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Diffstat (limited to 'libusb-1.0/libusb/io.c')
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diff --git a/libusb-1.0/libusb/io.c b/libusb-1.0/libusb/io.c deleted file mode 100644 index d4f6f3d..0000000 --- a/libusb-1.0/libusb/io.c +++ /dev/null @@ -1,2366 +0,0 @@ -/* - * I/O functions for libusb - * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org> - * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com> - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; either - * version 2.1 of the License, or (at your option) any later version. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA - */ - -#include <config.h> -#include <errno.h> -#include <signal.h> -#include <stdint.h> -#include <stdlib.h> -#include <string.h> -#include <time.h> - -#ifdef HAVE_SYS_TIME_H -#include <sys/time.h> -#endif - -#ifdef USBI_TIMERFD_AVAILABLE -#include <sys/timerfd.h> -#endif - -#include "libusbi.h" - -/** - * \page io Synchronous and asynchronous device I/O - * - * \section intro Introduction - * - * If you're using libusb in your application, you're probably wanting to - * perform I/O with devices - you want to perform USB data transfers. - * - * libusb offers two separate interfaces for device I/O. This page aims to - * introduce the two in order to help you decide which one is more suitable - * for your application. You can also choose to use both interfaces in your - * application by considering each transfer on a case-by-case basis. - * - * Once you have read through the following discussion, you should consult the - * detailed API documentation pages for the details: - * - \ref syncio - * - \ref asyncio - * - * \section theory Transfers at a logical level - * - * At a logical level, USB transfers typically happen in two parts. For - * example, when reading data from a endpoint: - * -# A request for data is sent to the device - * -# Some time later, the incoming data is received by the host - * - * or when writing data to an endpoint: - * - * -# The data is sent to the device - * -# Some time later, the host receives acknowledgement from the device that - * the data has been transferred. - * - * There may be an indefinite delay between the two steps. Consider a - * fictional USB input device with a button that the user can press. In order - * to determine when the button is pressed, you would likely submit a request - * to read data on a bulk or interrupt endpoint and wait for data to arrive. - * Data will arrive when the button is pressed by the user, which is - * potentially hours later. - * - * libusb offers both a synchronous and an asynchronous interface to performing - * USB transfers. The main difference is that the synchronous interface - * combines both steps indicated above into a single function call, whereas - * the asynchronous interface separates them. - * - * \section sync The synchronous interface - * - * The synchronous I/O interface allows you to perform a USB transfer with - * a single function call. When the function call returns, the transfer has - * completed and you can parse the results. - * - * If you have used the libusb-0.1 before, this I/O style will seem familar to - * you. libusb-0.1 only offered a synchronous interface. - * - * In our input device example, to read button presses you might write code - * in the following style: -\code -unsigned char data[4]; -int actual_length, -int r = libusb_bulk_transfer(handle, EP_IN, data, sizeof(data), &actual_length, 0); -if (r == 0 && actual_length == sizeof(data)) { - // results of the transaction can now be found in the data buffer - // parse them here and report button press -} else { - error(); -} -\endcode - * - * The main advantage of this model is simplicity: you did everything with - * a single simple function call. - * - * However, this interface has its limitations. Your application will sleep - * inside libusb_bulk_transfer() until the transaction has completed. If it - * takes the user 3 hours to press the button, your application will be - * sleeping for that long. Execution will be tied up inside the library - - * the entire thread will be useless for that duration. - * - * Another issue is that by tieing up the thread with that single transaction - * there is no possibility of performing I/O with multiple endpoints and/or - * multiple devices simultaneously, unless you resort to creating one thread - * per transaction. - * - * Additionally, there is no opportunity to cancel the transfer after the - * request has been submitted. - * - * For details on how to use the synchronous API, see the - * \ref syncio "synchronous I/O API documentation" pages. - * - * \section async The asynchronous interface - * - * Asynchronous I/O is the most significant new feature in libusb-1.0. - * Although it is a more complex interface, it solves all the issues detailed - * above. - * - * Instead of providing which functions that block until the I/O has complete, - * libusb's asynchronous interface presents non-blocking functions which - * begin a transfer and then return immediately. Your application passes a - * callback function pointer to this non-blocking function, which libusb will - * call with the results of the transaction when it has completed. - * - * Transfers which have been submitted through the non-blocking functions - * can be cancelled with a separate function call. - * - * The non-blocking nature of this interface allows you to be simultaneously - * performing I/O to multiple endpoints on multiple devices, without having - * to use threads. - * - * This added flexibility does come with some complications though: - * - In the interest of being a lightweight library, libusb does not create - * threads and can only operate when your application is calling into it. Your - * application must call into libusb from it's main loop when events are ready - * to be handled, or you must use some other scheme to allow libusb to - * undertake whatever work needs to be done. - * - libusb also needs to be called into at certain fixed points in time in - * order to accurately handle transfer timeouts. - * - Memory handling becomes more complex. You cannot use stack memory unless - * the function with that stack is guaranteed not to return until the transfer - * callback has finished executing. - * - You generally lose some linearity from your code flow because submitting - * the transfer request is done in a separate function from where the transfer - * results are handled. This becomes particularly obvious when you want to - * submit a second transfer based on the results of an earlier transfer. - * - * Internally, libusb's synchronous interface is expressed in terms of function - * calls to the asynchronous interface. - * - * For details on how to use the asynchronous API, see the - * \ref asyncio "asynchronous I/O API" documentation pages. - */ - - -/** - * \page packetoverflow Packets and overflows - * - * \section packets Packet abstraction - * - * The USB specifications describe how data is transmitted in packets, with - * constraints on packet size defined by endpoint descriptors. The host must - * not send data payloads larger than the endpoint's maximum packet size. - * - * libusb and the underlying OS abstract out the packet concept, allowing you - * to request transfers of any size. Internally, the request will be divided - * up into correctly-sized packets. You do not have to be concerned with - * packet sizes, but there is one exception when considering overflows. - * - * \section overflow Bulk/interrupt transfer overflows - * - * When requesting data on a bulk endpoint, libusb requires you to supply a - * buffer and the maximum number of bytes of data that libusb can put in that - * buffer. However, the size of the buffer is not communicated to the device - - * the device is just asked to send any amount of data. - * - * There is no problem if the device sends an amount of data that is less than - * or equal to the buffer size. libusb reports this condition to you through - * the \ref libusb_transfer::actual_length "libusb_transfer.actual_length" - * field. - * - * Problems may occur if the device attempts to send more data than can fit in - * the buffer. libusb reports LIBUSB_TRANSFER_OVERFLOW for this condition but - * other behaviour is largely undefined: actual_length may or may not be - * accurate, the chunk of data that can fit in the buffer (before overflow) - * may or may not have been transferred. - * - * Overflows are nasty, but can be avoided. Even though you were told to - * ignore packets above, think about the lower level details: each transfer is - * split into packets (typically small, with a maximum size of 512 bytes). - * Overflows can only happen if the final packet in an incoming data transfer - * is smaller than the actual packet that the device wants to transfer. - * Therefore, you will never see an overflow if your transfer buffer size is a - * multiple of the endpoint's packet size: the final packet will either - * fill up completely or will be only partially filled. - */ - -/** - * @defgroup asyncio Asynchronous device I/O - * - * This page details libusb's asynchronous (non-blocking) API for USB device - * I/O. This interface is very powerful but is also quite complex - you will - * need to read this page carefully to understand the necessary considerations - * and issues surrounding use of this interface. Simplistic applications - * may wish to consider the \ref syncio "synchronous I/O API" instead. - * - * The asynchronous interface is built around the idea of separating transfer - * submission and handling of transfer completion (the synchronous model - * combines both of these into one). There may be a long delay between - * submission and completion, however the asynchronous submission function - * is non-blocking so will return control to your application during that - * potentially long delay. - * - * \section asyncabstraction Transfer abstraction - * - * For the asynchronous I/O, libusb implements the concept of a generic - * transfer entity for all types of I/O (control, bulk, interrupt, - * isochronous). The generic transfer object must be treated slightly - * differently depending on which type of I/O you are performing with it. - * - * This is represented by the public libusb_transfer structure type. - * - * \section asynctrf Asynchronous transfers - * - * We can view asynchronous I/O as a 5 step process: - * -# <b>Allocation</b>: allocate a libusb_transfer - * -# <b>Filling</b>: populate the libusb_transfer instance with information - * about the transfer you wish to perform - * -# <b>Submission</b>: ask libusb to submit the transfer - * -# <b>Completion handling</b>: examine transfer results in the - * libusb_transfer structure - * -# <b>Deallocation</b>: clean up resources - * - * - * \subsection asyncalloc Allocation - * - * This step involves allocating memory for a USB transfer. This is the - * generic transfer object mentioned above. At this stage, the transfer - * is "blank" with no details about what type of I/O it will be used for. - * - * Allocation is done with the libusb_alloc_transfer() function. You must use - * this function rather than allocating your own transfers. - * - * \subsection asyncfill Filling - * - * This step is where you take a previously allocated transfer and fill it - * with information to determine the message type and direction, data buffer, - * callback function, etc. - * - * You can either fill the