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
29 #include <sys/select.h>
36 /* this is a list of in-flight transfer handles, sorted by timeout expiration.
37 * URBs to timeout the soonest are placed at the beginning of the list, URBs
38 * that will time out later are placed after, and urbs with infinite timeout
39 * are always placed at the very end. */
40 static struct list_head flying_transfers;
41 static pthread_mutex_t flying_transfers_lock = PTHREAD_MUTEX_INITIALIZER;
43 /* list of poll fd's */
44 static struct list_head pollfds;
45 static pthread_mutex_t pollfds_lock = PTHREAD_MUTEX_INITIALIZER;
47 /* user callbacks for pollfd changes */
48 static libusb_pollfd_added_cb fd_added_cb = NULL;
49 static libusb_pollfd_removed_cb fd_removed_cb = NULL;
52 * \page io Synchronous and asynchronous device I/O
54 * \section intro Introduction
56 * If you're using libusb in your application, you're probably wanting to
57 * perform I/O with devices - you want to perform USB data transfers.
59 * libusb offers two separate interfaces for device I/O. This page aims to
60 * introduce the two in order to help you decide which one is more suitable
61 * for your application. You can also choose to use both interfaces in your
62 * application by considering each transfer on a case-by-case basis.
64 * Once you have read through the following discussion, you should consult the
65 * detailed API documentation pages for the details:
69 * \section theory Transfers at a logical level
71 * At a logical level, USB transfers typically happen in two parts. For
72 * example, when reading data from a endpoint:
73 * -# A request for data is sent to the device
74 * -# Some time later, the incoming data is received by the host
76 * or when writing data to an endpoint:
78 * -# The data is sent to the device
79 * -# Some time later, the host receives acknowledgement from the device that
80 * the data has been transferred.
82 * There may be an indefinite delay between the two steps. Consider a
83 * fictional USB input device with a button that the user can press. In order
84 * to determine when the button is pressed, you would likely submit a request
85 * to read data on a bulk or interrupt endpoint and wait for data to arrive.
86 * Data will arrive when the button is pressed by the user, which is
87 * potentially hours later.
89 * libusb offers both a synchronous and an asynchronous interface to performing
90 * USB transfers. The main difference is that the synchronous interface
91 * combines both steps indicated above into a single function call, whereas
92 * the asynchronous interface separates them.
94 * \section sync The synchronous interface
96 * The synchronous I/O interface allows you to perform a USB transfer with
97 * a single function call. When the function call returns, the transfer has
98 * completed and you can parse the results.
100 * If you have used the libusb-0.1 before, this I/O style will seem familar to
101 * you. libusb-0.1 only offered a synchronous interface.
103 * In our input device example, to read button presses you might write code
104 * in the following style:
106 unsigned char data[4];
108 int r = libusb_bulk_transfer(handle, EP_IN, data, sizeof(data), &actual_length, 0);
109 if (r == 0 && actual_length == sizeof(data)) {
110 // results of the transaction can now be found in the data buffer
111 // parse them here and report button press
117 * The main advantage of this model is simplicity: you did everything with
118 * a single simple function call.
120 * However, this interface has its limitations. Your application will sleep
121 * inside libusb_bulk_transfer() until the transaction has completed. If it
122 * takes the user 3 hours to press the button, your application will be
123 * sleeping for that long. Execution will be tied up inside the library -
124 * the entire thread will be useless for that duration.
126 * Another issue is that by tieing up the thread with that single transaction
127 * there is no possibility of performing I/O with multiple endpoints and/or
128 * multiple devices simultaneously, unless you resort to creating one thread
131 * Additionally, there is no opportunity to cancel the transfer after the
132 * request has been submitted.
134 * For details on how to use the synchronous API, see the
135 * \ref syncio "synchronous I/O API documentation" pages.
137 * \section async The asynchronous interface
139 * Asynchronous I/O is the most significant new feature in libusb-1.0.
140 * Although it is a more complex interface, it solves all the issues detailed
143 * Instead of providing which functions that block until the I/O has complete,
144 * libusb's asynchronous interface presents non-blocking functions which
145 * begin a transfer and then return immediately. Your application passes a
146 * callback function pointer to this non-blocking function, which libusb will
147 * call with the results of the transaction when it has completed.
149 * Transfers which have been submitted through the non-blocking functions
150 * can be cancelled with a separate function call.
152 * The non-blocking nature of this interface allows you to be simultaneously
153 * performing I/O to multiple endpoints on multiple devices, without having
156 * This added flexibility does come with some complications though:
157 * - In the interest of being a lightweight library, libusb does not create
158 * threads and can only operate when your application is calling into it. Your
159 * application must call into libusb from it's main loop when events are ready
160 * to be handled, or you must use some other scheme to allow libusb to
161 * undertake whatever work needs to be done.
