/*
- * I/O functions for libusb
- * Copyright (C) 2007-2008 Daniel Drake <dsd@gentoo.org>
- * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * I/O functions for libusbx
+ * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 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
#include <config.h>
#include <errno.h>
-#include <poll.h>
-#include <pthread.h>
#include <signal.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
-#include <sys/select.h>
-#include <sys/time.h>
#include <time.h>
-#include <unistd.h>
-
-#include "libusbi.h"
-/* this is a list of in-flight transfer handles, sorted by timeout expiration.
- * URBs to timeout the soonest are placed at the beginning of the list, URBs
- * that will time out later are placed after, and urbs with infinite timeout
- * are always placed at the very end. */
-static struct list_head flying_transfers;
-static pthread_mutex_t flying_transfers_lock = PTHREAD_MUTEX_INITIALIZER;
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
-/* list of poll fd's */
-static struct list_head pollfds;
+#ifdef USBI_TIMERFD_AVAILABLE
+#include <sys/timerfd.h>
+#endif
-/* user callbacks for pollfd changes */
-static libusb_pollfd_added_cb fd_added_cb = NULL;
-static libusb_pollfd_removed_cb fd_removed_cb = NULL;
+#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
+ * If you're using libusbx 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
+ * libusbx 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.
* 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
+ * libusbx 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.
* 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);
+int actual_length;
+int r = libusb_bulk_transfer(handle, LIBUSB_ENDPOINT_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
*
* 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.
* above.
*
* Instead of providing which functions that block until the I/O has complete,
- * libusb's asynchronous interface presents non-blocking functions which
+ * libusbx'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
+ * callback function pointer to this non-blocking function, which libusbx will
* call with the results of the transaction when it has completed.
*
* Transfers which have been submitted through the non-blocking functions
* to use threads.
*
* This added flexibility does come with some complications though:
- * - In the interest of being a lightweight library, libusb does not create
+ * - In the interest of being a lightweight library, libusbx 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
+ * application must call into libusbx from it's main loop when events are ready
+ * to be handled, or you must use some other scheme to allow libusbx to
* undertake whatever work needs to be done.
- * - libusb also needs to be called into at certain fixed points in time in
+ * - libusbx 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
* 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
+ * Internally, libusbx'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.
+ *
+ * libusbx 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, libusbx requires you to supply a
+ * buffer and the maximum number of bytes of data that libusbx 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. libusbx 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. libusbx 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
+ * This page details libusbx'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
*
* \section asyncabstraction Transfer abstraction
*
- * For the asynchronous I/O, libusb implements the concept of a generic
+ * For the asynchronous I/O, libusbx 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.
* \section asynctrf Asynchronous transfers
*
* We can view asynchronous I/O as a 5 step process:
- * -# Allocation
- * -# Filling
- * -# Submission
- * -# Completion handling
- * -# Deallocation
+ * -# <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 libusbx 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
*
* 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, libusbx 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),
* 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.
+ * libusbx 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
* 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
* 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
*
- * As isochronous transfers are more complicated than transfers to
+ * 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::endpoint_type "endpoint_type" to
- * \ref libusb_endpoint_type::LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS
- * "LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS", and set
+ * 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
* 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 endpoint descriptor. FIXME need a helper
- * function to find this.
- * FIXME, write a helper function to set the length for all iso packets in an
- * array
+ * 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
* - 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. FIXME write
- * a helper function to determine this, and flesh this description out a bit
- * more.
+ * 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
+ * transfer may return before libusbx 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.
*
* \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
+ * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusbx 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
+ * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusbx 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
+ * In accordance of the aim of being a lightweight library, libusbx does not
+ * create threads internally. This means that libusbx code does not execute
+ * at any time other than when your application is calling a libusbx function.
+ * However, an asynchronous model requires that libusbx 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
+ * application must call into when libusbx has work do to. This gives libusbx
* 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
+ * when libusbx 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
+ * 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
+ *
+ * The recommended option is to integrate libusbx with your application main
+ * event loop. libusbx 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
+ * libusbx'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
+ * There is one final event handling complication. libusbx 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
+ * this requires that libusbx is called into at or after the timeout so that
+ * the timeout can be handled. So, in addition to considering libusbx's file
+ * descriptors in your main event loop, you must also consider that libusbx
* sometimes needs to be called into at fixed points in time even when there
* is no file descriptor activity.
*
/**
* @defgroup poll Polling and timing
*
- * This page documents libusb's functions for polling events and timing.
