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diff --git a/libusb-1.0/libusb/io.c b/libusb-1.0/libusb/io.c new file mode 100644 index 0000000..d4f6f3d --- /dev/null +++ b/libusb-1.0/libusb/io.c @@ -0,0 +1,2366 @@ +/* + * 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); + } + +} |