162 * - libusb also needs to be called into at certain fixed points in time in
163 * order to accurately handle transfer timeouts.
164 * - Memory handling becomes more complex. You cannot use stack memory unless
165 * the function with that stack is guaranteed not to return until the transfer
166 * callback has finished executing.
167 * - You generally lose some linearity from your code flow because submitting
168 * the transfer request is done in a separate function from where the transfer
169 * results are handled. This becomes particularly obvious when you want to
170 * submit a second transfer based on the results of an earlier transfer.
172 * Internally, libusb's synchronous interface is expressed in terms of function
173 * calls to the asynchronous interface.
175 * For details on how to use the asynchronous API, see the
176 * \ref asyncio "asynchronous I/O API" documentation pages.
180 * @defgroup asyncio Asynchronous device I/O
182 * This page details libusb's asynchronous (non-blocking) API for USB device
183 * I/O. This interface is very powerful but is also quite complex - you will
184 * need to read this page carefully to understand the necessary considerations
185 * and issues surrounding use of this interface. Simplistic applications
186 * may wish to consider the \ref syncio "synchronous I/O API" instead.
188 * The asynchronous interface is built around the idea of separating transfer
189 * submission and handling of transfer completion (the synchronous model
190 * combines both of these into one). There may be a long delay between
191 * submission and completion, however the asynchronous submission function
192 * is non-blocking so will return control to your application during that
193 * potentially long delay.
195 * \section asyncabstraction Transfer abstraction
197 * For the asynchronous I/O, libusb implements the concept of a generic
198 * transfer entity for all types of I/O (control, bulk, interrupt,
199 * isochronous). The generic transfer object must be treated slightly
200 * differently depending on which type of I/O you are performing with it.
202 * This is represented by the public libusb_transfer structure type.
204 * \section asynctrf Asynchronous transfers
206 * We can view asynchronous I/O as a 5 step process:
210 * -# Completion handling
213 * \subsection asyncalloc Allocation
215 * This step involves allocating memory for a USB transfer. This is the
216 * generic transfer object mentioned above. At this stage, the transfer
217 * is "blank" with no details about what type of I/O it will be used for.
219 * Allocation is done with the libusb_alloc_transfer() function. You must use
220 * this function rather than allocating your own transfers.
222 * \subsection asyncfill Filling
224 * This step is where you take a previously allocated transfer and fill it
225 * with information to determine the message type and direction, data buffer,
226 * callback function, etc.
228 * You can either fill the required fields yourself or you can use the
229 * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
230 * and libusb_fill_interrupt_transfer().
232 * \subsection asyncsubmit Submission
234 * When you have allocated a transfer and filled it, you can submit it using
235 * libusb_submit_transfer(). This function returns immediately but can be
236 * regarded as firing off the I/O request in the background.
238 * \subsection asynccomplete Completion handling
240 * After a transfer has been submitted, one of four things can happen to it:
242 * - The transfer completes (i.e. some data was transferred)
243 * - The transfer has a timeout and the timeout expires before all data is
245 * - The transfer fails due to an error
246 * - The transfer is cancelled
248 * Each of these will cause the user-specified transfer callback function to
249 * be invoked. It is up to the callback function to determine which of the
250 * above actually happened and to act accordingly.
252 * \subsection Deallocation
254 * When a transfer has completed (i.e. the callback function has been invoked),
255 * you are advised to free the transfer (unless you wish to resubmit it, see
256 * below). Transfers are deallocated with libusb_free_transfer().
258 * It is undefined behaviour to free a transfer which has not completed.
260 * \section asyncresubmit Resubmission
262 * You may be wondering why allocation, filling, and submission are all
263 * separated above where they could reasonably be combined into a single
266 * The reason for separation is to allow you to resubmit transfers without
267 * having to allocate new ones every time. This is especially useful for
268 * common situations dealing with interrupt endpoints - you allocate one
269 * transfer, fill and submit it, and when it returns with results you just
270 * resubmit it for the next interrupt.
272 * \section asynccancel Cancellation
274 * Another advantage of using the asynchronous interface is that you have
275 * the ability to cancel transfers which have not yet completed. This is
276 * done by calling the libusb_cancel_transfer() function.
278 * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
279 * cancellation actually completes, the transfer's callback function will
280 * be invoked, and the callback function should check the transfer status to
281 * determine that it was cancelled.
283 * Freeing the transfer after it has been cancelled but before cancellation
284 * has completed will result in undefined behaviour.
