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 #define TRANSFER_TO_PRIV(trf) (container_of((trf), struct usbi_transfer, pub))
37 /* this is a list of in-flight rb_handles, sorted by timeout expiration.
38 * URBs to timeout the soonest are placed at the beginning of the list, URBs
39 * that will time out later are placed after, and urbs with infinite timeout
40 * are always placed at the very end. */
41 static struct list_head flying_transfers;
43 /* list of poll fd's */
44 static struct list_head pollfds;
46 /* user callbacks for pollfd changes */
47 static libusb_pollfd_added_cb fd_added_cb = NULL;
48 static libusb_pollfd_removed_cb fd_removed_cb = NULL;
51 * \page io Synchronous and asynchronous device I/O
53 * \section intro Introduction
55 * If you're using libusb in your application, you're probably wanting to
56 * perform I/O with devices - you want to perform USB data transfers.
58 * libusb offers two separate interfaces for device I/O. This page aims to
59 * introduce the two in order to help you decide which one is more suitable
60 * for your application. You can also choose to use both interfaces in your
61 * application by considering each transfer on a case-by-case basis.
63 * Once you have read through the following discussion, you should consult the
64 * detailed API documentation pages for the details:
68 * \section theory Transfers at a logical level
70 * At a logical level, USB transfers typically happen in two parts. For
71 * example, when reading data from a endpoint:
72 * -# A request for data is sent to the device
73 * -# Some time later, the incoming data is received by the host
75 * or when writing data to an endpoint:
77 * -# The data is sent to the device
78 * -# Some time later, the host receives acknowledgement from the device that
79 * the data has been transferred.
81 * There may be an indefinite delay between the two steps. Consider a
82 * fictional USB input device with a button that the user can press. In order
83 * to determine when the button is pressed, you would likely submit a request
84 * to read data on a bulk or interrupt endpoint and wait for data to arrive.
85 * Data will arrive when the button is pressed by the user, which is
86 * potentially hours later.
88 * libusb offers both a synchronous and an asynchronous interface to performing
89 * USB transfers. The main difference is that the synchronous interface
90 * combines both steps indicated above into a single function call, whereas
91 * the asynchronous interface separates them.
93 * \section sync The synchronous interface
95 * The synchronous I/O interface allows you to perform a USB transfer with
96 * a single function call. When the function call returns, the transfer has
97 * completed and you can parse the results.
99 * If you have used the libusb-0.1 before, this I/O style will seem familar to
100 * you. libusb-0.1 only offered a synchronous interface.
102 * In our input device example, to read button presses you might write code
103 * in the following style:
105 unsigned char data[4];
107 int r = libusb_bulk_transfer(handle, EP_IN, data, sizeof(data), &actual_length, 0);
108 if (r == 0 && actual_length == sizeof(data)) {
109 // results of the transaction can now be found in the data buffer
110 // parse them here and report button press
116 * The main advantage of this model is simplicity: you did everything with
117 * a single simple function call.
119 * However, this interface has its limitations. Your application will sleep
120 * inside libusb_bulk_transfer() until the transaction has completed. If it
121 * takes the user 3 hours to press the button, your application will be
122 * sleeping for that long. Execution will be tied up inside the library -
123 * the entire thread will be useless for that duration.
125 * Another issue is that by tieing up the thread with that single transaction
126 * there is no possibility of performing I/O with multiple endpoints and/or
127 * multiple devices simultaneously, unless you resort to creating one thread
130 * Additionally, there is no opportunity to cancel the transfer after the
131 * request has been submitted.
133 * For details on how to use the synchronous API, see the
134 * \ref syncio "synchronous I/O API documentation" pages.
136 * \section async The asynchronous interface
138 * Asynchronous I/O is the most significant new feature in libusb-1.0.
139 * Although it is a more complex interface, it solves all the issues detailed
142 * Instead of providing which functions that block until the I/O has complete,
143 * libusb's asynchronous interface presents non-blocking functions which
144 * begin a transfer and then return immediately. Your application passes a
145 * callback function pointer to this non-blocking function, which libusb will
146 * call with the results of the transaction when it has completed.
148 * Transfers which have been submitted through the non-blocking functions
149 * can be cancelled with a separate function call.