required fields yourself or you can use the - * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer() - * and libusb_fill_interrupt_transfer(). - * - * \subsection asyncsubmit Submission - * - * When you have allocated a transfer and filled it, you can submit it using - * libusb_submit_transfer(). This function returns immediately but can be - * regarded as firing off the I/O request in the background. - * - * \subsection asynccomplete Completion handling - * - * After a transfer has been submitted, one of four things can happen to it: - * - * - The transfer completes (i.e. some data was transferred) - * - The transfer has a timeout and the timeout expires before all data is - * transferred - * - The transfer fails due to an error - * - The transfer is cancelled - * - * Each of these will cause the user-specified transfer callback function to - * be invoked. It is up to the callback function to determine which of the - * above actually happened and to act accordingly. - * - * The user-specified callback is passed a pointer to the libusb_transfer - * structure which was used to setup and submit the transfer. At completion - * time, libusb has populated this structure with results of the transfer: - * success or failure reason, number of bytes of data transferred, etc. See - * the libusb_transfer structure documentation for more information. - * - * \subsection Deallocation - * - * When a transfer has completed (i.e. the callback function has been invoked), - * you are advised to free the transfer (unless you wish to resubmit it, see - * below). Transfers are deallocated with libusb_free_transfer(). - * - * It is undefined behaviour to free a transfer which has not completed. - * - * \section asyncresubmit Resubmission - * - * You may be wondering why allocation, filling, and submission are all - * separated above where they could reasonably be combined into a single - * operation. - * - * The reason for separation is to allow you to resubmit transfers without - * having to allocate new ones every time. This is especially useful for - * common situations dealing with interrupt endpoints - you allocate one - * transfer, fill and submit it, and when it returns with results you just - * resubmit it for the next interrupt. - * - * \section asynccancel Cancellation - * - * Another advantage of using the asynchronous interface is that you have - * the ability to cancel transfers which have not yet completed. This is - * done by calling the libusb_cancel_transfer() function. - * - * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the - * cancellation actually completes, the transfer's callback function will - * be invoked, and the callback function should check the transfer status to - * determine that it was cancelled. - * - * Freeing the transfer after it has been cancelled but before cancellation - * has completed will result in undefined behaviour. - * - * When a transfer is cancelled, some of the data may have been transferred. - * libusb will communicate this to you in the transfer callback. Do not assume - * that no data was transferred. - * - * \section bulk_overflows Overflows on device-to-host bulk/interrupt endpoints - * - * If your device does not have predictable transfer sizes (or it misbehaves), - * your application may submit a request for data on an IN endpoint which is - * smaller than the data that the device wishes to send. In some circumstances - * this will cause an overflow, which is a nasty condition to deal with. See - * the \ref packetoverflow page for discussion. - * - * \section asyncctrl Considerations for control transfers - * - * The <tt>libusb_transfer</tt> structure is generic and hence does not - * include specific fields for the control-specific setup packet structure. - * - * In order to perform a control transfer, you must place the 8-byte setup - * packet at the start of the data buffer. To simplify this, you could - * cast the buffer pointer to type struct libusb_control_setup, or you can - * use the helper function libusb_fill_control_setup(). - * - * The wLength field placed in the setup packet must be the length you would - * expect to be sent in the setup packet: the length of the payload that - * follows (or the expected maximum number of bytes to receive). However, - * the length field of the libusb_transfer object must be the length of - * the data buffer - i.e. it should be wLength <em>plus</em> the size of - * the setup packet (LIBUSB_CONTROL_SETUP_SIZE). - * - * If you use the helper functions, this is simplified for you: - * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the - * data you are sending/requesting. - * -# Call libusb_fill_control_setup() on the data buffer, using the transfer - * request size as the wLength value (i.e. do not include the extra space you - * allocated for the control setup). - * -# If this is a host-to-device transfer, place the data to be transferred - * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE. - * -# Call libusb_fill_control_transfer() to associate the data buffer with - * the transfer (and to set the remaining details such as callback and timeout). - * - Note that there is no parameter to set the length field of the transfer. - * The length is automatically inferred from the wLength field of the setup - * packet. - * -# Submit the transfer. - * - * The multi-byte control setup fields (wValue, wIndex and wLength) must - * be given in little-endian byte order (the endianness of the USB bus). - * Endianness conversion is transparently handled by - * libusb_fill_control_setup() which is documented to accept host-endian - * values. - * - * Further considerations are needed when handling transfer completion in - * your callback function: - * - As you might expect, the setup packet will still be sitting at the start - * of the data buffer. - * - If this was a device-to-host transfer, the received data will be sitting - * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer. - * - The actual_length field of the transfer structure is relative to the - * wLength of the setup packet, rather than the size of the data buffer. So, - * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you - * should expect an <tt>actual_length</tt> of 4 to indicate that the data was - * transferred in entirity. - * - * To simplify parsing of setup packets and obtaining the data from the - * correct offset, you may wish to use the libusb_control_transfer_get_data() - * and libusb_control_transfer_get_setup() functions within your transfer - * callback. - * - * Even though control endpoints do not halt, a completed control transfer - * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control - * request was not supported. - * - * \section asyncintr Considerations for interrupt transfers - * - * All interrupt transfers are performed using the polling interval presented - * by the bInterval value of the endpoint descriptor. - * - * \section asynciso Considerations for isochronous transfers - * - * Isochronous transfers are more complicated than transfers to - * non-isochronous endpoints. - * - * To perform I/O to an isochronous endpoint, allocate the transfer by calling - * libusb_alloc_transfer() with an appropriate number of isochronous packets. - * - * During filling, set \ref libusb_transfer::type "type" to - * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS - * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set - * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than - * or equal to the number of packets you requested during allocation. - * libusb_alloc_transfer() does not set either of these fields for you, given - * that you might not even use the transfer on an isochronous endpoint. - * - * Next, populate the length field for the first num_iso_packets entries in - * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section - * 5.6.3 of the USB2 specifications describe how the maximum isochronous - * packet length is determined by the wMaxPacketSize field in the endpoint - * descriptor. - * Two functions can help you here: - * - * - libusb_get_max_iso_packet_size() is an easy way to determine the max - * packet size for an isochronous endpoint. Note that the maximum packet - * size is actually the maximum number of bytes that can be transmitted in - * a single microframe, therefore this function multiplies the maximum number - * of bytes per transaction by the number of transaction opportunities per - * microframe. - * - libusb_set_iso_packet_lengths() assigns the same length to all packets - * within a transfer, which is usually what you want. - * - * For outgoing transfers, you'll obviously fill the buffer and populate the - * packet descriptors in hope that all the data gets transferred. For incoming - * transfers, you must ensure the buffer has sufficient capacity for - * the situation where all packets transfer the full amount of requested data. - * - * Completion handling requires some extra consideration. The - * \ref libusb_transfer::actual_length "actual_length" field of the transfer - * is meaningless and should not be examined; instead you must refer to the - * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of - * each individual packet. - * - * The \ref libusb_transfer::status "status" field of the transfer is also a - * little misleading: - * - If the packets were submitted and the isochronous data microframes - * completed normally, status will have value - * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED - * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred - * delays are not counted as transfer errors; the transfer.status field may - * indicate COMPLETED even if some or all of the packets failed. Refer to - * the \ref libusb_iso_packet_descriptor::status "status" field of each - * individual packet to determine packet failures. - * - The status field will have value - * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR - * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered. - * - Other transfer status codes occur with normal behaviour. - * - * The data for each packet will be found at an offset into the buffer that - * can be calculated as if each prior packet completed in full. The - * libusb_get_iso_packet_buffer() and libusb_get_iso_packet_buffer_simple() - * functions may help you here. - * - * \section asyncmem Memory caveats - * - * In most circumstances, it is not safe to use stack memory for transfer - * buffers. This is because the function that fired off the asynchronous - * transfer may return before libusb has finished using the buffer, and when - * the function returns it's stack gets destroyed. This is true for both - * host-to-device and device-to-host transfers. - * - * The only case in which it is safe to use stack memory is where you can - * guarantee that the function owning the stack space for the buffer does not - * return until after the transfer's callback function has completed. In every - * other case, you need to use heap memory instead. - * - * \section asyncflags Fine control - * - * Through using this asynchronous interface, you may find yourself repeating - * a few simple operations many times. You can apply a bitwise OR of certain - * flags to a transfer to simplify certain things: - * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK - * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred - * less than the requested amount of data being marked with status - * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR" - * (they would