+ * This page documents libusbx'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
*
* 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
+ * asynchronous API documentation. In summary, libusbx 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
+ * into libusbx at certain points in time so that pending events can be handled.
+ * In order to know precisely when libusbx needs to be called into, libusbx
* offers you a set of pollable file descriptors and information about when
* the next timeout expires.
*
*
* \section pollsimple The simple option
*
- * If your application revolves solely around libusb and does not need to
+ * If your application revolves solely around libusbx and does not need to
* handle other event sources, you can have a program structure as follows:
\code
-// initialize libusb
+// initialize libusbx
// find and open device
// maybe fire off some initial async I/O
while (user_has_not_requested_exit)
- libusb_handle_events();
+ libusb_handle_events(ctx);
// clean up and exit
\endcode
*
* \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
+ * movements, etc. Through exposing a set of file descriptors, libusbx 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
+ * take a set of file descriptors from libusbx and monitor those too. When you
+ * detect activity on libusbx's file descriptors, you call
* libusb_handle_events_timeout() in non-blocking mode.
*
- * You must also consider the fact that libusb sometimes has to handle events
- * at certain known times which do not generate activity on file descriptors.
- * Your main loop must also consider these times, modify it's poll()/select()
- * timeout accordingly, and track time so that libusb_handle_events_timeout()
- * is called in non-blocking mode when timeouts expire.
+ * What's more, libusbx 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.
+ *
+ * libusbx 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 libusbx indicates,
+ * polling all of them at once.
*
* In pseudo-code, you want something that looks like:
\code
-// initialise libusb
+// initialise libusbx
+
+libusb_get_pollfds(ctx)
+while (user has not requested application exit) {
+ libusb_get_next_timeout(ctx);
+ poll(on libusbx file descriptors plus any other event sources of interest,
+ using a timeout no larger than the value libusbx just suggested)
+ if (poll() indicated activity on libusbx file descriptors)
+ libusb_handle_events_timeout(ctx, &zero_tv);
+ if (time has elapsed to or beyond the libusbx timeout)
+ libusb_handle_events_timeout(ctx, &zero_tv);
+ // 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 libusbx 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
+ * - libusbx 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 libusbx
-libusb_get_pollfds()
+libusb_get_pollfds(ctx)
while (user has not requested application exit) {
- libusb_get_next_timeout();
- select(on libusb file descriptors plus any other event sources of interest,
- using a timeout no larger than the value libusb just suggested)
- if (select() indicated activity on libusb file descriptors)
- libusb_handle_events_timeout(0);
- if (time has elapsed to or beyond the libusb timeout)
- libusb_handle_events_timeout(0);
+ poll(on libusbx file descriptors plus any other event sources of interest,
+ using any timeout that you like)
+ if (poll() indicated activity on libusbx file descriptors)
+ libusb_handle_events_timeout(ctx, &zero_tv);
+ // handle events from other sources here
}
// clean up and exit
\endcode
*
- * The set of file descriptors that libusb uses as event sources may change
+ * 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 libusbx 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 libusbx'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 libusbx 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
+ *
+ * libusbx is a thread-safe library, but extra considerations must be applied
+ * to applications which interact with libusbx from multiple threads.
+ *
+ * The underlying issue that must be addressed is that all libusbx 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 libusbx'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 libusbx
+ * 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(libusbx file descriptors, 120*1000);
+ if (poll indicates activity)
+ libusb_handle_events_timeout(ctx, &zero_tv);
+ }
+ 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 libusbx'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 libusbx 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 its variants, and all the
+ * synchronous I/O functions - libusbx hides this headache from you.
+ *
+ * \section Using libusb_handle_events() from multiple threads
+ *
+ * Even when only using libusb_handle_events() and synchronous I/O functions,
+ * you can still have a race condition. You might be tempted to solve the
+ * above with libusb_handle_events() like so:
+ *
+\code
+ libusb_submit_transfer(transfer);
+
+ while (!completed) {
+ libusb_handle_events(ctx);
+ }
+ printf("completed!");
+\endcode
+ *
+ * This however has a race between the checking of completed and
+ * libusb_handle_events() acquiring the events lock, so another thread
+ * could have completed the transfer, resulting in this thread hanging
+ * until either a timeout or another event occurs. See also commit
+ * 6696512aade99bb15d6792af90ae329af270eba6 which fixes this in the
+ * synchronous API implementation of libusb.