151 * The non-blocking nature of this interface allows you to be simultaneously
152 * performing I/O to multiple endpoints on multiple devices, without having
155 * This added flexibility does come with some complications though:
156 * - In the interest of being a lightweight library, libusb does not create
157 * threads and can only operate when your application is calling into it. Your
158 * application must call into libusb from it's main loop when events are ready
159 * to be handled, or you must use some other scheme to allow libusb to
160 * undertake whatever work needs to be done.
161 * - libusb also needs to be called into at certain fixed points in time in
162 * order to accurately handle transfer timeouts.
163 * - Memory handling becomes more complex. You cannot use stack memory unless
164 * the function with that stack is guaranteed not to return until the transfer
165 * callback has finished executing.
166 * - You generally lose some linearity from your code flow because submitting
167 * the transfer request is done in a separate function from where the transfer
168 * results are handled. This becomes particularly obvious when you want to
169 * submit a second transfer based on the results of an earlier transfer.
171 * Internally, libusb's synchronous interface is expressed in terms of function
172 * calls to the asynchronous interface.
174 * For details on how to use the asynchronous API, see the
175 * \ref asyncio "asynchronous I/O API" documentation pages.
179 * @defgroup asyncio Asynchronous device I/O
181 * This page details libusb's asynchronous (non-blocking) API for USB device
182 * I/O. This interface is very powerful but is also quite complex - you will
183 * need to read this page carefully to understand the necessary considerations
184 * and issues surrounding use of this interface. Simplistic applications
185 * may wish to consider the \ref syncio "synchronous I/O API" instead.
187 * The asynchronous interface is built around the idea of separating transfer
188 * submission and handling of transfer completion (the synchronous model
189 * combines both of these into one). There may be a long delay between
190 * submission and completion, however the asynchronous submission function
191 * is non-blocking so will return control to your application during that
192 * potentially long delay.
194 * \section asyncabstraction Transfer abstraction
196 * For the asynchronous I/O, libusb implements the concept of a generic
197 * transfer entity for all types of I/O (control, bulk, interrupt,
198 * isochronous). The generic transfer object must be treated slightly
199 * differently depending on which type of I/O you are performing with it.
201 * This is represented by the public libusb_transfer structure type.
203 * \section asynctrf Asynchronous transfers
205 * We can view asynchronous I/O as a 5 step process:
209 * -# Completion handling
212 * \subsection asyncalloc Allocation
214 * This step involves allocating memory for a USB transfer. This is the
215 * generic transfer object mentioned above. At this stage, the transfer
216 * is "blank" with no details about what type of I/O it will be used for.
218 * Allocation is done with the libusb_alloc_transfer() function. It is also
219 * possible to allocate your own libusb_transfer structure, but only if you
220 * take the following into account:
221 * -# For implementation reasons, the memory allocated for the transfer must
222 * actually be larger than sizeof(struct libusb_transfer). If you wish to
223 * allocate your own transfers, you must allocate them with the size
224 * determined by libusb_get_transfer_alloc_size().
225 * -# After allocating space for a transfer, you must initialize it with
226 * libusb_init_transfer().
228 * \subsection asyncfill Filling
230 * This step is where you take a previously allocated transfer and fill it
231 * with information to determine the message type and direction, data buffer,
232 * callback function, etc.
234 * You can either fill the required fields yourself or you can use the
235 * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
236 * and libusb_fill_interrupt_transfer().
238 * \subsection asyncsubmit Submission
240 * When you have allocated a transfer and filled it, you can submit it using
241 * libusb_submit_transfer(). This function returns immediately but can be
242 * regarded as firing off the I/O request in the background.
244 * \subsection asynccomplete Completion handling
246 * After a transfer has been submitted, one of four things can happen to it:
248 * - The transfer completes (i.e. some data was transferred)
249 * - The transfer has a timeout and the timeout expires before all data is
251 * - The transfer fails due to an error
252 * - The transfer is cancelled
254 * Each of these will cause the user-specified transfer callback function to
255 * be invoked. It is up to the callback function to determine which of the
256 * above actually happened and to act accordingly.