286 * \section asyncctrl Considerations for control transfers
288 * The <tt>libusb_transfer</tt> structure is generic and hence does not
289 * include specific fields for the control-specific setup packet structure.
291 * In order to perform a control transfer, you must place the 8-byte setup
292 * packet at the start of the data buffer. To simplify this, you could
293 * cast the buffer pointer to type struct libusb_control_setup, or you can
294 * use the helper function libusb_fill_control_setup().
296 * The wLength field placed in the setup packet must be the length you would
297 * expect to be sent in the setup packet: the length of the payload that
298 * follows (or the expected maximum number of bytes to receive). However,
299 * the length field of the libusb_transfer object must be the length of
300 * the data buffer - i.e. it should be wLength <em>plus</em> the size of
301 * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
303 * If you use the helper functions, this is simplified for you:
304 * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
305 * data you are sending/requesting.
306 * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
307 * request size as the wLength value (i.e. do not include the extra space you
308 * allocated for the control setup).
309 * -# If this is a host-to-device transfer, place the data to be transferred
310 * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
311 * -# Call libusb_fill_control_transfer() to associate the data buffer with
312 * the transfer (and to set the remaining details such as callback and timeout).
313 * - Note that there is no parameter to set the length field of the transfer.
314 * The length is automatically inferred from the wLength field of the setup
316 * -# Submit the transfer.
318 * Further considerations are needed when handling transfer completion in
319 * your callback function:
320 * - As you might expect, the setup packet will still be sitting at the start
321 * of the data buffer.
322 * - If this was a device-to-host transfer, the received data will be sitting
323 * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
324 * - The actual_length field of the transfer structure is relative to the
325 * wLength of the setup packet, rather than the size of the data buffer. So,
326 * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
327 * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
328 * transferred in entirity.
330 * To simplify parsing of setup packets and obtaining the data from the
331 * correct offset, you may wish to use the libusb_control_transfer_get_data()
332 * and libusb_control_transfer_get_setup() functions within your transfer
335 * Even though control endpoints do not halt, a completed control transfer
336 * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control
337 * request was not supported.
339 * \section asyncintr Considerations for interrupt transfers
341 * All interrupt transfers are performed using the polling interval presented
342 * by the bInterval value of the endpoint descriptor.
344 * \section asynciso Considerations for isochronous transfers
346 * Isochronous transfers are more complicated than transfers to
347 * non-isochronous endpoints.
349 * To perform I/O to an isochronous endpoint, allocate the transfer by calling
350 * libusb_alloc_transfer() with an appropriate number of isochronous packets.
352 * During filling, set \ref libusb_transfer::type "type" to
353 * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
354 * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set
355 * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than
356 * or equal to the number of packets you requested during allocation.
357 * libusb_alloc_transfer() does not set either of these fields for you, given
358 * that you might not even use the transfer on an isochronous endpoint.
360 * Next, populate the length field for the first num_iso_packets entries in
361 * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section
362 * 5.6.3 of the USB2 specifications describe how the maximum isochronous
363 * packet length is determined by wMaxPacketSize field in the endpoint
364 * descriptor. Two functions can help you here:
366 * - libusb_get_max_packet_size() is an easy way to determine the max
367 * packet size for an endpoint.
368 * - libusb_set_iso_packet_lengths() assigns the same length to all packets
369 * within a transfer, which is usually what you want.
371 * For outgoing transfers, you'll obviously fill the buffer and populate the
372 * packet descriptors in hope that all the data gets transferred. For incoming
373 * transfers, you must ensure the buffer has sufficient capacity for
374 * the situation where all packets transfer the full amount of requested data.
376 * Completion handling requires some extra consideration. The
377 * \ref libusb_transfer::actual_length "actual_length" field of the transfer
378 * is meaningless and should not be examined; instead you must refer to the
379 * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of
380 * each individual packet.
382 * The \ref libusb_transfer::status "status" field of the transfer is also a
384 * - If the packets were submitted and the isochronous data microframes
385 * completed normally, status will have value
386 * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED
387 * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred
388 * delays are not counted as transfer errors; the transfer.status field may
389 * indicate COMPLETED even if some or all of the packets failed. Refer to
390 * the \ref libusb_iso_packet_descriptor::status "status" field of each
391 * individual packet to determine packet failures.
392 * - The status field will have value
393 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR
394 * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered.
395 * - Other transfer status codes occur with normal behaviour.
397 * The data for each packet will be found at an offset into the buffer that
398 * can be calculated as if each prior packet completed in full. The
399 * libusb_get_iso_packet_offset() and libusb_get_iso_packet_offset_simple()
400 * functions may help you here.