normally be regarded as COMPLETED) - * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER - * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer - * buffer when freeing the transfer. - * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER - * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the - * transfer after the transfer callback returns. - * - * \section asyncevent Event handling - * - * In accordance of the aim of being a lightweight library, libusb does not - * create threads internally. This means that libusb code does not execute - * at any time other than when your application is calling a libusb function. - * However, an asynchronous model requires that libusb perform work at various - * points in time - namely processing the results of previously-submitted - * transfers and invoking the user-supplied callback function. - * - * This gives rise to the libusb_handle_events() function which your - * application must call into when libusb has work do to. This gives libusb - * the opportunity to reap pending transfers, invoke callbacks, etc. - * - * The first issue to discuss here is how your application can figure out - * when libusb has work to do. In fact, there are two naive options which - * do not actually require your application to know this: - * -# Periodically call libusb_handle_events() in non-blocking mode at fixed - * short intervals from your main loop - * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated - * thread. - * - * The first option is plainly not very nice, and will cause unnecessary - * CPU wakeups leading to increased power usage and decreased battery life. - * The second option is not very nice either, but may be the nicest option - * available to you if the "proper" approach can not be applied to your - * application (read on...). - * - * The recommended option is to integrate libusb with your application main - * event loop. libusb exposes a set of file descriptors which allow you to do - * this. Your main loop is probably already calling poll() or select() or a - * variant on a set of file descriptors for other event sources (e.g. keyboard - * button presses, mouse movements, network sockets, etc). You then add - * libusb's file descriptors to your poll()/select() calls, and when activity - * is detected on such descriptors you know it is time to call - * libusb_handle_events(). - * - * There is one final event handling complication. libusb supports - * asynchronous transfers which time out after a specified time period, and - * this requires that libusb is called into at or after the timeout so that - * the timeout can be handled. So, in addition to considering libusb's file - * descriptors in your main event loop, you must also consider that libusb - * sometimes needs to be called into at fixed points in time even when there - * is no file descriptor activity. - * - * For the details on retrieving the set of file descriptors and determining - * the next timeout, see the \ref poll "polling and timing" API documentation. - */ - -/** - * @defgroup poll Polling and timing - * - * This page documents libusb's functions for polling events and timing. - * These functions are only necessary for users of the - * \ref asyncio "asynchronous API". If you are only using the simpler - * \ref syncio "synchronous API" then you do not need to ever call these - * functions. - * - * The justification for the functionality described here has already been - * discussed in the \ref asyncevent "event handling" section of the - * asynchronous API documentation. In summary, libusb does not create internal - * threads for event processing and hence relies on your application calling - * into libusb at certain points in time so that pending events can be handled. - * In order to know precisely when libusb needs to be called into, libusb - * offers you a set of pollable file descriptors and information about when - * the next timeout expires. - * - * If you are using the asynchronous I/O API, you must take one of the two - * following options, otherwise your I/O will not complete. - * - * \section pollsimple The simple option - * - * If your application revolves solely around libusb and does not need to - * handle other event sources, you can have a program structure as follows: -\code -// initialize libusb -// find and open device -// maybe fire off some initial async I/O - -while (user_has_not_requested_exit) - libusb_handle_events(ctx); - -// clean up and exit -\endcode - * - * With such a simple main loop, you do not have to worry about managing - * sets of file descriptors or handling timeouts. libusb_handle_events() will - * handle those details internally. - * - * \section pollmain The more advanced option - * - * \note This functionality is currently only available on Unix-like platforms. - * On Windows, libusb_get_pollfds() simply returns NULL. Exposing event sources - * on Windows will require some further thought and design. - * - * In more advanced applications, you will already have a main loop which - * is monitoring other event sources: network sockets, X11 events, mouse - * movements, etc. Through exposing a set of file descriptors, libusb is - * designed to cleanly integrate into such main loops. - * - * In addition to polling file descriptors for the other event sources, you - * take a set of file descriptors from libusb and monitor those too. When you - * detect activity on libusb's file descriptors, you call - * libusb_handle_events_timeout() in non-blocking mode. - * - * What's more, libusb may also need to handle events at specific moments in - * time. No file descriptor activity is generated at these times, so your - * own application needs to be continually aware of when the next one of these - * moments occurs (through calling libusb_get_next_timeout()), and then it - * needs to call libusb_handle_events_timeout() in non-blocking mode when - * these moments occur. This means that you need to adjust your - * poll()/select() timeout accordingly. - * - * libusb provides you with a set of file descriptors to poll and expects you - * to poll all of them, treating them as a single entity. The meaning of each - * file descriptor in the set is an internal implementation detail, - * platform-dependent and may vary from release to release. Don't try and - * interpret the meaning of the file descriptors, just do as libusb indicates, - * polling all of them at once. - * - * In pseudo-code, you want something that looks like: -\code -// initialise libusb - -libusb_get_pollfds(ctx) -while (user has not requested application exit) { - libusb_get_next_timeout(ctx); - poll(on libusb file descriptors plus any other event sources of interest, - using a timeout no larger than the value libusb just suggested) - if (poll() indicated activity on libusb file descriptors) - libusb_handle_events_timeout(ctx, 0); - if (time has elapsed to or beyond the libusb timeout) - libusb_handle_events_timeout(ctx, 0); - // handle events from other sources here -} - -// clean up and exit -\endcode - * - * \subsection polltime Notes on time-based events - * - * The above complication with having to track time and call into libusb at - * specific moments is a bit of a headache. For maximum compatibility, you do - * need to write your main loop as above, but you may decide that you can - * restrict the supported platforms of your application and get away with - * a more simplistic scheme. - * - * These time-based event complications are \b not required on the following - * platforms: - * - Darwin - * - Linux, provided that the following version requirements are satisfied: - * - Linux v2.6.27 or newer, compiled with timerfd support - * - glibc v2.9 or newer - * - libusb v1.0.5 or newer - * - * Under these configurations, libusb_get_next_timeout() will \em always return - * 0, so your main loop can be simplified to: -\code -// initialise libusb - -libusb_get_pollfds(ctx) -while (user has not requested application exit) { - poll(on libusb file descriptors plus any other event sources of interest, - using any timeout that you like) - if (poll() indicated activity on libusb file descriptors) - libusb_handle_events_timeout(ctx, 0); - // handle events from other sources here -} - -// clean up and exit -\endcode - * - * Do remember that if you simplify your main loop to the above, you will - * lose compatibility with some platforms (including legacy Linux platforms, - * and <em>any future platforms supported by libusb which may have time-based - * event requirements</em>). The resultant problems will likely appear as - * strange bugs in your application. - * - * You can use the libusb_pollfds_handle_timeouts() function to do a runtime - * check to see if it is safe to ignore the time-based event complications. - * If your application has taken the shortcut of ignoring libusb's next timeout - * in your main loop, then you are advised to check the return value of - * libusb_pollfds_handle_timeouts() during application startup, and to abort - * if the platform does suffer from these timing complications. - * - * \subsection fdsetchange Changes in the file descriptor set - * - * The set of file descriptors that libusb uses as event sources may change - * during the life of your application. Rather than having to repeatedly - * call libusb_get_pollfds(), you can set up notification functions for when - * the file descriptor set changes using libusb_set_pollfd_notifiers(). - * - * \subsection mtissues Multi-threaded considerations - * - * Unfortunately, the situation is complicated further when multiple threads - * come into play. If two threads are monitoring the same file descriptors, - * the fact that only one thread will be woken up when an event occurs causes - * some headaches. - * - * The events lock, event waiters lock, and libusb_handle_events_locked() - * entities are added to solve these problems. You do not need to be concerned - * with these entities otherwise. - * - * See the extra documentation: \ref mtasync - */ - -/** \page mtasync Multi-threaded applications and asynchronous I/O - * - * libusb is a thread-safe library, but extra considerations must be applied - * to applications which interact with libusb from multiple threads. - * - * The underlying issue that must be addressed is that all libusb I/O - * revolves around monitoring file descriptors through the poll()/select() - * system calls. This is directly exposed at the - * \ref asyncio "asynchronous interface" but it is important to note that the - * \ref syncio "synchronous interface" is implemented on top of the - * asynchonrous interface, therefore the same considerations apply. - * - * The issue is that if two or more threads are concurrently calling poll() - * or select() on libusb's file descriptors then only one of those threads - * will be woken up when an event arrives. The others will be completely - * oblivious that anything has happened. - * - * Consider the following pseudo-code, which submits an asynchronous transfer - * then waits for its completion. This style is one way you could implement a - * synchronous interface on top of the asynchronous interface (and libusb - * does something similar, albeit more advanced due to the complications - * explained on this page). - * -\code -void cb(struct libusb_transfer *transfer) -{ - int *completed = transfer->user_data; - *completed = 1; -} - -void myfunc() { - struct libusb_transfer *transfer; - unsigned char buffer[LIBUSB_CONTROL_SETUP_SIZE]; - int completed = 0; - - transfer = libusb_alloc_transfer(0); - libusb_fill_control_setup(buffer, - LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT, 0x04, 0x01, 0, 0); - libusb_fill_control_transfer(transfer, dev, buffer, cb, &completed, 1000); - libusb_submit_transfer(transfer); - - while (!completed) { - poll(libusb file descriptors, 120*1000); - if (poll indicates activity) - libusb_handle_events_timeout(ctx, 0); - } - printf("completed!"); - // other code here -} -\endcode - * - * Here we are <em>serializing</em> completion of an asynchronous event - * against a condition - the condition being completion of a specific transfer. - * The poll() loop has a long timeout to minimize CPU usage during situations - * when nothing is happening (it could reasonably be unlimited). - * - * If this is the only thread that is polling libusb's file descriptors, there - * is no problem: there is no danger that another thread will swallow up the - * event that we are interested in. On the other hand, if there is another - * thread polling the same descriptors, there is a chance that it will receive - * the event that we were interested in. In this situation, <tt>myfunc()</tt> - * will only realise that the transfer has completed on the next iteration of - * the loop, <em>up to 120 seconds later.