258 * \subsection Deallocation
260 * When a transfer has completed (i.e. the callback function has been invoked),
261 * you are advised to free the transfer (unless you wish to resubmit it, see
264 * If you allocated the transfer with libusb_alloc_transfer(), deallocate it
265 * with libusb_free_transfer(). If you're using your own memory management
266 * scheme, free it through your scheme.
268 * It is undefined behaviour to free a transfer which has not completed.
270 * \section asyncresubmit Resubmission
272 * You may be wondering why allocation, filling, and submission are all
273 * separated above where they could reasonably be combined into a single
276 * The reason for separation is to allow you to resubmit transfers without
277 * having to allocate new ones every time. This is especially useful for
278 * common situations dealing with interrupt endpoints - you allocate one
279 * transfer, fill and submit it, and when it returns with results you just
280 * resubmit it for the next interrupt.
282 * \section asynccancel Cancellation
284 * Another advantage of using the asynchronous interface is that you have
285 * the ability to cancel transfers which have not yet completed. This is
286 * done by calling the libusb_cancel_transfer() function.
288 * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
289 * cancellation actually completes, the transfer's callback function will
290 * be invoked, and the callback function should check the transfer status to
291 * determine that it was cancelled.
293 * Freeing the transfer after it has been cancelled but before cancellation
294 * has completed will result in undefined behaviour.
296 * \section asyncctrl Considerations for control transfers
298 * The <tt>libusb_transfer</tt> structure is generic and hence does not
299 * include specific fields for the control-specific setup packet structure.
301 * In order to perform a control transfer, you must place the 8-byte setup
302 * packet at the start of the data buffer. To simplify this, you could
303 * cast the buffer pointer to type struct libusb_control_setup, or you can
304 * use the helper function libusb_fill_control_setup().
306 * The wLength field placed in the setup packet must be the length you would
307 * expect to be sent in the setup packet: the length of the payload that
308 * follows (or the expected maximum number of bytes to receive). However,
309 * the length field of the libusb_transfer object must be the length of
310 * the data buffer - i.e. it should be wLength <em>plus</em> the size of
311 * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
313 * If you use the helper functions, this is simplified for you:
314 * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
315 * data you are sending/requesting.
316 * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
317 * request size as the wLength value (i.e. do not include the extra space you
318 * allocated for the control setup).
319 * -# If this is a host-to-device transfer, place the data to be transferred
320 * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
321 * -# Call libusb_fill_control_transfer() to associate the data buffer with
322 * the transfer (and to set the remaining details such as callback and timeout).
323 * - Note that there is no parameter to set the length field of the transfer.
324 * The length is automatically inferred from the wLength field of the setup
326 * -# Submit the transfer.
328 * Further considerations are needed when handling transfer completion in
329 * your callback function:
330 * - As you might expect, the setup packet will still be sitting at the start
331 * of the data buffer.
332 * - If this was a device-to-host transfer, the received data will be sitting
333 * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
334 * - The actual_length field of the transfer structure is relative to the
335 * wLength of the setup packet, rather than the size of the data buffer. So,
336 * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
337 * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
338 * transferred in entirity.
340 * To simplify parsing of setup packets and obtaining the data from the
341 * correct offset, you may wish to use the libusb_control_transfer_get_data()
342 * and libusb_control_transfer_get_setup() functions within your transfer
345 * \section asyncmem Memory caveats
347 * In most circumstances, it is not safe to use stack memory for transfer
348 * buffers. This is because the function that fired off the asynchronous
349 * transfer may return before libusb has finished using the buffer, and when
350 * the function returns it's stack gets destroyed. This is true for both
351 * host-to-device and device-to-host transfers.
353 * The only case in which it is safe to use stack memory is where you can
354 * guarantee that the function owning the stack space for the buffer does not
355 * return until after the transfer's callback function has completed. In every
356 * other case, you need to use heap memory instead.
358 * \section asyncflags Fine control
360 * Through using this asynchronous interface, you may find yourself repeating
361 * a few simple operations many times. You can apply a bitwise OR of certain
362 * flags to a transfer to simplify certain things:
363 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
364 * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
365 * less than the requested amount of data being marked with status
366 * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
367 * (they would normally be regarded as COMPLETED)
368 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
369 * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
370 * buffer when freeing the transfer.
371 * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
372 * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
373 * transfer after the transfer callback returns.
