1106 * These functions will be invoked for every new or removed file descriptor
1107 * that libusb uses as an event source.
1109 * To remove notifiers, pass NULL values for the function pointers.
1111 * \param added_cb pointer to function for addition notifications
1112 * \param removed_cb pointer to function for removal notifications
1114 API_EXPORTED void libusb_set_pollfd_notifiers(libusb_pollfd_added_cb added_cb,
1115 libusb_pollfd_removed_cb removed_cb)
1117 fd_added_cb = added_cb;
1118 fd_removed_cb = removed_cb;
1121 int usbi_add_pollfd(int fd, short events)
1123 struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
1127 usbi_dbg("add fd %d events %d", fd, events);
1128 ipollfd->pollfd.fd = fd;
1129 ipollfd->pollfd.events = events;
1130 list_add(&ipollfd->list, &pollfds);
1133 fd_added_cb(fd, events);
1137 void usbi_remove_pollfd(int fd)
1139 struct usbi_pollfd *ipollfd;
1142 usbi_dbg("remove fd %d", fd);
1143 list_for_each_entry(ipollfd, &pollfds, list)
1144 if (ipollfd->pollfd.fd == fd) {
1150 usbi_err("couldn't find fd %d to remove", fd);
1154 list_del(&ipollfd->list);
1161 * Retrieve a list of file descriptors that should be polled by your main loop
1162 * as libusb event sources.
1164 * The returned list is NULL-terminated and should be freed with free() when
1165 * done. The actual list contents must not be touched.
1167 * \returns a NULL-terminated list of libusb_pollfd structures, or NULL on
1170 API_EXPORTED const struct libusb_pollfd **libusb_get_pollfds(void)
1172 struct libusb_pollfd **ret;
1173 struct usbi_pollfd *ipollfd;
1177 list_for_each_entry(ipollfd, &pollfds, list)
1180 ret = calloc(cnt + 1, sizeof(struct libusb_pollfd *));
1184 list_for_each_entry(ipollfd, &pollfds, list)
1185 ret[i++] = (struct libusb_pollfd *) ipollfd;
1188 return (const struct libusb_pollfd **) ret;