</em> Clearly a two-minute delay is - * undesirable, and don't even think about using short timeouts to circumvent - * this issue! - * - * The solution here is to ensure that no two threads are ever polling the - * file descriptors at the same time. A naive implementation of this would - * impact the capabilities of the library, so libusb offers the scheme - * documented below to ensure no loss of functionality. - * - * Before we go any further, it is worth mentioning that all libusb-wrapped - * event handling procedures fully adhere to the scheme documented below. - * This includes libusb_handle_events() and all the synchronous I/O functions - - * libusb hides this headache from you. You do not need to worry about any - * of these issues if you stick to that level. - * - * The problem is when we consider the fact that libusb exposes file - * descriptors to allow for you to integrate asynchronous USB I/O into - * existing main loops, effectively allowing you to do some work behind - * libusb's back. If you do take libusb's file descriptors and pass them to - * poll()/select() yourself, you need to be aware of the associated issues. - * - * \section eventlock The events lock - * - * The first concept to be introduced is the events lock. The events lock - * is used to serialize threads that want to handle events, such that only - * one thread is handling events at any one time. - * - * You must take the events lock before polling libusb file descriptors, - * using libusb_lock_events(). You must release the lock as soon as you have - * aborted your poll()/select() loop, using libusb_unlock_events(). - * - * \section threadwait Letting other threads do the work for you - * - * Although the events lock is a critical part of the solution, it is not - * enough on it's own. You might wonder if the following is sufficient... -\code - libusb_lock_events(ctx); - while (!completed) { - poll(libusb file descriptors, 120*1000); - if (poll indicates activity) - libusb_handle_events_timeout(ctx, 0); - } - libusb_unlock_events(ctx); -\endcode - * ...and the answer is that it is not. This is because the transfer in the - * code shown above may take a long time (say 30 seconds) to complete, and - * the lock is not released until the transfer is completed. - * - * Another thread with similar code that wants to do event handling may be - * working with a transfer that completes after a few milliseconds. Despite - * having such a quick completion time, the other thread cannot check that - * status of its transfer until the code above has finished (30 seconds later) - * due to contention on the lock. - * - * To solve this, libusb offers you a mechanism to determine when another - * thread is handling events. It also offers a mechanism to block your thread - * until the event handling thread has completed an event (and this mechanism - * does not involve polling of file descriptors). - * - * After determining that another thread is currently handling events, you - * obtain the <em>event waiters</em> lock using libusb_lock_event_waiters(). - * You then re-check that some other thread is still handling events, and if - * so, you call libusb_wait_for_event(). - * - * libusb_wait_for_event() puts your application to sleep until an event - * occurs, or until a thread releases the events lock. When either of these - * things happen, your thread is woken up, and should re-check the condition - * it was waiting on. It should also re-check that another thread is handling - * events, and if not, it should start handling events itself. - * - * This looks like the following, as pseudo-code: -\code -retry: -if (libusb_try_lock_events(ctx) == 0) { - // we obtained the event lock: do our own event handling - while (!completed) { - if (!libusb_event_handling_ok(ctx)) { - libusb_unlock_events(ctx); - goto retry; - } - poll(libusb file descriptors, 120*1000); - if (poll indicates activity) - libusb_handle_events_locked(ctx, 0); - } - libusb_unlock_events(ctx); -} else { - // another thread is doing event handling. wait for it to signal us that - // an event has completed - libusb_lock_event_waiters(ctx); - - while (!completed) { - // now that we have the event waiters lock, double check that another - // thread is still handling events for us. (it may have ceased handling - // events in the time it took us to reach this point) - if (!libusb_event_handler_active(ctx)) { - // whoever was handling events is no longer doing so, try again - libusb_unlock_event_waiters(ctx); - goto retry; - } - - libusb_wait_for_event(ctx, NULL); - } - libusb_unlock_event_waiters(ctx); -} -printf("completed!\n"); -\endcode - * - * A naive look at the above code may suggest that this can only support - * one event waiter (hence a total of 2 competing threads, the other doing - * event handling), because the event waiter seems to have taken the event - * waiters lock while waiting for an event. However, the system does support - * multiple event waiters, because libusb_wait_for_event() actually drops - * the lock while waiting, and reaquires it before continuing. - * - * We have now implemented code which can dynamically handle situations where - * nobody is handling events (so we should do it ourselves), and it can also - * handle situations where another thread is doing event handling (so we can - * piggyback onto them). It is also equipped to handle a combination of - * the two, for example, another thread is doing event handling, but for - * whatever reason it stops doing so before our condition is met, so we take - * over the event handling. - * - * Four functions were introduced in the above pseudo-code. Their importance - * should be apparent from the code shown above. - * -# libusb_try_lock_events() is a non-blocking function which attempts - * to acquire the events lock but returns a failure code if it is contended. - * -# libusb_event_handling_ok() checks that libusb is still happy for your - * thread to be performing event handling. Sometimes, libusb needs to - * interrupt the event handler, and this is how you can check if you have - * been interrupted. If this function returns 0, the correct behaviour is - * for you to give up the event handling lock, and then to repeat the cycle. - * The following libusb_try_lock_events() will fail, so you will become an - * events waiter. For more information on this, read \ref fullstory below. - * -# libusb_handle_events_locked() is a variant of - * libusb_handle_events_timeout() that you can call while holding the - * events lock. libusb_handle_events_timeout() itself implements similar - * logic to the above, so be sure not to call it when you are - * "working behind libusb's back", as is the case here. - * -# libusb_event_handler_active() determines if someone is currently - * holding the events lock - * - * You might be wondering why there is no function to wake up all threads - * blocked on libusb_wait_for_event(). This is because libusb can do this - * internally: it will wake up all such threads when someone calls - * libusb_unlock_events() or when a transfer completes (at the point after its - * callback has returned). - * - * \subsection fullstory The full story - * - * The above explanation should be enough to get you going, but if you're - * really thinking through the issues then you may be left with some more - * questions regarding libusb's internals. If you're curious, read on, and if - * not, skip to the next section to avoid confusing yourself! - * - * The immediate question that may spring to mind is: what if one thread - * modifies the set of file descriptors that need to be polled while another - * thread is doing event handling? - * - * There are 2 situations in which this may happen. - * -# libusb_open() will add another file descriptor to the poll set, - * therefore it is desirable to interrupt the event handler so that it - * restarts, picking up the new descriptor. - * -# libusb_close() will remove a file descriptor from the poll set. There - * are all kinds of race conditions that could arise here, so it is - * important that nobody is doing event handling at this time. - * - * libusb handles these issues internally, so application developers do not - * have to stop their event handlers while opening/closing devices. Here's how - * it works, focusing on the libusb_close() situation first: - * - * -# During initialization, libusb opens an internal pipe, and it adds the read - * end of this pipe to the set of file descriptors to be polled. - * -# During libusb_close(), libusb writes some dummy data on this control pipe. - * This immediately interrupts the event handler. libusb also records - * internally that it is trying to interrupt event handlers for this - * high-priority event. - * -# At this point, some of the functions described above start behaving - * differently: - * - libusb_event_handling_ok() starts returning 1, indicating that it is NOT - * OK for event handling to continue. - * - libusb_try_lock_events() starts returning 1, indicating that another - * thread holds the event handling lock, even if the lock is uncontended. - * - libusb_event_handler_active() starts returning 1, indicating that - * another thread is doing event handling, even if that is not true. - * -# The above changes in behaviour result in the event handler stopping and - * giving up the events lock very quickly, giving the high-priority - * libusb_close() operation a "free ride" to acquire the events lock. All - * threads that are competing to do event handling become event waiters. - * -# With the events lock held inside libusb_close(), libusb can safely remove - * a file descriptor from the poll set, in the safety of knowledge that - * nobody is polling those descriptors or trying to access the poll set. - * -# After obtaining the events lock, the close operation completes very - * quickly (usually a matter of milliseconds) and then immediately releases - * the events lock. - * -# At the same time, the behaviour of libusb_event_handling_ok() and friends - * reverts to the original, documented behaviour. - * -# The release of the events lock causes the threads that are waiting for - * events to be woken up and to start competing to become event handlers - * again. One