+ *
+ * Fixing this race requires checking the variable completed only after
+ * taking the event lock, which defeats the concept of just calling
+ * libusb_handle_events() without worrying about locking. This is why
+ * libusb-1.0.9 introduces the new libusb_handle_events_timeout_completed()
+ * and libusb_handle_events_completed() functions, which handles doing the
+ * completion check for you after they have acquired the lock:
+ *
+\code
+ libusb_submit_transfer(transfer);
+
+ while (!completed) {
+ libusb_handle_events_completed(ctx, &completed);
+ }
+ printf("completed!");
+\endcode
+ *
+ * This nicely fixes the race in our example. Note that if all you want to
+ * do is submit a single transfer and wait for its completion, then using
+ * one of the synchronous I/O functions is much easier.
+ *
+ * \section eventlock The events lock
+ *
+ * The problem is when we consider the fact that libusbx 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
+ * libusbx's back. If you do take libusbx's file descriptors and pass them to
+ * poll()/select() yourself, you need to be aware of the associated issues.
+ *
+ * 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 libusbx 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(libusbx file descriptors, 120*1000);
+ if (poll indicates activity)
+ libusb_handle_events_timeout(ctx, &zero_tv);
+ }
+ 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, libusbx 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(libusbx 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 libusbx is still happy for your
+ * thread to be performing event handling. Sometimes, libusbx 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 libusbx'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 libusbx 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 libusbx'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.
+ *
+ * libusbx 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, libusbx 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(), libusbx writes some dummy data on this control pipe.
+ * This immediately interrupts the event handler. libusbx 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(), libusbx 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.
+ * -# libusbx 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 libusbx'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.
*/
-void usbi_io_init()
+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_recursive(&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)
{
- list_init(&flying_transfers);
- list_init(&pollfds);
- fd_added_cb = NULL;
- fd_removed_cb = NULL;
+ 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;
+ USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
if (!timeout)
return 0;
- r = clock_gettime(CLOCK_MONOTONIC, ¤t_time);
+ r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, ¤t_time);
if (r < 0) {
- usbi_err("failed to read monotonic clock, errno=%d", errno);
+ usbi_err(ITRANSFER_CTX(transfer),
+ "failed to read monotonic clock, errno=%d", errno);
return r;
}
return 0;
}
-static void add_to_flying_list(struct usbi_transfer *transfer)
+/* 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;
-
- pthread_mutex_lock(&flying_transfers_lock);
+ 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(&flying_transfers)) {
- list_add(&transfer->list, &flying_transfers);
+ if (list_empty(&ctx->flying_transfers)) {
+ list_add(&transfer->list, &ctx->flying_transfers);
goto out;
}
/* if we have infinite timeout, append to end of list */
if (!timerisset(timeout)) {
- list_add_tail(&transfer->list, &flying_transfers);
+ list_add_tail(&transfer->list, &ctx->flying_transfers);
+ /* first is irrelevant in this case */
goto out;
}
/* otherwise, find appropriate place in list */
- list_for_each_entry(cur, &flying_transfers, 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;
list_add_tail(&transfer->list, &cur->list);
goto out;
}
+ first = 0;
}
+ /* first is 0 at this stage (list not empty) */
/* otherwise we need to be inserted at the end */
- list_add_tail(&transfer->list, &flying_transfers);
+ list_add_tail(&transfer->list, &ctx->flying_transfers);
out:
- pthread_mutex_unlock(&flying_transfers_lock);
-}
-
-static int submit_transfer(struct usbi_transfer *itransfer)
-{
- int r = usbi_backend->submit_transfer(itransfer);
- if (r < 0)
- return r;
+#ifdef USBI_TIMERFD_AVAILABLE
+ if (first && usbi_using_timerfd(ctx) && timerisset(timeout)) {
+ /* 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},
+ { transfer->timeout.tv_sec, transfer->timeout.tv_usec * 1000 } };
+ usbi_dbg("arm timerfd for timeout in %dms (first in line)",
+ USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
+ r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
+ if (r < 0) {
+ usbi_warn(ctx, "failed to arm first timerfd (error %d)", r);
+ r = LIBUSB_ERROR_OTHER;
+ }
+ }
+#else
+ UNUSED(first);
+#endif
- add_to_flying_list(itransfer);
- return 0;
+ usbi_mutex_unlock(&ctx->flying_transfers_lock);
+ return r;
}
/** \ingroup asyncio
- * Allocate a libusb transfer with a specified number of isochronous packet
+ * Allocate a libusbx 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().