375 * \section asyncevent Event handling
377 * In accordance of the aim of being a lightweight library, libusb does not
378 * create threads internally. This means that libusb code does not execute
379 * at any time other than when your application is calling a libusb function.
380 * However, an asynchronous model requires that libusb perform work at various
381 * points in time - namely processing the results of previously-submitted
382 * transfers and invoking the user-supplied callback function.
384 * This gives rise to the libusb_poll() function which your
385 * application must call into when libusb has work do to. This gives libusb
386 * the opportunity to reap pending transfers, invoke callbacks, etc.
388 * The first issue to discuss here is how your application can figure out
389 * when libusb has work to do. In fact, there are two naive options which
390 * do not actually require your application to know this:
391 * -# Periodically call libusb_poll() in non-blocking mode at fixed short
392 * intervals from your main loop
393 * -# Repeatedly call libusb_poll() in blocking mode from a dedicated thread.
395 * The first option is plainly not very nice, and will cause unnecessary
396 * CPU wakeups leading to increased power usage and decreased battery life.
397 * The second option is not very nice either, but may be the nicest option
398 * available to you if the "proper" approach can not be applied to your
399 * application (read on...).
401 * The recommended option is to integrate libusb with your application main
402 * event loop. libusb exposes a set of file descriptors which allow you to do
403 * this. Your main loop is probably already calling poll() or select() or a
404 * variant on a set of file descriptors for other event sources (e.g. keyboard
405 * button presses, mouse movements, network sockets, etc). You then add
406 * libusb's file descriptors to your poll()/select() calls, and when activity
407 * is detected on such descriptors you know it is time to call
410 * There is one final event handling complication. libusb supports
411 * asynchronous transfers which time out after a specified time period, and
412 * this requires that libusb is called into at or after the timeout so that
413 * the timeout can be handled. So, in addition to considering libusb's file
414 * descriptors in your main event loop, you must also consider that libusb
415 * sometimes needs to be called into at fixed points in time even when there
416 * is no file descriptor activity.
418 * For the details on retrieving the set of file descriptors and determining
419 * the next timeout, see the \ref poll "polling and timing" API documentation.
423 * @defgroup poll Polling and timing
425 * This page documents libusb's functions for polling events and timing.
426 * These functions are only necessary for users of the
427 * \ref asyncio "asynchronous API". If you are only using the simpler
428 * \ref syncio "synchronous API" then you do not need to ever call these
431 * The justification for the functionality described here has already been
432 * discussed in the \ref asyncevent "event handling" section of the
433 * asynchronous API documentation. In summary, libusb does not create internal
434 * threads for event processing and hence relies on your application calling
435 * into libusb at certain points in time so that pending events can be handled.
436 * In order to know precisely when libusb needs to be called into, libusb
437 * offers you a set of pollable file descriptors and information about when
438 * the next timeout expires.
440 * If you are using the asynchronous I/O API, you must take one of the two
441 * following options, otherwise your I/O will not complete.
443 * \section pollsimple The simple option
445 * If your application revolves solely around libusb and does not need to
446 * handle other event sources, you can have a program structure as follows:
449 // find and open device
450 // maybe fire off some initial async I/O
452 while (user_has_not_requested_exit)
458 * With such a simple main loop, you do not have to worry about managing
459 * sets of file descriptors or handling timeouts. libusb_poll() will handle
460 * those details internally.
462 * \section pollmain The more advanced option
464 * In more advanced applications, you will already have a main loop which
465 * is monitoring other event sources: network sockets, X11 events, mouse
466 * movements, etc. Through exposing a set of file descriptors, libusb is
467 * designed to cleanly integrate into such main loops.
469 * In addition to polling file descriptors for the other event sources, you
470 * take a set of file descriptors from libusb and monitor those too. When you
471 * detect activity on libusb's file descriptors, you call libusb_poll_timeout()
472 * in non-blocking mode.
474 * You must also consider the fact that libusb sometimes has to handle events
475 * at certain known times which do not generate activity on file descriptors.
476 * Your main loop must also consider these times, modify it's poll()/select()
477 * timeout accordingly, and track time so that libusb_poll_timeout() is called
478 * in non-blocking mode when timeouts expire.