of them will succeed; it will then re-obtain the list of poll - * descriptors, and USB I/O will then continue as normal. - * - * libusb_open() is similar, and is actually a more simplistic case. Upon a - * call to libusb_open(): - * - * -# The device is opened and a file descriptor is added to the poll set. - * -# libusb sends some dummy data on the control pipe, and records that it - * is trying to modify the poll descriptor set. - * -# The event handler is interrupted, and the same behaviour change as for - * libusb_close() takes effect, causing all event handling threads to become - * event waiters. - * -# The libusb_open() implementation takes its free ride to the events lock. - * -# Happy that it has successfully paused the events handler, libusb_open() - * releases the events lock. - * -# The event waiter threads are all woken up and compete to become event - * handlers again. The one that succeeds will obtain the list of poll - * descriptors again, which will include the addition of the new device. - * - * \subsection concl Closing remarks - * - * The above may seem a little complicated, but hopefully I have made it clear - * why such complications are necessary. Also, do not forget that this only - * applies to applications that take libusb's file descriptors and integrate - * them into their own polling loops. - * - * You may decide that it is OK for your multi-threaded application to ignore - * some of the rules and locks detailed above, because you don't think that - * two threads can ever be polling the descriptors at the same time. If that - * is the case, then that's good news for you because you don't have to worry. - * But be careful here; remember that the synchronous I/O functions do event - * handling internally. If you have one thread doing event handling in a loop - * (without implementing the rules and locking semantics documented above) - * and another trying to send a synchronous USB transfer, you will end up with - * two threads monitoring the same descriptors, and the above-described - * undesirable behaviour occuring. The solution is for your polling thread to - * play by the rules; the synchronous I/O functions do so, and this will result - * in them getting along in perfect harmony. - * - * If you do have a dedicated thread doing event handling, it is perfectly - * legal for it to take the event handling lock for long periods of time. Any - * synchronous I/O functions you call from other threads will transparently - * fall back to the "event waiters" mechanism detailed above. The only - * consideration that your event handling thread must apply is the one related - * to libusb_event_handling_ok(): you must call this before every poll(), and - * give up the events lock if instructed. - */ - -int usbi_io_init(struct libusb_context *ctx) -{ - int r; - - usbi_mutex_init(&ctx->flying_transfers_lock, NULL); - usbi_mutex_init(&ctx->pollfds_lock, NULL); - usbi_mutex_init(&ctx->pollfd_modify_lock, NULL); - usbi_mutex_init(&ctx->events_lock, NULL); - usbi_mutex_init(&ctx->event_waiters_lock, NULL); - usbi_cond_init(&ctx->event_waiters_cond, NULL); - list_init(&ctx->flying_transfers); - list_init(&ctx->pollfds); - - /* FIXME should use an eventfd on kernels that support it */ - r = usbi_pipe(ctx->ctrl_pipe); - if (r < 0) { - r = LIBUSB_ERROR_OTHER; - goto err; - } - - r = usbi_add_pollfd(ctx, ctx->ctrl_pipe[0], POLLIN); - if (r < 0) - goto err_close_pipe; - -#ifdef USBI_TIMERFD_AVAILABLE - ctx->timerfd = timerfd_create(usbi_backend->get_timerfd_clockid(), - TFD_NONBLOCK); - if (ctx->timerfd >= 0) { - usbi_dbg("using timerfd for timeouts"); - r = usbi_add_pollfd(ctx, ctx->timerfd, POLLIN); - if (r < 0) { - usbi_remove_pollfd(ctx, ctx->ctrl_pipe[0]); - close(ctx->timerfd); - goto err_close_pipe; - } - } else { - usbi_dbg("timerfd not available (code %d error %d)", ctx->timerfd, errno); - ctx->timerfd = -1; - } -#endif - - return 0; - -err_close_pipe: - usbi_close(ctx->ctrl_pipe[0]); - usbi_close(ctx->ctrl_pipe[1]); -err: - usbi_mutex_destroy(&ctx->flying_transfers_lock); - usbi_mutex_destroy(&ctx->pollfds_lock); - usbi_mutex_destroy(&ctx->pollfd_modify_lock); - usbi_mutex_destroy(&ctx->events_lock); - usbi_mutex_destroy(&ctx->event_waiters_lock); - usbi_cond_destroy(&ctx->event_waiters_cond); - return r; -} - -void usbi_io_exit(struct libusb_context *ctx) -{ - usbi_remove_pollfd(ctx, ctx->ctrl_pipe[0]); - usbi_close(ctx->ctrl_pipe[0]); - usbi_close(ctx->ctrl_pipe[1]); -#ifdef USBI_TIMERFD_AVAILABLE - if (usbi_using_timerfd(ctx)) { - usbi_remove_pollfd(ctx, ctx->timerfd); - close(ctx->timerfd); - } -#endif - usbi_mutex_destroy(&ctx->flying_transfers_lock); - usbi_mutex_destroy(&ctx->pollfds_lock); - usbi_mutex_destroy(&ctx->pollfd_modify_lock); - usbi_mutex_destroy(&ctx->events_lock); - usbi_mutex_destroy(&ctx->event_waiters_lock); - usbi_cond_destroy(&ctx->event_waiters_cond); -} - -static int calculate_timeout(struct usbi_transfer *transfer) -{ - int r; - struct timespec current_time; - unsigned int timeout = - __USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout; - - if (!timeout) - return 0; - - r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, ¤t_time); - if (r < 0) { - usbi_err(ITRANSFER_CTX(transfer), - "failed to read monotonic clock, errno=%d", errno); - return r; - } - - current_time.tv_sec += timeout / 1000; - current_time.tv_nsec += (timeout % 1000) * 1000000; - - if (current_time.tv_nsec > 1000000000) { - current_time.tv_nsec -= 1000000000; - current_time.tv_sec++; - } - - TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time); - return 0; -} - -/* add a transfer to the (timeout-sorted) active transfers list. - * returns 1 if the transfer has a timeout and it is the timeout next to - * expire */ -static int add_to_flying_list(struct usbi_transfer *transfer) -{ - struct usbi_transfer *cur; - struct timeval *timeout = &transfer->timeout; - struct libusb_context *ctx = ITRANSFER_CTX(transfer); - int r = 0; - int first = 1; - - usbi_mutex_lock(&ctx->flying_transfers_lock); - - /* if we have no other flying transfers, start the list with this one */ - if (list_empty(&ctx->flying_transfers)) { - list_add(&transfer->list, &ctx->flying_transfers); - if (timerisset(timeout)) - r = 1; - goto out; - } - - /* if we have infinite timeout, append to end of list */ - if (!timerisset(timeout)) { - list_add_tail(&transfer->list, &ctx->flying_transfers); - goto out; - } - - /* otherwise, find appropriate place in list */ - list_for_each_entry(cur, &ctx->flying_transfers, list, struct usbi_transfer) { - /* find first timeout that occurs after the transfer in question */ - struct timeval *cur_tv = &cur->timeout; - - if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) || - (cur_tv->tv_sec == timeout->tv_sec && - cur_tv->tv_usec > timeout->tv_usec)) { - list_add_tail(&transfer->list, &cur->list); - r = first; - goto out; - } - first = 0; - } - - /* otherwise we need to be inserted at the end */ - list_add_tail(&transfer->list, &ctx->flying_transfers); -out: - usbi_mutex_unlock(&ctx->flying_transfers_lock); - return r; -} - -/** \ingroup asyncio - * Allocate a libusb transfer with a specified number of isochronous packet - * descriptors. The returned transfer is pre-initialized for you. When the new - * transfer is no longer needed, it should be freed with - * libusb_free_transfer(). - * - * Transfers intended for non-isochronous endpoints (e.g. control, bulk, - * interrupt) should specify an iso_packets count of zero. - * - * For transfers intended for isochronous endpoints, specify an appropriate - * number of packet descriptors to be allocated as part of the transfer. - * The returned transfer is not specially initialized for isochronous I/O; - * you are still required to set the - * \ref libusb_transfer::num_iso_packets "num_iso_packets" and - * \ref libusb_transfer::type "type" fields accordingly. - * - * It is safe to allocate a transfer with some isochronous packets and then - * use it on a non-isochronous endpoint. If you do this, ensure that at time - * of submission, num_iso_packets is 0 and that type is set appropriately. - * - * \param iso_packets number of isochronous packet descriptors to allocate - * \returns a newly allocated transfer, or NULL on error - */ -DEFAULT_VISIBILITY -struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer( - int iso_packets) -{ - size_t os_alloc_size = usbi_backend->transfer_priv_size - + (usbi_backend->add_iso_packet_size * iso_packets); - size_t alloc_size = sizeof(struct usbi_transfer) - + sizeof(struct libusb_transfer) - + (sizeof(struct libusb_iso_packet_descriptor) * iso_packets) - + os_alloc_size; - struct usbi_transfer *itransfer = malloc(alloc_size); - if (!itransfer) - return NULL; - - memset(itransfer, 0, alloc_size); - itransfer->num_iso_packets = iso_packets; - usbi_mutex_init(&itransfer->lock, NULL); - return __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); -} - -/** \ingroup asyncio - * Free a transfer structure. This should be called for all transfers - * allocated with libusb_alloc_transfer(). - * - * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER - * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is - * non-NULL, this function will also free the transfer buffer using the - * standard system memory allocator (e.g. free()). - * - * It is legal to call this function with a NULL transfer. In this case, - * the function will simply return safely. - * - * It is not legal to free an active transfer (one which has been submitted - * and has not yet completed). - * - * \param transfer the transfer to free - */ -void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer) -{ - struct usbi_transfer *itransfer; - if (!transfer) - return; - - if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer) - free(transfer->buffer); - - itransfer = __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); - usbi_mutex_destroy(&itransfer->lock); - free(itransfer); -} - -/** \ingroup asyncio - * Submit a transfer. This function will fire off the USB transfer and then - * return immediately. - * - * \param transfer the transfer to submit - * \returns 0 on success - * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected - * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted. - * \returns another LIBUSB_ERROR code on other failure - */ -int API_EXPORTED libusb_submit_transfer(struct libusb_transfer *transfer) -{ - struct libusb_context *ctx = TRANSFER_CTX(transfer); - struct usbi_transfer *itransfer = - __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); - int r; - int first; - - usbi_mutex_lock(&itransfer->lock); - itransfer->transferred = 0; - itransfer->flags = 0; - r = calculate_timeout(itransfer); - if (r < 0) { - r = LIBUSB_ERROR_OTHER; - goto out; - } - - first = add_to_flying_list(itransfer); - r = usbi_backend->submit_transfer(itransfer); - if (r) { - usbi_mutex_lock(&ctx->flying_transfers_lock); - list_del(&itransfer->list); - usbi_mutex_unlock(&ctx->flying_transfers_lock); - } -#ifdef USBI_TIMERFD_AVAILABLE - else if (first && usbi_using_timerfd(ctx)) { - /* if this transfer has the lowest timeout of all active transfers, - * rearm the timerfd with this transfer's timeout */ - const struct itimerspec it = { {0, 0}, - { itransfer->timeout.tv_sec, itransfer->timeout.tv_usec * 1000 } }; - usbi_dbg("arm timerfd for timeout in %dms (first in line)", transfer->timeout); - r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL); - if (r < 0) - r = LIBUSB_ERROR_OTHER; - } -#endif - -out: - usbi_mutex_unlock(&itransfer->lock); - return r; -} - -/** \ingroup asyncio - * Asynchronously cancel a previously submitted transfer. - * This function returns immediately, but this does not indicate cancellation - * is complete. Your callback function will be invoked at some later time - * with a transfer status of - * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED - * "LIBUSB_TRANSFER_CANCELLED." - * - * \param transfer the transfer to cancel - * \returns 0 on success - * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is already complete or - * cancelled. - * \returns a LIBUSB_ERROR code on failure - */ -int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer) -{ - struct usbi_transfer *itransfer = - __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); - int r; - - usbi_dbg(""); - usbi_mutex_lock(&itransfer->lock); - r = usbi_backend->cancel_transfer(itransfer); - if (r < 0) - usbi_err(TRANSFER_CTX(transfer), - "cancel transfer failed error %d", r); - usbi_mutex_unlock(&itransfer->lock); - return r; -} - -#ifdef USBI_TIMERFD_AVAILABLE -static int disarm_timerfd(struct libusb_context *ctx) -{ - const struct itimerspec disarm_timer = { { 0, 0 }, { 0, 0 } }; - int r; - - usbi_dbg(""); - r = timerfd_settime(ctx->timerfd, 0, &disarm_timer, NULL); - if (r < 0) - return LIBUSB_ERROR_OTHER; - else - return 0; -} - -/* iterates through the flying transfers, and rearms the timerfd based on the - * next upcoming timeout. - * must be called with flying_list locked. - * returns 0 if there was no timeout to arm, 1 if the next timeout was armed, - * or a LIBUSB_ERROR code on failure. - */ -static int arm_timerfd_for_next_timeout(struct libusb_context *ctx) -{ - struct usbi_transfer *transfer; - - list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) { - struct timeval *cur_tv = &transfer->timeout; - - /* if we've reached transfers of infinite timeout, then we have no - * arming to do */ - if (!timerisset(cur_tv)) - return 0; - - /* act on first transfer that is not already cancelled */ - if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) { - int r; - const struct itimerspec it = { {0, 0}, - { cur_tv->tv_sec, cur_tv->tv_usec * 1000 } }; - usbi_dbg("next timeout originally %dms", __USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout); - r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL); - if (r < 0) - return LIBUSB_ERROR_OTHER; - return 1; - } - } - - return 0; -} -#else -static int disarm_timerfd(struct libusb_context *ctx) -{ - return 0; -} -static int arm_timerfd_for_next_timeout(struct libusb_context *ctx) -{ - return 0; -} -#endif - -/* Handle completion of a transfer (completion might be an error condition). - * This will invoke the user-supplied callback function, which may end up - * freeing the transfer. Therefore you cannot use the transfer structure - * after calling this function, and you should free all backend-specific - * data before calling it. - * Do not call this function with the usbi_transfer lock held. User-specified - * callback functions may attempt to directly resubmit the transfer, which - * will attempt to take the lock. */ -int usbi_handle_transfer_completion(struct usbi_transfer *itransfer, - enum libusb_transfer_status status) -{ - struct libusb_transfer *transfer = - __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); - struct libusb_context *ctx = TRANSFER_CTX(transfer); - uint8_t flags; - int r; - - /* FIXME: could be more intelligent with the timerfd here. we don't need - * to disarm the timerfd if there was no timer running, and we only need - * to rearm the timerfd if the transfer that expired was the one with - * the shortest timeout. */ - - usbi_mutex_lock(&ctx->flying_transfers_lock); - list_del(&itransfer->list); - r = arm_timerfd_for_next_timeout(ctx); - usbi_mutex_unlock(&ctx->flying_transfers_lock); - - if (r < 0) { - return r; - } else if (r == 0) { - r = disarm_timerfd(ctx); - if (r < 0) - return r; - } - - if (status == LIBUSB_TRANSFER_COMPLETED - && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) { - int rqlen = transfer->length; - if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL) - rqlen -= LIBUSB_CONTROL_SETUP_SIZE; - if (rqlen != itransfer->transferred) { - usbi_dbg("interpreting short transfer as error"); - status = LIBUSB_TRANSFER_ERROR; - } - } - - flags = transfer->flags; - transfer->status = status; - transfer->actual_length = itransfer->transferred; - if (transfer->callback) - transfer->callback(transfer); - /* transfer might have been freed by the above call, do not use from - * this point. */ - if (flags & LIBUSB_TRANSFER_FREE_TRANSFER) - libusb_free_transfer(transfer); - usbi_mutex_lock(&ctx->event_waiters_lock); - usbi_cond_broadcast(&ctx->event_waiters_cond); - usbi_mutex_unlock(&ctx->event_waiters_lock); - return 0; -} - -/* Similar to usbi_handle_transfer_completion() but exclusively for transfers - * that were asynchronously cancelled. The same concerns w.r.t. freeing of - * transfers exist here. - * Do not call this function with the usbi_transfer lock held. User-specified - * callback functions may attempt to directly resubmit the transfer, which - * will attempt to take the lock. */ -int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer) -{ - /* if the URB was cancelled due to timeout, report timeout to the user */ - if (transfer->flags & USBI_TRANSFER_TIMED_OUT) { - usbi_dbg("detected timeout cancellation"); - return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT); - } - - /* otherwise its a normal async cancel */ - return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED); -} - -/** \ingroup poll - * Attempt to acquire the event handling lock. This lock is used to ensure that - * only one thread is monitoring libusb event sources at any one time. - * - * You only need to use this lock if you are developing an application - * which calls poll() or select() on libusb's file descriptors directly. - * If you stick to libusb's event handling loop functions (e.g. - * libusb_handle_events()) then you do not need to be concerned with this - * locking. - * - * While holding this lock, you are trusted to actually be handling events. - * If you are no longer handling events, you must call libusb_unlock_events() - * as soon as possible. - * - * \param ctx the context to operate on, or NULL for the default context - * \returns 0 if the lock was obtained successfully - * \returns 1 if the lock was not obtained (i.e. another thread holds the lock) - * \see \ref mtasync - */ -int API_EXPORTED libusb_try_lock_events(libusb_context *ctx) -{ - int r; - USBI_GET_CONTEXT(ctx); - - /* is someone else waiting to modify poll fds? if so, don't let this thread - * start event handling */ - usbi_mutex_lock(&ctx->pollfd_modify_lock); - r = ctx->pollfd_modify; - usbi_mutex_unlock(&ctx->pollfd_modify_lock); - if (r) { - usbi_dbg("someone else is modifying poll fds"); - return 1; - } - - r = usbi_mutex_trylock(&ctx->events_lock); - if (r) - return 1; - - ctx->event_handler_active = 1; - return 0; -} - -/** \ingroup poll - * Acquire the event handling lock, blocking until successful acquisition if - * it is contended. This lock is used to ensure that only one thread is - * monitoring libusb event sources at any one time. - * - * You only need to use this lock if you are developing an application - * which calls poll() or select() on libusb's file descriptors directly. - * If you stick to libusb's event handling loop functions (e.g. - * libusb_handle_events()) then you do not need to be concerned with this - * locking. - * - * While holding this lock, you are trusted to actually be handling events. - * If you are no longer handling events, you must call libusb_unlock_events() - * as soon as possible. - * - * \param ctx the context to operate on, or NULL for the default context - * \see \ref mtasync - */ -void API_EXPORTED libusb_lock_events(libusb_context *ctx) -{ - USBI_GET_CONTEXT(ctx); - usbi_mutex_lock(&ctx->events_lock); - ctx->event_handler_active = 1; -} - -/** \ingroup poll - * Release the lock previously acquired with libusb_try_lock_events() or - * libusb_lock_events(). Releasing this lock will wake up any threads blocked - * on libusb_wait_for_event(). - * - * \param ctx the context to operate on, or NULL for the default context - * \see \ref mtasync - */ -void API_EXPORTED libusb_unlock_events(libusb_context *ctx) -{ - USBI_GET_CONTEXT(ctx); - ctx->event_handler_active = 0; - usbi_mutex_unlock(&ctx->events_lock); - - /* FIXME: perhaps we should be a bit more efficient by not broadcasting - * the availability of the events lock when we are modifying pollfds - * (check ctx->pollfd_modify)? */ - usbi_mutex_lock(&ctx->event_waiters_lock); - usbi_cond_broadcast(&ctx->event_waiters_cond); - usbi_mutex_unlock(&ctx->event_waiters_lock); -} - -/** \ingroup poll - * Determine if it is still OK for this thread to be doing event handling. - * - * Sometimes, libusb needs to temporarily pause all event handlers, and this - * is the function you should use before polling file descriptors to see if - * this is the case. - * - * If this function instructs your thread to give up the events lock, you - * should just continue the usual logic that is documented in \ref mtasync. - * On the next iteration, your thread will fail to obtain the events lock, - * and will hence become an event waiter. - * - * This function should be called while the events lock is held: you don't - * need to worry about the results of this function if your thread is not - * the current event handler. - * - * \param ctx the context to operate on, or NULL for the default context - * \returns 1 if event handling can start or continue - * \returns 0 if this thread must give up the events lock - * \see \ref fullstory "Multi-threaded I/O: the full story" - */ -int API_EXPORTED libusb_event_handling_ok(libusb_context *ctx) -{ - int r; - USBI_GET_CONTEXT(ctx); - - /* is someone else waiting to modify poll fds? if so, don't let this thread - * continue event handling */ - usbi_mutex_lock(&ctx->pollfd_modify_lock); - r = ctx->pollfd_modify; - usbi_mutex_unlock(&ctx->pollfd_modify_lock); - if (r) { - usbi_dbg("someone else is modifying poll fds"); - return 0; - } - - return 1; -} - - -/** \ingroup poll - * Determine if an active thread is handling events (i.e. if anyone is holding - * the event handling lock). - * - * \param ctx the context to operate on, or NULL for the default context - * \returns 1 if a thread is handling events - * \returns 0 if there are no threads currently handling events - * \see \ref mtasync - */ -int API_EXPORTED libusb_event_handler_active(libusb_context *ctx) -{ - int r; - USBI_GET_CONTEXT(ctx); - - /* is someone else waiting to modify poll fds? if so, don't let this thread - * start event handling -- indicate that event handling is happening */ - usbi_mutex_lock(&ctx->pollfd_modify_lock); - r = ctx->pollfd_modify; - usbi_mutex_unlock(&ctx->pollfd_modify_lock); - if (r) { - usbi_dbg("someone else is modifying poll fds"); - return 1; - } - - return ctx->event_handler_active; -} - -/** \ingroup poll - * Acquire the event waiters lock. This lock is designed to be obtained under - * the situation where you want to be aware when events are completed, but - * some other thread is event handling so calling libusb_handle_events() is not - * allowed. - * - * You then obtain this lock, re-check that another thread is still handling - * events, then call libusb_wait_for_event(). - * - * You only need to use this lock if you are developing an