* 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::endpoint_type "endpoint_type" fields accordingly.
+ * \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 endpoint_type is set
- * appropriately.
+ * 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
*/
-API_EXPORTED struct libusb_transfer *libusb_alloc_transfer(int iso_packets)
+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);
- int alloc_size = sizeof(struct usbi_transfer)
+ 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);
+ struct usbi_transfer *itransfer = calloc(1, alloc_size);
if (!itransfer)
return NULL;
- memset(itransfer, 0, alloc_size);
itransfer->num_iso_packets = iso_packets;
- return __USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+ usbi_mutex_init(&itransfer->lock, NULL);
+ return USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
}
/** \ingroup asyncio
* 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
*/
-API_EXPORTED void libusb_free_transfer(struct libusb_transfer *transfer)
+void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer)
{
struct usbi_transfer *itransfer;
if (!transfer)
if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
free(transfer->buffer);
- itransfer = __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+ itransfer = LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+ usbi_mutex_destroy(&itransfer->lock);
free(itransfer);
}
+#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))
+ goto disarm;
+
+ /* 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;
+ }
+ }
+
+disarm:
+ return disarm_timerfd(ctx);
+}
+#else
+static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
+{
+ (void)ctx;
+ return 0;
+}
+#endif
+
/** \ingroup asyncio
* Submit a transfer. This function will fire off the USB transfer and then
* return immediately.
*
- * It is undefined behaviour to submit a transfer that has already been
- * submitted but has not yet completed.
- *
* \param transfer the transfer to submit
* \returns 0 on success
- * \returns negative on error
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted.
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED if the transfer flags are not supported
+ * by the operating system.
+ * \returns another LIBUSB_ERROR code on other failure
*/
-API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)
+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);
+ LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
int r;
+ int updated_fds;
+ usbi_mutex_lock(&itransfer->lock);
itransfer->transferred = 0;
+ itransfer->flags = 0;
r = calculate_timeout(itransfer);
- if (r < 0)
- return r;
+ if (r < 0) {
+ r = LIBUSB_ERROR_OTHER;
+ goto out;
+ }
- if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL) {
- struct libusb_control_setup *setup =
- (struct libusb_control_setup *) transfer->buffer;
-
- usbi_dbg("RQT=%02x RQ=%02x VAL=%04x IDX=%04x length=%d",
- setup->bmRequestType, setup->bRequest, setup->wValue, setup->wIndex,
- setup->wLength);
-
- setup->wValue = cpu_to_le16(setup->wValue);
- setup->wIndex = cpu_to_le16(setup->wIndex);
- setup->wLength = cpu_to_le16(setup->wLength);
+ r = add_to_flying_list(itransfer);
+ if (r)
+ goto out;
+ r = usbi_backend->submit_transfer(itransfer);
+ if (r) {
+ usbi_mutex_lock(&ctx->flying_transfers_lock);
+ list_del(&itransfer->list);
+ arm_timerfd_for_next_timeout(ctx);
+ usbi_mutex_unlock(&ctx->flying_transfers_lock);
}
- return submit_transfer(itransfer);
+out:
+ updated_fds = (itransfer->flags & USBI_TRANSFER_UPDATED_FDS);
+ usbi_mutex_unlock(&itransfer->lock);
+ if (updated_fds)
+ usbi_fd_notification(ctx);
+ return r;
}
/** \ingroup asyncio
* Asynchronously cancel a previously submitted transfer.
- * It is undefined behaviour to call this function on a transfer that is
- * already being cancelled or has already completed.
* 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
*
* \param transfer the transfer to cancel
* \returns 0 on success
- * \returns non-zero on error
+ * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is already complete or
+ * cancelled.
+ * \returns a LIBUSB_ERROR code on failure
*/
-API_EXPORTED int libusb_cancel_transfer(struct libusb_transfer *transfer)
+int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer)
{
struct usbi_transfer *itransfer =
- __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
- int r;
-
- usbi_dbg("");
- r = usbi_backend->cancel_transfer(itransfer);
- if (r < 0)
- usbi_err("cancel transfer failed error %d", r);
- return r;
-}
-
-/** \ingroup asyncio
- * Cancel a transfer and wait for cancellation completion without invoking
- * the transfer callback. This function will block.
- *
- * It is undefined behaviour to call this function on a transfer that is
- * already being cancelled or has already completed.