480 * In pseudo-code, you want something that looks like:
485 while (user has not requested application exit):
486 libusb_get_next_timeout()
487 select(on libusb file descriptors plus any other event sources of interest,
488 using a timeout no larger than the value libusb just suggested)
489 if (select() indicated activity on libusb file descriptors):
490 libusb_poll_timeout(0);
491 if (time has elapsed to or beyond the libusb timeout):
492 libusb_poll_timeout(0);
497 * The set of file descriptors that libusb uses as event sources may change
498 * during the life of your application. Rather than having to repeatedly
499 * call libusb_get_pollfds(), you can set up notification functions for when
500 * the file descriptor set changes using libusb_set_pollfd_notifiers().
506 list_init(&flying_transfers);
509 fd_removed_cb = NULL;
512 static int calculate_timeout(struct usbi_transfer *transfer)
515 struct timespec current_time;
516 unsigned int timeout = transfer->pub.timeout;
521 r = clock_gettime(CLOCK_MONOTONIC, ¤t_time);
523 usbi_err("failed to read monotonic clock, errno=%d", errno);
527 current_time.tv_sec += timeout / 1000;
528 current_time.tv_nsec += (timeout % 1000) * 1000000;
530 if (current_time.tv_nsec > 1000000000) {
531 current_time.tv_nsec -= 1000000000;
532 current_time.tv_sec++;
535 TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time);
539 static void add_to_flying_list(struct usbi_transfer *transfer)
541 struct usbi_transfer *cur;
542 struct timeval *timeout = &transfer->timeout;
544 /* if we have no other flying transfers, start the list with this one */
545 if (list_empty(&flying_transfers)) {
546 list_add(&transfer->list, &flying_transfers);
550 /* if we have infinite timeout, append to end of list */
551 if (!timerisset(timeout)) {
552 list_add_tail(&transfer->list, &flying_transfers);
556 /* otherwise, find appropriate place in list */
557 list_for_each_entry(cur, &flying_transfers, list) {
558 /* find first timeout that occurs after the transfer in question */
559 struct timeval *cur_tv = &cur->timeout;
561 if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
562 (cur_tv->tv_sec == timeout->tv_sec &&
563 cur_tv->tv_usec > timeout->tv_usec)) {
564 list_add_tail(&transfer->list, &cur->list);
569 /* otherwise we need to be inserted at the end */
570 list_add_tail(&transfer->list, &flying_transfers);
573 static int submit_transfer(struct usbi_transfer *itransfer)
575 int r = usbi_backend->submit_transfer(itransfer);
579 add_to_flying_list(itransfer);
584 * Obtain the memory-resident size of a transfer structure. Normally, you do
585 * not care about this as you will use libusb_alloc_transfer() and
586 * libusb_free_transfer() which hide this implementation detail from you.
588 * This function is useful when you wish to allocate transfers using your
589 * own custom memory allocator. libusb's transfer structure is bigger than
590 * it appears, so you must use this function to find out how much space is
591 * required for each transfer allocation.
593 * If you are allocating your own transfers, remember to initialize them
594 * with libusb_init_transfer().
596 * \returns the true size of a libusb_transfer structure
598 API_EXPORTED size_t libusb_get_transfer_alloc_size(void)
600 return sizeof(struct usbi_transfer) + usbi_backend->transfer_priv_size;
603 void __init_transfer(struct usbi_transfer *transfer)
605 memset(transfer, 0, sizeof(*transfer));
609 * Initialize a libusb transfer. This function is only for users who allocate
610 * their transfers using their own memory allocator. The more standard
611 * libusb_alloc_transfer() returns pre-initialized transfers.
612 * \param transfer a transfer to initialize
614 API_EXPORTED void libusb_init_transfer(struct libusb_transfer *transfer)
616 __init_transfer(TRANSFER_TO_PRIV(transfer));
620 * Allocate a libusb transfer using the standard system memory allocator. The
621 * returned transfer is pre-initialized for you. When the new transfer is no
622 * longer needed, it should be freed with libusb_free_transfer().
625 * Instead of using this function, it is legal for you to allocate transfers
626 * using a memory allocator of your choosing, but only if you consider the
627 * hidden size requirement (see libusb_get_transfer_alloc_size()) and
628 * initialize them before use (see libusb_init_transfer()).