application - * which calls poll() or select() on libusb's file descriptors directly, - * <b>and</b> may potentially be handling events from 2 threads simultaenously. - * If you stick to libusb's event handling loop functions (e.g. - * libusb_handle_events()) then you do not need to be concerned with this - * locking. - * - * \param ctx the context to operate on, or NULL for the default context - * \see \ref mtasync - */ -void API_EXPORTED libusb_lock_event_waiters(libusb_context *ctx) -{ - USBI_GET_CONTEXT(ctx); - usbi_mutex_lock(&ctx->event_waiters_lock); -} - -/** \ingroup poll - * Release the event waiters lock. - * \param ctx the context to operate on, or NULL for the default context - * \see \ref mtasync - */ -void API_EXPORTED libusb_unlock_event_waiters(libusb_context *ctx) -{ - USBI_GET_CONTEXT(ctx); - usbi_mutex_unlock(&ctx->event_waiters_lock); -} - -/** \ingroup poll - * Wait for another thread to signal completion of an event. Must be called - * with the event waiters lock held, see libusb_lock_event_waiters(). - * - * This function will block until any of the following conditions are met: - * -# The timeout expires - * -# A transfer completes - * -# A thread releases the event handling lock through libusb_unlock_events() - * - * Condition 1 is obvious. Condition 2 unblocks your thread <em>after</em> - * the callback for the transfer has completed. Condition 3 is important - * because it means that the thread that was previously handling events is no - * longer doing so, so if any events are to complete, another thread needs to - * step up and start event handling. - * - * This function releases the event waiters lock before putting your thread - * to sleep, and reacquires the lock as it is being woken up. - * - * \param ctx the context to operate on, or NULL for the default context - * \param tv maximum timeout for this blocking function. A NULL value - * indicates unlimited timeout. - * \returns 0 after a transfer completes or another thread stops event handling - * \returns 1 if the timeout expired - * \see \ref mtasync - */ -int API_EXPORTED libusb_wait_for_event(libusb_context *ctx, struct timeval *tv) -{ - struct timespec timeout; - int r; - - USBI_GET_CONTEXT(ctx); - if (tv == NULL) { - usbi_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock); - return 0; - } - - r = usbi_backend->clock_gettime(USBI_CLOCK_REALTIME, &timeout); - if (r < 0) { - usbi_err(ctx, "failed to read realtime clock, error %d", errno); - return LIBUSB_ERROR_OTHER; - } - - timeout.tv_sec += tv->tv_sec; - timeout.tv_nsec += tv->tv_usec * 1000; - if (timeout.tv_nsec > 1000000000) { - timeout.tv_nsec -= 1000000000; - timeout.tv_sec++; - } - - r = usbi_cond_timedwait(&ctx->event_waiters_cond, - &ctx->event_waiters_lock, &timeout); - return (r == ETIMEDOUT); -} - -static void handle_timeout(struct usbi_transfer *itransfer) -{ - struct libusb_transfer *transfer = - __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); - int r; - - itransfer->flags |= USBI_TRANSFER_TIMED_OUT; - r = libusb_cancel_transfer(transfer); - if (r < 0) - usbi_warn(TRANSFER_CTX(transfer), - "async cancel failed %d errno=%d", r, errno); -} - -#ifdef USBI_OS_HANDLES_TIMEOUT -static int handle_timeouts_locked(struct libusb_context *ctx) -{ - return 0; -} -static int handle_timeouts(struct libusb_context *ctx) -{ - return 0; -} -#else -static int handle_timeouts_locked(struct libusb_context *ctx) -{ - int r; - struct timespec systime_ts; - struct timeval systime; - struct usbi_transfer *transfer; - - if (list_empty(&ctx->flying_transfers)) - return 0; - - /* get current time */ - r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &systime_ts); - if (r < 0) - return r; - - TIMESPEC_TO_TIMEVAL(&systime, &systime_ts); - - /* iterate through flying transfers list, finding all transfers that - * have expired timeouts */ - list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) { - struct timeval *cur_tv = &transfer->timeout; - - /* if we've reached transfers of infinite timeout, we're all done */ - if (!timerisset(cur_tv)) - return 0; - - /* ignore timeouts we've already handled */ - if (transfer->flags & USBI_TRANSFER_TIMED_OUT) - continue; - - /* if transfer has non-expired timeout, nothing more to do */ - if ((cur_tv->tv_sec > systime.tv_sec) || - (cur_tv->tv_sec == systime.tv_sec && - cur_tv->tv_usec > systime.tv_usec)) - return 0; - - /* otherwise, we've got an expired timeout to handle */ - handle_timeout(transfer); - } - return 0; -} - -static int handle_timeouts(struct libusb_context *ctx) -{ - int r; - USBI_GET_CONTEXT(ctx); - usbi_mutex_lock(&ctx->flying_transfers_lock); - r = handle_timeouts_locked(ctx); - usbi_mutex_unlock(&ctx->flying_transfers_lock); - return r; -} -#endif - -#ifdef USBI_TIMERFD_AVAILABLE -static int handle_timerfd_trigger(struct libusb_context *ctx) -{ - int r; - - r = disarm_timerfd(ctx); - if (r < 0) - return r; - - usbi_mutex_lock(&ctx->flying_transfers_lock); - - /* process the timeout that just happened */ - r = handle_timeouts_locked(ctx); - if (r < 0) - goto out; - - /* arm for next timeout*/ - r = arm_timerfd_for_next_timeout(ctx); - -out: - usbi_mutex_unlock(&ctx->flying_transfers_lock); - return r; -} -#endif - -/* do the actual event handling. assumes that no other thread is concurrently - * doing the same thing. */ -static int handle_events(struct libusb_context *ctx, struct timeval *tv) -{ - int r; - struct usbi_pollfd *ipollfd; - nfds_t nfds = 0; - struct pollfd *fds; - int i = -1; - int timeout_ms; - - usbi_mutex_lock(&ctx->pollfds_lock); - list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) - nfds++; - - /* TODO: malloc when number of fd's changes, not on every poll */ - fds = malloc(sizeof(*fds) * nfds); - if (!fds) { - usbi_mutex_unlock(&ctx->pollfds_lock); - return LIBUSB_ERROR_NO_MEM; - } - - list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) { - struct libusb_pollfd *pollfd = &ipollfd->pollfd; - int fd = pollfd->fd; - i++; - fds[i].fd = fd; - fds[i].events = pollfd->events; - fds[i].revents = 0; - } - usbi_mutex_unlock(&ctx->pollfds_lock); - - timeout_ms = (tv->tv_sec * 1000) + (tv->tv_usec / 1000); - - /* round up to next millisecond */ - if (tv->tv_usec % 1000) - timeout_ms++; - - usbi_dbg("poll() %d fds with timeout in %dms", nfds, timeout_ms); - r = usbi_poll(fds, nfds, timeout_ms); - usbi_dbg("poll() returned %d", r); - if (r == 0) { - free(fds); - return handle_timeouts(ctx); - } else if (r == -1 && errno == EINTR) { - free(fds); - return LIBUSB_ERROR_INTERRUPTED; - } else if (r < 0) { - free(fds); - usbi_err(ctx, "poll failed %d err=%d\n", r, errno); - return LIBUSB_ERROR_IO; - } - - /* fd[0] is always the ctrl pipe */ - if (fds[0].revents) { - /* another thread wanted to interrupt event handling, and it succeeded! - * handle any other events that cropped up at the same time, and - * simply return */ - usbi_dbg("caught a fish on the control pipe"); - - if (r == 1) { - r = 0; - goto handled; - } else { - /* prevent OS backend from trying to handle events on ctrl pipe */ - fds[0].revents = 0; - r--; - } - } - -#ifdef USBI_TIMERFD_AVAILABLE - /* on timerfd configurations, fds[1] is the timerfd */ - if (usbi_using_timerfd(ctx) && fds[1].revents) { - /* timerfd indicates that a timeout has expired */ - int ret; - usbi_dbg("timerfd triggered"); - - ret = handle_timerfd_trigger(ctx); - if (ret < 0) { - /* return error code */ - r = ret; - goto handled; - } else if (r == 1) { - /* no more active file descriptors, nothing more to do */ - r = 0; - goto handled; - } else { - /* more events pending... - * prevent OS backend from trying to handle events on timerfd */ - fds[1].revents = 0; - r--; - } - } -#endif - - r = usbi_backend->handle_events(ctx, fds, nfds, r); - if (r) - usbi_err(ctx, "backend handle_events failed with error %d", r); - -handled: - free(fds); - return r; -} - -/* returns the smallest of: - * 1. timeout of next URB - * 2. user-supplied timeout - * returns 1 if there is an already-expired timeout, otherwise returns 0 - * and populates out - */ -static int get_next_timeout(libusb_context *ctx, struct timeval *tv, - struct timeval *out) -{ - struct timeval timeout; - int r = libusb_get_next_timeout(ctx, &timeout); - if (r) { - /* timeout already expired? */ - if (!timerisset(&timeout)) - return 1; - - /* choose the smallest of next URB timeout or user specified timeout */ - if (timercmp(&timeout, tv, <)) - *out = timeout; - else - *out = *tv; - } else { - *out = *tv; - } - return 0; -} - -/** \ingroup poll - * Handle any pending events. - * - * libusb determines "pending events" by checking if any timeouts have expired - * and by checking the set of file descriptors for activity. - * - * If a zero timeval is passed, this function will handle any already-pending - * events and then immediately return in non-blocking style. - * - * If a non-zero timeval is passed and no events are currently pending, this - * function will block waiting for events to handle up until the specified - * timeout. If an event arrives or a signal is raised, this function will - * return early. - * - * \param ctx the context to operate on, or NULL for the default context - * \param tv the maximum time to block waiting for events, or zero for - * non-blocking mode - * \returns 0 on success, or a LIBUSB_ERROR code on failure - */ -int API_EXPORTED libusb_handle_events_timeout_check(libusb_context *ctx, - struct timeval *tv, int *completed) -{ - int r; - struct timeval poll_timeout; - - USBI_GET_CONTEXT(ctx); - r = get_next_timeout(ctx, tv, &poll_timeout); - if (r) { - /* timeout already expired */ - return handle_timeouts(ctx); - } - -retry: - if (libusb_try_lock_events(ctx) == 0) { - r = 0; - if (completed == NULL || !*completed) { - /* we obtained the event lock: do our own event handling */ - usbi_dbg("doing our own event handling"); - r = handle_events(ctx, &poll_timeout); - } - libusb_unlock_events(ctx); - return r; - } - - /* another thread is doing event handling. wait for pthread events that - * notify event completion. */ - libusb_lock_event_waiters(ctx); - - if (completed == NULL || !