402 * \section asyncmem Memory caveats
404 * In most circumstances, it is not safe to use stack memory for transfer
405 * buffers. This is because the function that fired off the asynchronous
406 * transfer may return before libusb has finished using the buffer, and when
407 * the function returns it's stack gets destroyed. This is true for both
408 * host-to-device and device-to-host transfers.
410 * The only case in which it is safe to use stack memory is where you can
411 * guarantee that the function owning the stack space for the buffer does not
412 * return until after the transfer's callback function has completed. In every
413 * other case, you need to use heap memory instead.
415 * \section asyncflags Fine control
417 * Through using this asynchronous interface, you may find yourself repeating
418 * a few simple operations many times. You can apply a bitwise OR of certain
419 * flags to a transfer to simplify certain things:
420 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
421 * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
422 * less than the requested amount of data being marked with status
423 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
424 * (they would normally be regarded as COMPLETED)
425 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
426 * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
427 * buffer when freeing the transfer.
428 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
429 * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
430 * transfer after the transfer callback returns.
432 * \section asyncevent Event handling
434 * In accordance of the aim of being a lightweight library, libusb does not
435 * create threads internally. This means that libusb code does not execute
436 * at any time other than when your application is calling a libusb function.
437 * However, an asynchronous model requires that libusb perform work at various
438 * points in time - namely processing the results of previously-submitted
439 * transfers and invoking the user-supplied callback function.
441 * This gives rise to the libusb_handle_events() function which your
442 * application must call into when libusb has work do to. This gives libusb
443 * the opportunity to reap pending transfers, invoke callbacks, etc.
445 * The first issue to discuss here is how your application can figure out
446 * when libusb has work to do. In fact, there are two naive options which
447 * do not actually require your application to know this:
448 * -# Periodically call libusb_handle_events() in non-blocking mode at fixed
449 * short intervals from your main loop
450 * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated
453 * The first option is plainly not very nice, and will cause unnecessary
454 * CPU wakeups leading to increased power usage and decreased battery life.
455 * The second option is not very nice either, but may be the nicest option
456 * available to you if the "proper" approach can not be applied to your
457 * application (read on...).
459 * The recommended option is to integrate libusb with your application main
460 * event loop. libusb exposes a set of file descriptors which allow you to do
461 * this. Your main loop is probably already calling poll() or select() or a
462 * variant on a set of file descriptors for other event sources (e.g. keyboard
463 * button presses, mouse movements, network sockets, etc). You then add
464 * libusb's file descriptors to your poll()/select() calls, and when activity
465 * is detected on such descriptors you know it is time to call
466 * libusb_handle_events().
468 * There is one final event handling complication. libusb supports
469 * asynchronous transfers which time out after a specified time period, and
470 * this requires that libusb is called into at or after the timeout so that
471 * the timeout can be handled. So, in addition to considering libusb's file
472 * descriptors in your main event loop, you must also consider that libusb
473 * sometimes needs to be called into at fixed points in time even when there
474 * is no file descriptor activity.
476 * For the details on retrieving the set of file descriptors and determining
477 * the next timeout, see the \ref poll "polling and timing" API documentation.
481 * @defgroup poll Polling and timing
483 * This page documents libusb's functions for polling events and timing.
484 * These functions are only necessary for users of the
485 * \ref asyncio "asynchronous API". If you are only using the simpler
486 * \ref syncio "synchronous API" then you do not need to ever call these
489 * The justification for the functionality described here has already been
490 * discussed in the \ref asyncevent "event handling" section of the
491 * asynchronous API documentation. In summary, libusb does not create internal
492 * threads for event processing and hence relies on your application calling
493 * into libusb at certain points in time so that pending events can be handled.
494 * In order to know precisely when libusb needs to be called into, libusb
495 * offers you a set of pollable file descriptors and information about when
496 * the next timeout expires.
498 * If you are using the asynchronous I/O API, you must take one of the two
499 * following options, otherwise your I/O will not complete.
501 * \section pollsimple The simple option
503 * If your application revolves solely around libusb and does not need to
504 * handle other event sources, you can have a program structure as follows:
507 // find and open device
508 // maybe fire off some initial async I/O
510 while (user_has_not_requested_exit)
511 libusb_handle_events();
516 * With such a simple main loop, you do not have to worry about managing
517 * sets of file descriptors or handling timeouts. libusb_handle_events() will
518 * handle those details internally.
520 * \section pollmain The more advanced option
522 * In more advanced applications, you will already have a main loop which
523 * is monitoring other event sources: network sockets, X11 events, mouse
524 * movements, etc. Through exposing a set of file descriptors, libusb is
525 * designed to cleanly integrate into such main loops.