- *
- * \param transfer the transfer to cancel
- * \returns 0 on success
- * \returns non-zero on error
- */
-API_EXPORTED int libusb_cancel_transfer_sync(struct libusb_transfer *transfer)
-{
- struct usbi_transfer *itransfer =
- __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+ 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("cancel transfer failed error %d", r);
- return r;
- }
+ if (r != LIBUSB_ERROR_NOT_FOUND)
+ usbi_err(TRANSFER_CTX(transfer),
+ "cancel transfer failed error %d", r);
+ else
+ usbi_dbg("cancel transfer failed error %d", r);
- itransfer->flags |= USBI_TRANSFER_SYNC_CANCELLED;
- while (itransfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
- r = libusb_handle_events();
- if (r < 0)
- return r;
+ if (r == LIBUSB_ERROR_NO_DEVICE)
+ itransfer->flags |= USBI_TRANSFER_DEVICE_DISAPPEARED;
}
- return 0;
+ itransfer->flags |= USBI_TRANSFER_CANCELLING;
+
+ usbi_mutex_unlock(&itransfer->lock);
+ return r;
}
-void usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
+/* 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);
+ USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+ struct libusb_context *ctx = TRANSFER_CTX(transfer);
uint8_t flags;
+ int r = 0;
+
+ /* 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);
- if (status == LIBUSB_TRANSFER_SILENT_COMPLETION)
- return;
+ if (usbi_using_timerfd(ctx))
+ r = arm_timerfd_for_next_timeout(ctx);
+ usbi_mutex_unlock(&ctx->flying_transfers_lock);
+ if (usbi_using_timerfd(ctx) && (r < 0))
+ return r;
if (status == LIBUSB_TRANSFER_COMPLETED
&& transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
int rqlen = transfer->length;
- if (transfer->endpoint_type == LIBUSB_ENDPOINT_TYPE_CONTROL)
+ if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL)
rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
if (rqlen != itransfer->transferred) {
usbi_dbg("interpreting short transfer as error");
flags = transfer->flags;
transfer->status = status;
transfer->actual_length = itransfer->transferred;
+ usbi_dbg("transfer %p has callback %p", transfer, transfer->callback);
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;
}
-void usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
+/* 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 is being cancelled synchronously, raise cancellation
- * completion event by unsetting flag, and ensure that user callback does
- * not get called.
- */
- if (transfer->flags & USBI_TRANSFER_SYNC_CANCELLED) {
- transfer->flags &= ~USBI_TRANSFER_SYNC_CANCELLED;
- usbi_dbg("detected sync. cancel");
- usbi_handle_transfer_completion(transfer,
- LIBUSB_TRANSFER_SILENT_COMPLETION);
- return;
- }
-
/* 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");
- usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
- return;
+ return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
}
/* otherwise its a normal async cancel */
- usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
+ 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 libusbx 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 libusbx's file descriptors directly.
+ * If you stick to libusbx'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 libusbx 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 libusbx's file descriptors directly.
+ * If you stick to libusbx'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, libusbx 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 libusbx's file descriptors directly,
+ * <b>and</b> may potentially be handling events from 2 threads simultaenously.
+ * If you stick to libusbx'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);
+ USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
int r;
itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
r = libusb_cancel_transfer(transfer);
if (r < 0)
- usbi_warn("async cancel failed %d errno=%d", r, errno);
+ usbi_warn(TRANSFER_CTX(transfer),
+ "async cancel failed %d errno=%d", r, errno);
}
-static int handle_timeouts(void)
+static int handle_timeouts_locked(struct libusb_context *ctx)
{
+ int r;
struct timespec systime_ts;
struct timeval systime;
struct usbi_transfer *transfer;
- int r = 0;
- pthread_mutex_lock(&flying_transfers_lock);
- if (list_empty(&flying_transfers))
- goto out;
+ if (list_empty(&ctx->flying_transfers))
+ return 0;
/* get current time */
- r = clock_gettime(CLOCK_MONOTONIC, &systime_ts);
+ r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &systime_ts);
if (r < 0)
- goto out;
+ 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, &flying_transfers, list) {
+ 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))
- goto out;
+ return 0;