*completed) { - if (!libusb_event_handler_active(ctx)) { - /* we hit a race: whoever was event handling earlier finished in the - * time it took us to reach this point. try the cycle again. */ - libusb_unlock_event_waiters(ctx); - usbi_dbg("event handler was active but went away, retrying"); - goto retry; - } - - usbi_dbg("another thread is doing event handling, wait for notification"); - r = libusb_wait_for_event(ctx, &poll_timeout); - } - libusb_unlock_event_waiters(ctx); - - if (r < 0) - return r; - else if (r == 1) - return handle_timeouts(ctx); - else - return 0; -} - -int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx, - struct timeval *tv) -{ - return libusb_handle_events_timeout_check(ctx, tv, NULL); -} - -int API_EXPORTED libusb_handle_events_check(libusb_context *ctx, - int *completed) -{ - struct timeval tv; - tv.tv_sec = 60; - tv.tv_usec = 0; - return libusb_handle_events_timeout_check(ctx, &tv, completed); -} - -/** \ingroup poll - * Handle any pending events in blocking mode. There is currently a timeout - * hardcoded at 60 seconds but we plan to make it unlimited in future. For - * finer control over whether this function is blocking or non-blocking, or - * for control over the timeout, use libusb_handle_events_timeout() instead. - * - * \param ctx the context to operate on, or NULL for the default context - * \returns 0 on success, or a LIBUSB_ERROR code on failure - */ -int API_EXPORTED libusb_handle_events(libusb_context *ctx) -{ - struct timeval tv; - tv.tv_sec = 60; - tv.tv_usec = 0; - return libusb_handle_events_timeout_check(ctx, &tv, NULL); -} - -/** \ingroup poll - * Handle any pending events by polling file descriptors, without checking if - * any other threads are already doing so. Must be called with the event lock - * held, see libusb_lock_events(). - * - * This function is designed to be called under the situation where you have - * taken the event lock and are calling poll()/select() directly on libusb's - * file descriptors (as opposed to using libusb_handle_events() or similar). - * You detect events on libusb's descriptors, so you then call this function - * with a zero timeout value (while still holding the event lock). - * - * \param ctx the context to operate on, or NULL for the default context - * \param tv the maximum time to block waiting for events, or zero for - * non-blocking mode - * \returns 0 on success, or a LIBUSB_ERROR code on failure - * \see \ref mtasync - */ -int API_EXPORTED libusb_handle_events_locked(libusb_context *ctx, - struct timeval *tv) -{ - int r; - struct timeval poll_timeout; - - USBI_GET_CONTEXT(ctx); - r = get_next_timeout(ctx, tv, &poll_timeout); - if (r) { - /* timeout already expired */ - return handle_timeouts(ctx); - } - - return handle_events(ctx, &poll_timeout); -} - -/** \ingroup poll - * Determines whether your application must apply special timing considerations - * when monitoring libusb's file descriptors. - * - * This function is only useful for applications which retrieve and poll - * libusb's file descriptors in their own main loop (\ref pollmain). - * - * Ordinarily, libusb's event handler needs to be called into at specific - * moments in time (in addition to times when there is activity on the file - * descriptor set). The usual approach is to use libusb_get_next_timeout() - * to learn about when the next timeout occurs, and to adjust your - * poll()/select() timeout accordingly so that you can make a call into the - * library at that time. - * - * Some platforms supported by libusb do not come with this baggage - any - * events relevant to timing will be represented by activity on the file - * descriptor set, and libusb_get_next_timeout() will always return 0. - * This function allows you to detect whether you are running on such a - * platform. - * - * Since v1.0.5. - * - * \param ctx the context to operate on, or NULL for the default context - * \returns 0 if you must call into libusb at times determined by - * libusb_get_next_timeout(), or 1 if all timeout events are handled internally - * or through regular activity on the file descriptors. - * \see \ref pollmain "Polling libusb file descriptors for event handling" - */ -int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx) -{ -#if defined(USBI_OS_HANDLES_TIMEOUT) - return 1; -#elif defined(USBI_TIMERFD_AVAILABLE) - USBI_GET_CONTEXT(ctx); - return usbi_using_timerfd(ctx); -#else - return 0; -#endif -} - -/** \ingroup poll - * Determine the next internal timeout that libusb needs to handle. You only - * need to use this function if you are calling poll() or select() or similar - * on libusb's file descriptors yourself - you do not need to use it if you - * are calling libusb_handle_events() or a variant directly. - * - * You should call this function in your main loop in order to determine how - * long to wait for select() or poll() to return results. libusb needs to be - * called into at this timeout, so you should use it as an upper bound on - * your select() or poll() call. - * - * When the timeout has expired, call into libusb_handle_events_timeout() - * (perhaps in non-blocking mode) so that libusb can handle the timeout. - * - * This function may return 1 (success) and an all-zero timeval. If this is - * the case, it indicates that libusb has a timeout that has already expired - * so you should call libusb_handle_events_timeout() or similar immediately. - * A return code of 0 indicates that there are no pending timeouts. - * - * On some platforms, this function will always returns 0 (no pending - * timeouts). See \ref polltime. - * - * \param ctx the context to operate on, or NULL for the default context - * \param tv output location for a relative time against the current - * clock in which libusb must be called into in order to process timeout events - * \returns 0 if there are no pending timeouts, 1 if a timeout was returned, - * or LIBUSB_ERROR_OTHER on failure - */ -int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx, - struct timeval *tv) -{ -#ifndef USBI_OS_HANDLES_TIMEOUT - struct usbi_transfer *transfer; - struct timespec cur_ts; - struct timeval cur_tv; - struct timeval *next_timeout; - int r; - int found = 0; - - USBI_GET_CONTEXT(ctx); - if (usbi_using_timerfd(ctx)) - return 0; - - usbi_mutex_lock(&ctx->flying_transfers_lock); - if (list_empty(&ctx->flying_transfers)) { - usbi_mutex_unlock(&ctx->flying_transfers_lock); - usbi_dbg("no URBs, no timeout!"); - return 0; - } - - /* find next transfer which hasn't already been processed as timed out */ - list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) { - if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) { - found = 1; - break; - } - } - usbi_mutex_unlock(&ctx->flying_transfers_lock); - - if (!found) { - usbi_dbg("all URBs have already been processed for timeouts"); - return 0; - } - - next_timeout = &transfer->timeout; - - /* no timeout for next transfer */ - if (!timerisset(next_timeout)) { - usbi_dbg("no URBs with timeouts, no timeout!"); - return 0; - } - - r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &cur_ts); - if (r < 0) { - usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno); - return LIBUSB_ERROR_OTHER; - } - TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts); - - if (!timercmp(&cur_tv, next_timeout, <)) { - usbi_dbg("first timeout already expired"); - timerclear(tv); - } else { - timersub(next_timeout, &cur_tv, tv); - usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec); - } - - return 1; -#else - return 0; -#endif -} - -/** \ingroup poll - * Register notification functions for file descriptor additions/removals. - * These functions will be invoked for every new or removed file descriptor - * that libusb uses as an event source. - * - * To remove notifiers, pass NULL values for the function pointers. - * - * Note that file descriptors may have been added even before you register - * these notifiers (e.g. at libusb_init() time). - * - * Additionally, note that the removal notifier may be called during - * libusb_exit() (e.g. when it is closing file descriptors that were opened - * and added to the poll set at libusb_init() time). If you don't want this, - * remove the notifiers immediately before calling libusb_exit(). - * - * \param ctx the context to operate on, or NULL for the default context - * \param added_cb pointer to function for addition notifications - * \param removed_cb pointer to function for removal notifications - * \param user_data User data to be passed back to callbacks (useful for - * passing context information) - */ -void API_EXPORTED libusb_set_pollfd_notifiers(libusb_context *ctx, - libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb, - void *user_data) -{ - USBI_GET_CONTEXT(ctx); - ctx->fd_added_cb = added_cb; - ctx->fd_removed_cb = removed_cb; - ctx->fd_cb_user_data = user_data; -} - -/* Add a file descriptor to the list of file descriptors to be monitored. - * events should be specified as a bitmask of events passed to poll(), e.g. - * POLLIN and/or POLLOUT. */ -int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events) -{ - struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd)); - if (!ipollfd) - return LIBUSB_ERROR_NO_MEM; - - usbi_dbg("add fd %d events %d", fd, events); - ipollfd->pollfd.fd = fd; - ipollfd->pollfd.events = events; - usbi_mutex_lock(&ctx->pollfds_lock); - list_add_tail(&ipollfd->list, &ctx->pollfds); - usbi_mutex_unlock(&ctx->pollfds_lock); - - if (ctx->fd_added_cb) - ctx->fd_added_cb(fd, events, ctx->fd_cb_user_data); - return 0; -} - -/* Remove a file descriptor from the list of file descriptors to be polled. */ -void usbi_remove_pollfd(struct libusb_context *ctx, int fd) -{ - struct usbi_pollfd *ipollfd; - int found = 0; - - usbi_dbg("remove fd %d", fd); - usbi_mutex_lock(&ctx->pollfds_lock); - list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) - if (ipollfd->pollfd.fd == fd) { - found = 1; - break; - } - - if (!found) { - usbi_dbg("couldn't find fd %d to remove", fd); - usbi_mutex_unlock(&ctx->pollfds_lock); - return; - } - - list_del(&ipollfd->list); - usbi_mutex_unlock(&ctx->pollfds_lock); - free(ipollfd); - if (ctx->fd_removed_cb) - ctx->fd_removed_cb(fd, ctx->fd_cb_user_data); -} - -/** \ingroup poll - * Retrieve a list of file descriptors that should be polled by your main loop - * as libusb event sources. - * - * The returned list is NULL-terminated and should be freed with free() when - * done. The actual list contents must not be touched. - * - * As file descriptors are a Unix-specific concept, this function is not - * available on Windows and will always return NULL. - * - * \param ctx the context to operate on, or NULL for the default context - * \returns a NULL-terminated list of libusb_pollfd structures - * \returns NULL on error - * \returns NULL on platforms where the functionality is not available - */ -DEFAULT_VISIBILITY -const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds( - libusb_context *ctx) -{ -#ifndef OS_WINDOWS - struct libusb_pollfd **ret = NULL; - struct usbi_pollfd *ipollfd; - size_t i = 0; - size_t cnt = 0; - USBI_GET_CONTEXT(ctx); - - usbi_mutex_lock(&ctx->pollfds_lock); - list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) - cnt++; - - ret = calloc(cnt + 1, sizeof(struct libusb_pollfd *)); - if (!ret) - goto out; - - list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) - ret[i++] = (struct libusb_pollfd *) ipollfd; - ret[cnt] = NULL; - -out: - usbi_mutex_unlock(&ctx->pollfds_lock); - return (const struct libusb_pollfd **) ret; -#else - return NULL; -#endif -} - -/* Backends call this from handle_events to report disconnection of a device. - * The transfers get cancelled appropriately. - */ -void usbi_handle_disconnect(struct libusb_device_handle *handle) -{ - struct usbi_transfer *cur; - struct usbi_transfer *to_cancel; - - usbi_dbg("device %d.%d", - handle->dev->bus_number, handle->dev->device_address); - - /* terminate all pending transfers with the LIBUSB_TRANSFER_NO_DEVICE - * status code. - * - * this is a bit tricky because: - * 1. we can't do transfer completion while holding flying_transfers_lock - * 2. the transfers list can change underneath us - if we were to build a - * list of transfers to complete (while holding look), the situation - * might be different by the time we come to free them - * - * so we resort to a loop-based approach as below - * FIXME: is this still potentially racy? - */ - - while (1) { - usbi_mutex_lock(&HANDLE_CTX(handle)->flying_transfers_lock); - to_cancel = NULL; - list_for_each_entry(cur, &HANDLE_CTX(handle)->flying_transfers, list, struct usbi_transfer) - if (__USBI_TRANSFER_TO_LIBUSB_TRANSFER(cur)->dev_handle == handle) { - to_cancel = cur; - break; - } - usbi_mutex_unlock(&HANDLE_CTX(handle)->flying_transfers_lock); - - if (!to_cancel) - break; - - usbi_backend->clear_transfer_priv(to_cancel); - usbi_handle_transfer_completion(to_cancel, LIBUSB_TRANSFER_NO_DEVICE); - } - -} |