527 * In addition to polling file descriptors for the other event sources, you
528 * take a set of file descriptors from libusb and monitor those too. When you
529 * detect activity on libusb's file descriptors, you call
530 * libusb_handle_events_timeout() in non-blocking mode.
532 * You must also consider the fact that libusb sometimes has to handle events
533 * at certain known times which do not generate activity on file descriptors.
534 * Your main loop must also consider these times, modify it's poll()/select()
535 * timeout accordingly, and track time so that libusb_handle_events_timeout()
536 * is called in non-blocking mode when timeouts expire.
538 * In pseudo-code, you want something that looks like:
543 while (user has not requested application exit) {
544 libusb_get_next_timeout();
545 select(on libusb file descriptors plus any other event sources of interest,
546 using a timeout no larger than the value libusb just suggested)
547 if (select() indicated activity on libusb file descriptors)
548 libusb_handle_events_timeout(0);
549 if (time has elapsed to or beyond the libusb timeout)
550 libusb_handle_events_timeout(0);
556 * The set of file descriptors that libusb uses as event sources may change
557 * during the life of your application. Rather than having to repeatedly
558 * call libusb_get_pollfds(), you can set up notification functions for when
559 * the file descriptor set changes using libusb_set_pollfd_notifiers().
565 list_init(&flying_transfers);
568 fd_removed_cb = NULL;
571 static int calculate_timeout(struct usbi_transfer *transfer)
574 struct timespec current_time;
575 unsigned int timeout =
576 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
581 r = clock_gettime(CLOCK_MONOTONIC, ¤t_time);
583 usbi_err("failed to read monotonic clock, errno=%d", errno);
587 current_time.tv_sec += timeout / 1000;
588 current_time.tv_nsec += (timeout % 1000) * 1000000;
590 if (current_time.tv_nsec > 1000000000) {
591 current_time.tv_nsec -= 1000000000;
592 current_time.tv_sec++;
595 TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time);
599 static void add_to_flying_list(struct usbi_transfer *transfer)
601 struct usbi_transfer *cur;
602 struct timeval *timeout = &transfer->timeout;
604 pthread_mutex_lock(&flying_transfers_lock);
606 /* if we have no other flying transfers, start the list with this one */
607 if (list_empty(&flying_transfers)) {
608 list_add(&transfer->list, &flying_transfers);
612 /* if we have infinite timeout, append to end of list */
613 if (!timerisset(timeout)) {
614 list_add_tail(&transfer->list, &flying_transfers);
618 /* otherwise, find appropriate place in list */
619 list_for_each_entry(cur, &flying_transfers, list) {
620 /* find first timeout that occurs after the transfer in question */
621 struct timeval *cur_tv = &cur->timeout;
623 if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
624 (cur_tv->tv_sec == timeout->tv_sec &&
625 cur_tv->tv_usec > timeout->tv_usec)) {
626 list_add_tail(&transfer->list, &cur->list);
631 /* otherwise we need to be inserted at the end */
632 list_add_tail(&transfer->list, &flying_transfers);
634 pthread_mutex_unlock(&flying_transfers_lock);
638 * Allocate a libusb transfer with a specified number of isochronous packet
639 * descriptors. The returned transfer is pre-initialized for you. When the new
640 * transfer is no longer needed, it should be freed with
641 * libusb_free_transfer().
643 * Transfers intended for non-isochronous endpoints (e.g. control, bulk,
644 * interrupt) should specify an iso_packets count of zero.
646 * For transfers intended for isochronous endpoints, specify an appropriate
647 * number of packet descriptors to be allocated as part of the transfer.
648 * The returned transfer is not specially initialized for isochronous I/O;
649 * you are still required to set the
650 * \ref libusb_transfer::num_iso_packets "num_iso_packets" and
651 * \ref libusb_transfer::type "type" fields accordingly.
653 * It is safe to allocate a transfer with some isochronous packets and then
654 * use it on a non-isochronous endpoint. If you do this, ensure that at time
655 * of submission, num_iso_packets is 0 and that type is set appropriately.
657 * \param iso_packets number of isochronous packet descriptors to allocate
658 * \returns a newly allocated transfer, or NULL on error
660 API_EXPORTED struct libusb_transfer *libusb_alloc_transfer(int iso_packets)
662 size_t os_alloc_size = usbi_backend->transfer_priv_size
663 + (usbi_backend->add_iso_packet_size * iso_packets);
664 int alloc_size = sizeof(struct usbi_transfer)
665 + sizeof(struct libusb_transfer)
666 + (sizeof(struct libusb_iso_packet_descriptor) * iso_packets)
668 struct usbi_transfer *itransfer = malloc(alloc_size);
672 memset(itransfer, 0, alloc_size);
673 itransfer->num_iso_packets = iso_packets;
674 return __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
678 * Free a transfer structure. This should be called for all transfers
679 * allocated with libusb_alloc_transfer().