630 * \returns a newly allocated transfer, or NULL on error
632 API_EXPORTED struct libusb_transfer *libusb_alloc_transfer(void)
634 struct usbi_transfer *transfer =
635 malloc(sizeof(*transfer) + usbi_backend->transfer_priv_size);
639 __init_transfer(transfer);
640 return &transfer->pub;
644 * Free a transfer structure. This should be called for all transfers
645 * allocated with libusb_alloc_transfer().
647 * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
648 * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
649 * non-NULL, this function will also free the transfer buffer using the
650 * standard system memory allocator (e.g. free()).
652 * It is legal to call this function with a NULL transfer. In this case,
653 * the function will simply return safely.
655 * \param transfer the transfer to free
657 API_EXPORTED void libusb_free_transfer(struct libusb_transfer *transfer)
659 struct usbi_transfer *itransfer;
663 if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
664 free(transfer->buffer);
666 itransfer = TRANSFER_TO_PRIV(transfer);
671 * Submit a transfer. This function will fire off the USB transfer and then
672 * return immediately.
674 * It is undefined behaviour to submit a transfer that has already been
675 * submitted but has not yet completed.
677 * \param transfer the transfer to submit
678 * \returns 0 on success
679 * \returns negative on error
681 API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)
683 struct usbi_transfer *itransfer = TRANSFER_TO_PRIV(transfer);
686 itransfer->transferred = 0;
687 r = calculate_timeout(itransfer);
691 if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL) {
692 struct libusb_control_setup *setup =
693 (struct libusb_control_setup *) transfer->buffer;
695 usbi_dbg("RQT=%02x RQ=%02x VAL=%04x IDX=%04x length=%d",
696 setup->bRequestType, setup->bRequest, setup->wValue, setup->wIndex,
699 setup->wValue = cpu_to_le16(setup->wValue);
700 setup->wIndex = cpu_to_le16(setup->wIndex);
701 setup->wLength = cpu_to_le16(setup->wLength);
704 return submit_transfer(itransfer);
708 * Asynchronously cancel a previously submitted transfer.
709 * It is undefined behaviour to call this function on a transfer that is
710 * already being cancelled or has already completed.
711 * This function returns immediately, but this does not indicate cancellation
712 * is complete. Your callback function will be invoked at some later time
713 * with a transfer status of
714 * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
715 * "LIBUSB_TRANSFER_CANCELLED."
717 * \param transfer the transfer to cancel
718 * \returns 0 on success
719 * \returns non-zero on error
721 API_EXPORTED int libusb_cancel_transfer(struct libusb_transfer *transfer)
723 struct usbi_transfer *itransfer = TRANSFER_TO_PRIV(transfer);
727 r = usbi_backend->cancel_transfer(itransfer);
729 usbi_err("cancel transfer failed error %d", r);
734 * Cancel a transfer and wait for cancellation completion without invoking
735 * the transfer callback. This function will block.
737 * It is undefined behaviour to call this function on a transfer that is
738 * already being cancelled or has already completed.