681 * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
682 * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
683 * non-NULL, this function will also free the transfer buffer using the
684 * standard system memory allocator (e.g. free()).
686 * It is legal to call this function with a NULL transfer. In this case,
687 * the function will simply return safely.
689 * \param transfer the transfer to free
691 API_EXPORTED void libusb_free_transfer(struct libusb_transfer *transfer)
693 struct usbi_transfer *itransfer;
697 if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
698 free(transfer->buffer);
700 itransfer = __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
705 * Submit a transfer. This function will fire off the USB transfer and then
706 * return immediately.
708 * It is undefined behaviour to submit a transfer that has already been
709 * submitted but has not yet completed.
711 * \param transfer the transfer to submit
712 * \returns 0 on success, or a LIBUSB_ERROR code on failure
714 API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)
716 struct usbi_transfer *itransfer =
717 __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
720 itransfer->transferred = 0;
721 r = calculate_timeout(itransfer);
723 return LIBUSB_ERROR_OTHER;
725 if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL) {
726 struct libusb_control_setup *setup =
727 (struct libusb_control_setup *) transfer->buffer;
729 usbi_dbg("RQT=%02x RQ=%02x VAL=%04x IDX=%04x length=%d",
730 setup->bmRequestType, setup->bRequest, setup->wValue, setup->wIndex,
733 setup->wValue = cpu_to_le16(setup->wValue);
734 setup->wIndex = cpu_to_le16(setup->wIndex);
735 setup->wLength = cpu_to_le16(setup->wLength);
738 add_to_flying_list(itransfer);
739 r = usbi_backend->submit_transfer(itransfer);
741 pthread_mutex_lock(&flying_transfers_lock);
742 list_del(&itransfer->list);
743 pthread_mutex_unlock(&flying_transfers_lock);
750 * Asynchronously cancel a previously submitted transfer.
751 * It is undefined behaviour to call this function on a transfer that is
752 * already being cancelled or has already completed.
753 * This function returns immediately, but this does not indicate cancellation
754 * is complete. Your callback function will be invoked at some later time
755 * with a transfer status of
756 * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
757 * "LIBUSB_TRANSFER_CANCELLED."
759 * \param transfer the transfer to cancel
760 * \returns 0 on success
761 * \returns non-zero on error
763 API_EXPORTED int libusb_cancel_transfer(struct libusb_transfer *transfer)
765 struct usbi_transfer *itransfer =
766 __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
770 r = usbi_backend->cancel_transfer(itransfer);
772 usbi_err("cancel transfer failed error %d", r);
776 void usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
777 enum libusb_transfer_status status)
779 struct libusb_transfer *transfer =
780 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
783 pthread_mutex_lock(&flying_transfers_lock);
784 list_del(&itransfer->list);
785 pthread_mutex_unlock(&flying_transfers_lock);
787 if (status == LIBUSB_TRANSFER_COMPLETED
788 && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
789 int rqlen = transfer->length;
790 if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL)
791 rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
792 if (rqlen != itransfer->transferred) {
793 usbi_dbg("interpreting short transfer as error");
794 status = LIBUSB_TRANSFER_ERROR;
798 flags = transfer->flags;
799 transfer->status = status;
800 transfer->actual_length = itransfer->transferred;
801 if (transfer->callback)
802 transfer->callback(transfer);
803 /* transfer might have been freed by the above call, do not use from
805 if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
806 libusb_free_transfer(transfer);
809 void usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
811 /* if the URB was cancelled due to timeout, report timeout to the user */
812 if (transfer->flags & USBI_TRANSFER_TIMED_OUT) {
813 usbi_dbg("detected timeout cancellation");
814 usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
818 /* otherwise its a normal async cancel */
819 usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
822 static void handle_timeout(struct usbi_transfer *itransfer)
824 struct libusb_transfer *transfer =
825 __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
828 itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
829 r = libusb_cancel_transfer(transfer);
831 usbi_warn("async cancel failed %d errno=%d", r, errno);
834 static int handle_timeouts(void)
836 struct timespec systime_ts;
837 struct timeval systime;
838 struct usbi_transfer *transfer;
841 pthread_mutex_lock(&flying_transfers_lock);
842 if (list_empty(&flying_transfers))
845 /* get current time */
846 r = clock_gettime(CLOCK_MONOTONIC, &systime_ts);
850 TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
852 /* iterate through flying transfers list, finding all transfers that
853 * have expired timeouts */
854 list_for_each_entry(transfer, &flying_transfers, list) {
855 struct timeval *cur_tv = &transfer->timeout;
857 /* if we've reached transfers of infinite timeout, we're all done */
858 if (!timerisset(cur_tv))
861 /* ignore timeouts we've already handled */
862 if (transfer->flags & USBI_TRANSFER_TIMED_OUT)
865 /* if transfer has non-expired timeout, nothing more to do */
866 if ((cur_tv->tv_sec > systime.tv_sec) ||
867 (cur_tv->tv_sec == systime.tv_sec &&
868 cur_tv->tv_usec > systime.tv_usec))
871 /* otherwise, we've got an expired timeout to handle */
872 handle_timeout(transfer);
876 pthread_mutex_unlock(&flying_transfers_lock);
880 static int handle_events(struct timeval *tv)
884 fd_set readfds, writefds;
885 fd_set *_readfds = NULL;
886 fd_set *_writefds = NULL;
887 struct usbi_pollfd *ipollfd;
888 int have_readfds = 0;
889 int have_writefds = 0;
890 struct timeval select_timeout;
891 struct timeval timeout;
893 r = libusb_get_next_timeout(&timeout);
895 /* timeout already expired? */
896 if (!timerisset(&timeout))
897 return handle_timeouts();
899 /* choose the smallest of next URB timeout or user specified timeout */
900 if (timercmp(&timeout, tv, <))
901 select_timeout = timeout;
903 select_timeout = *tv;
905 select_timeout = *tv;
910 pthread_mutex_lock(&pollfds_lock);
911 list_for_each_entry(ipollfd, &pollfds, list) {
912 struct libusb_pollfd *pollfd = &ipollfd->pollfd;
914 if (pollfd->events & POLLIN) {
916 FD_SET(fd, &readfds);
918 if (pollfd->events & POLLOUT) {
920 FD_SET(fd, &writefds);
925 pthread_mutex_unlock(&pollfds_lock);
930 _writefds = &writefds;
932 usbi_dbg("select() with timeout in %d.%06ds", select_timeout.tv_sec,
933 select_timeout.tv_usec);
934 r = select(maxfd + 1, _readfds, _writefds, NULL, &select_timeout);
935 usbi_dbg("select() returned %d with %d.%06ds remaining",
936 r, select_timeout.tv_sec, select_timeout.tv_usec);
938 *tv = select_timeout;
939 return handle_timeouts();
940 } else if (r == -1 && errno == EINTR) {
943 usbi_err("select failed %d err=%d\n", r, errno);
944 return LIBUSB_ERROR_IO;
947 r = usbi_backend->handle_events(_readfds, _writefds);
949 usbi_err("backend handle_events failed with error %d", r);
955 * Handle any pending events.
957 * libusb determines "pending events" by checking if any timeouts have expired
958 * and by checking the set of file descriptors for activity.
960 * If a zero timeval is passed, this function will handle any already-pending
961 * events and then immediately return in non-blocking style.
963 * If a non-zero timeval is passed and no events are currently pending, this
964 * function will block waiting for events to handle up until the specified
965 * timeout. If an event arrives or a signal is raised, this function will
968 * \param tv the maximum time to block waiting for events, or zero for
970 * \returns 0 on success, or a LIBUSB_ERROR code on failure
972 API_EXPORTED int libusb_handle_events_timeout(struct timeval *tv)
974 return handle_events(tv);
978 * Handle any pending events in blocking mode with a sensible timeout. This
979 * timeout is currently hardcoded at 2 seconds but we may change this if we
980 * decide other values are more sensible. For finer control over whether this
981 * function is blocking or non-blocking, or the maximum timeout, use
982 * libusb_handle_events_timeout() instead.
984 * \returns 0 on success, or a LIBUSB_ERROR code on failure
986 API_EXPORTED int libusb_handle_events(void)
991 return handle_events(&tv);
995 * Determine the next internal timeout that libusb needs to handle. You only
996 * need to use this function if you are calling poll() or select() or similar
997 * on libusb's file descriptors yourself - you do not need to use it if you
998 * are calling libusb_handle_events() or a variant directly.
1000 * You should call this function in your main loop in order to determine how
1001 * long to wait for select() or poll() to return results. libusb needs to be
1002 * called into at this timeout, so you should use it as an upper bound on
1003 * your select() or poll() call.
1005 * When the timeout has expired, call into libusb_handle_events_timeout()
1006 * (perhaps in non-blocking mode) so that libusb can handle the timeout.