740 * \param transfer the transfer to cancel
741 * \returns 0 on success
742 * \returns non-zero on error
744 API_EXPORTED int libusb_cancel_transfer_sync(struct libusb_transfer *transfer)
746 struct usbi_transfer *itransfer = TRANSFER_TO_PRIV(transfer);
750 r = usbi_backend->cancel_transfer(itransfer);
752 usbi_err("cancel transfer failed error %d", r);
756 itransfer->flags |= USBI_TRANSFER_SYNC_CANCELLED;
757 while (itransfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
766 void usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
767 enum libusb_transfer_status status)
769 struct libusb_transfer *transfer = &itransfer->pub;
772 if (status == LIBUSB_TRANSFER_SILENT_COMPLETION)
775 if (status == LIBUSB_TRANSFER_COMPLETED
776 && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
777 int rqlen = transfer->length;
778 if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL)
779 rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
780 if (rqlen != itransfer->transferred) {
781 usbi_dbg("interpreting short transfer as error");
782 status = LIBUSB_TRANSFER_ERROR;
786 flags = transfer->flags;
787 transfer->status = status;
788 transfer->actual_length = itransfer->transferred;
789 if (transfer->callback)
790 transfer->callback(transfer);
791 /* transfer might have been freed by the above call, do not use from
793 if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
794 libusb_free_transfer(transfer);
797 void usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
799 /* if the URB is being cancelled synchronously, raise cancellation
800 * completion event by unsetting flag, and ensure that user callback does
803 if (transfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
804 transfer->flags &= ~USBI_TRANSFER_SYNC_CANCELLED;
805 usbi_dbg("detected sync. cancel");
806 usbi_handle_transfer_completion(transfer,
807 LIBUSB_TRANSFER_SILENT_COMPLETION);
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 /* handling timeouts is tricky, as we may race with the kernel: we may
825 * detect a timeout racing with the condition that the urb has actually
826 * completed. we asynchronously cancel the URB and report timeout
827 * to the user when the URB cancellation completes (or not at all if the
828 * URB actually gets delivered as per this race) */
829 struct libusb_transfer *transfer = &itransfer->pub;
832 itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
833 r = libusb_cancel_transfer(transfer);
835 usbi_warn("async cancel failed %d errno=%d", r, errno);
838 static int handle_timeouts(void)
840 struct timespec systime_ts;
841 struct timeval systime;
842 struct usbi_transfer *transfer;
845 if (list_empty(&flying_transfers))
848 /* get current time */
849 r = clock_gettime(CLOCK_MONOTONIC, &systime_ts);
853 TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
855 /* iterate through flying transfers list, finding all transfers that
856 * have expired timeouts */
857 list_for_each_entry(transfer, &flying_transfers, list) {
858 struct timeval *cur_tv = &transfer->timeout;
860 /* if we've reached transfers of infinite timeout, we're all done */
861 if (!timerisset(cur_tv))
864 /* ignore timeouts we've already handled */
865 if (transfer->flags & USBI_TRANSFER_TIMED_OUT)
868 /* if transfer has non-expired timeout, nothing more to do */
869 if ((cur_tv->tv_sec > systime.tv_sec) ||
870 (cur_tv->tv_sec == systime.tv_sec &&
871 cur_tv->tv_usec > systime.tv_usec))
874 /* otherwise, we've got an expired timeout to handle */
875 handle_timeout(transfer);
881 static int poll_io(struct timeval *tv)
885 fd_set readfds, writefds;
886 fd_set *_readfds = NULL;
887 fd_set *_writefds = NULL;
888 struct usbi_pollfd *ipollfd;
889 int have_readfds = 0;
890 int have_writefds = 0;
891 struct timeval select_timeout;
892 struct timeval timeout;
894 r = libusb_get_next_timeout(&timeout);
896 /* timeout already expired? */
897 if (!timerisset(&timeout))
898 return handle_timeouts();
900 /* choose the smallest of next URB timeout or user specified timeout */
901 if (timercmp(&timeout, tv, <))
902 select_timeout = timeout;
904 select_timeout = *tv;
906 select_timeout = *tv;
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);
929 _writefds = &writefds;
931 usbi_dbg("select() with timeout in %d.%06ds", select_timeout.tv_sec,
932 select_timeout.tv_usec);
933 r = select(maxfd + 1, _readfds, _writefds, NULL, &select_timeout);
934 usbi_dbg("select() returned %d with %d.%06ds remaining",
935 r, select_timeout.tv_sec, select_timeout.tv_usec);
937 *tv = select_timeout;
938 return handle_timeouts();
939 } else if (r == -1 && errno == EINTR) {
942 usbi_err("select failed %d err=%d\n", r, errno);
946 r = usbi_backend->handle_events(_readfds, _writefds);
950 /* FIXME check return value? */
951 return handle_timeouts();
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
971 * \returns non-zero on error
973 API_EXPORTED int libusb_poll_timeout(struct timeval *tv)
979 * Handle any pending events in blocking mode with a sensible timeout. This
980 * timeout is currently hardcoded at 2 seconds but we may change this if we
981 * decide other values are more sensible. For finer control over whether this
982 * function is blocking or non-blocking, or the maximum timeout, use
983 * libusb_poll_timeout() instead.