1008 * This function may return 1 (success) and an all-zero timeval. If this is
1009 * the case, it indicates that libusb has a timeout that has already expired
1010 * so you should call libusb_handle_events_timeout() or similar immediately.
1011 * A return code of 0 indicates that there are no pending timeouts.
1013 * \param tv output location for a relative time against the current
1014 * clock in which libusb must be called into in order to process timeout events
1015 * \returns 0 if there are no pending timeouts, 1 if a timeout was returned,
1016 * or LIBUSB_ERROR_OTHER on failure
1018 API_EXPORTED int libusb_get_next_timeout(struct timeval *tv)
1020 struct usbi_transfer *transfer;
1021 struct timespec cur_ts;
1022 struct timeval cur_tv;
1023 struct timeval *next_timeout;
1027 pthread_mutex_lock(&flying_transfers_lock);
1028 if (list_empty(&flying_transfers)) {
1029 pthread_mutex_unlock(&flying_transfers_lock);
1030 usbi_dbg("no URBs, no timeout!");
1034 /* find next transfer which hasn't already been processed as timed out */
1035 list_for_each_entry(transfer, &flying_transfers, list) {
1036 if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) {
1041 pthread_mutex_unlock(&flying_transfers_lock);
1044 usbi_dbg("all URBs have already been processed for timeouts");
1048 next_timeout = &transfer->timeout;
1050 /* no timeout for next transfer */
1051 if (!timerisset(next_timeout)) {
1052 usbi_dbg("no URBs with timeouts, no timeout!");
1056 r = clock_gettime(CLOCK_MONOTONIC, &cur_ts);
1058 usbi_err("failed to read monotonic clock, errno=%d", errno);
1059 return LIBUSB_ERROR_OTHER;
1061 TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
1063 if (timercmp(&cur_tv, next_timeout, >=)) {
1064 usbi_dbg("first timeout already expired");
1067 timersub(next_timeout, &cur_tv, tv);
1068 usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
1075 * Register notification functions for file descriptor additions/removals.
1076 * These functions will be invoked for every new or removed file descriptor
1077 * that libusb uses as an event source.
1079 * To remove notifiers, pass NULL values for the function pointers.
1081 * \param added_cb pointer to function for addition notifications
1082 * \param removed_cb pointer to function for removal notifications
1084 API_EXPORTED void libusb_set_pollfd_notifiers(libusb_pollfd_added_cb added_cb,
1085 libusb_pollfd_removed_cb removed_cb)
1087 fd_added_cb = added_cb;
1088 fd_removed_cb = removed_cb;
1091 int usbi_add_pollfd(int fd, short events)
1093 struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
1097 usbi_dbg("add fd %d events %d", fd, events);
1098 ipollfd->pollfd.fd = fd;
1099 ipollfd->pollfd.events = events;
1100 pthread_mutex_lock(&pollfds_lock);
1101 list_add(&ipollfd->list, &pollfds);
1102 pthread_mutex_unlock(&pollfds_lock);
1105 fd_added_cb(fd, events);
1109 void usbi_remove_pollfd(int fd)
1111 struct usbi_pollfd *ipollfd;
1114 usbi_dbg("remove fd %d", fd);
1115 pthread_mutex_lock(&pollfds_lock);
1116 list_for_each_entry(ipollfd, &pollfds, list)
1117 if (ipollfd->pollfd.fd == fd) {
1123 usbi_err("couldn't find fd %d to remove", fd);
1124 pthread_mutex_unlock(&pollfds_lock);
1128 list_del(&ipollfd->list);
1129 pthread_mutex_unlock(&pollfds_lock);
1136 * Retrieve a list of file descriptors that should be polled by your main loop
1137 * as libusb event sources.
1139 * The returned list is NULL-terminated and should be freed with free() when
1140 * done. The actual list contents must not be touched.
1142 * \returns a NULL-terminated list of libusb_pollfd structures, or NULL on
1145 API_EXPORTED const struct libusb_pollfd **libusb_get_pollfds(void)
1147 struct libusb_pollfd **ret = NULL;
1148 struct usbi_pollfd *ipollfd;
1152 pthread_mutex_lock(&pollfds_lock);
1153 list_for_each_entry(ipollfd, &pollfds, list)
1156 ret = calloc(cnt + 1, sizeof(struct libusb_pollfd *));
1160 list_for_each_entry(ipollfd, &pollfds, list)
1161 ret[i++] = (struct libusb_pollfd *) ipollfd;
1165 pthread_mutex_unlock(&pollfds_lock);
1166 return (const struct libusb_pollfd **) ret;