985 * \returns 0 on success
986 * \returns non-zero on error
988 API_EXPORTED int libusb_poll(void)
997 * Determine the next internal timeout that libusb needs to handle. You only
998 * need to use this function if you are calling poll() or select() or similar
999 * on libusb's file descriptors yourself - you do not need to use it if you
1000 * are calling libusb_poll() or a variant directly.
1002 * You should call this function in your main loop in order to determine how
1003 * long to wait for select() or poll() to return results. libusb needs to be
1004 * called into at this timeout, so you should use it as an upper bound on
1005 * your select() or poll() call.
1007 * When the timeout has expired, call into libusb_poll_timeout() (perhaps in
1008 * non-blocking mode) so that libusb can handle the timeout.
1010 * This function may return 0 (success) and an all-zero timeval. If this is
1011 * the case, it indicates that libusb has a timeout that has already expired
1012 * so you should call libusb_poll_timeout() or similar immediately.
1014 * \param tv output location for a relative time against the current
1015 * clock in which libusb must be called into in order to process timeout events
1016 * \returns 0 on success
1017 * \returns non-zero on error
1019 API_EXPORTED int libusb_get_next_timeout(struct timeval *tv)
1021 struct usbi_transfer *transfer;
1022 struct timespec cur_ts;
1023 struct timeval cur_tv;
1024 struct timeval *next_timeout;
1028 if (list_empty(&flying_transfers)) {
1029 usbi_dbg("no URBs, no timeout!");
1033 /* find next transfer which hasn't already been processed as timed out */
1034 list_for_each_entry(transfer, &flying_transfers, list) {
1035 if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) {
1042 usbi_dbg("all URBs have already been processed for timeouts");
1046 next_timeout = &transfer->timeout;
1048 /* no timeout for next transfer */
1049 if (!timerisset(next_timeout)) {
1050 usbi_dbg("no URBs with timeouts, no timeout!");
1054 r = clock_gettime(CLOCK_MONOTONIC, &cur_ts);
1056 usbi_err("failed to read monotonic clock, errno=%d", errno);
1059 TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
1061 if (timercmp(&cur_tv, next_timeout, >=)) {
1062 usbi_dbg("first timeout already expired");
1065 timersub(next_timeout, &cur_tv, tv);
1066 usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
1073 * Register notification functions for file descriptor additions/removals.
1074 * These functions will be invoked for every new or removed file descriptor
1075 * that libusb uses as an event source.
1077 * To remove notifiers, pass NULL values for the function pointers.
1079 * \param added_cb pointer to function for addition notifications
1080 * \param removed_cb pointer to function for removal notifications
1082 API_EXPORTED void libusb_set_pollfd_notifiers(libusb_pollfd_added_cb added_cb,
1083 libusb_pollfd_removed_cb removed_cb)
1085 fd_added_cb = added_cb;
1086 fd_removed_cb = removed_cb;
1089 int usbi_add_pollfd(int fd, short events)
1091 struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
1095 usbi_dbg("add fd %d events %d", fd, events);
1096 ipollfd->pollfd.fd = fd;
1097 ipollfd->pollfd.events = events;
1098 list_add(&ipollfd->list, &pollfds);
1101 fd_added_cb(fd, events);
1105 void usbi_remove_pollfd(int fd)
1107 struct usbi_pollfd *ipollfd;
1110 usbi_dbg("remove fd %d", fd);
1111 list_for_each_entry(ipollfd, &pollfds, list)
1112 if (ipollfd->pollfd.fd == fd) {
1118 usbi_err("couldn't find fd %d to remove", fd);
1122 list_del(&ipollfd->list);
1129 * Retrieve a list of file descriptors that should be polled by your main loop
1130 * as libusb event sources.
1132 * The returned list is NULL-terminated and should be freed with free() when
1133 * done. The actual list contents must not be touched.
1135 * \returns a NULL-terminated list of libusb_pollfd structures, or NULL on
1138 API_EXPORTED struct libusb_pollfd **libusb_get_pollfds(void)
1140 struct libusb_pollfd **ret;
1141 struct usbi_pollfd *ipollfd;
1145 list_for_each_entry(ipollfd, &pollfds, list)
1148 ret = calloc(cnt + 1, sizeof(struct libusb_pollfd *));
1152 list_for_each_entry(ipollfd, &pollfds, list)
1153 ret[i++] = (struct libusb_pollfd *) ipollfd;