/* ignore timeouts we've already handled */
- if (transfer->flags & USBI_TRANSFER_TIMED_OUT)
+ if (transfer->flags & (USBI_TRANSFER_TIMED_OUT | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
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))
- goto out;
-
+ return 0;
+
/* otherwise, we've got an expired timeout to handle */
handle_timeout(transfer);
}
+ return 0;
+}
-out:
- pthread_mutex_unlock(&flying_transfers_lock);
+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;
}
-static int handle_events(struct timeval *tv)
+#ifdef USBI_TIMERFD_AVAILABLE
+static int handle_timerfd_trigger(struct libusb_context *ctx)
{
int r;
- int maxfd = 0;
- fd_set readfds, writefds;
- fd_set *_readfds = NULL;
- fd_set *_writefds = NULL;
- struct usbi_pollfd *ipollfd;
- int have_readfds = 0;
- int have_writefds = 0;
- struct timeval select_timeout;
- struct timeval timeout;
- r = libusb_get_next_timeout(&timeout);
- if (r) {
- /* timeout already expired? */
- if (!timerisset(&timeout))
- return handle_timeouts();
+ usbi_mutex_lock(&ctx->flying_transfers_lock);
- /* choose the smallest of next URB timeout or user specified timeout */
- if (timercmp(&timeout, tv, <))
- select_timeout = timeout;
- else
- select_timeout = *tv;
- } else {
- select_timeout = *tv;
+ /* 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;
+ POLL_NFDS_TYPE nfds = 0;
+ struct pollfd *fds = NULL;
+ 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 */
+ if (nfds != 0)
+ fds = malloc(sizeof(*fds) * nfds);
+ if (!fds) {
+ usbi_mutex_unlock(&ctx->pollfds_lock);
+ return LIBUSB_ERROR_NO_MEM;
}
- FD_ZERO(&readfds);
- FD_ZERO(&writefds);
- list_for_each_entry(ipollfd, &pollfds, list) {
+ list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) {
struct libusb_pollfd *pollfd = &ipollfd->pollfd;
int fd = pollfd->fd;
- if (pollfd->events & POLLIN) {
- have_readfds = 1;
- FD_SET(fd, &readfds);
- }
- if (pollfd->events & POLLOUT) {
- have_writefds = 1;
- FD_SET(fd, &writefds);
- }
- if (fd > maxfd)
- maxfd = 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);
- if (have_readfds)
- _readfds = &readfds;
- if (have_writefds)
- _writefds = &writefds;
+ /* round up to next millisecond */
+ if (tv->tv_usec % 1000)
+ timeout_ms++;
- usbi_dbg("select() with timeout in %d.%06ds", select_timeout.tv_sec,
- select_timeout.tv_usec);
- r = select(maxfd + 1, _readfds, _writefds, NULL, &select_timeout);
- usbi_dbg("select() returned %d with %d.%06ds remaining",
- r, select_timeout.tv_sec, select_timeout.tv_usec);
+ 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) {
- *tv = select_timeout;
- return handle_timeouts();
+ free(fds);
+ return handle_timeouts(ctx);
} else if (r == -1 && errno == EINTR) {
- return 0;
+ free(fds);
+ return LIBUSB_ERROR_INTERRUPTED;
} else if (r < 0) {
- usbi_err("select failed %d err=%d\n", r, errno);
- return r;
+ free(fds);
+ usbi_err(ctx, "poll failed %d err=%d\n", r, errno);
+ return LIBUSB_ERROR_IO;
}
- r = usbi_backend->handle_events(_readfds, _writefds);
- if (r < 0)
- return r;
+ /* 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;
- /* FIXME check return value? */
- return handle_timeouts();
+ /* 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
+ * libusbx 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
* timeout. If an event arrives or a signal is raised, this function will
* return early.
*
- * \param tv the maximum time to block waiting for events, or zero for
- * non-blocking mode
- * \returns 0 on success
- * \returns non-zero on error
+ * If the parameter completed is not NULL then <em>after obtaining the event
+ * handling lock</em> this function will return immediately if the integer
+ * pointed to is not 0. This allows for race free waiting for the completion
+ * of a specific transfer.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv the maximum time to block waiting for events, or an all zero
+ * timeval struct for non-blocking mode
+ * \param completed pointer to completion integer to check, or NULL
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \see \ref mtasync
+ */
+int API_EXPORTED libusb_handle_events_timeout_completed(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) {
+ 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 thread events that
+ * notify event completion. */
+ libusb_lock_event_waiters(ctx);
+
+ if (completed && *completed)
+ goto already_done;
+
+ 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");
+ r = libusb_wait_for_event(ctx, &poll_timeout);
+
+already_done:
+ libusb_unlock_event_waiters(ctx);
+
+ if (r < 0)
+ return r;
+ else if (r == 1)
+ return handle_timeouts(ctx);
+ else
+ return 0;
+}
+
+/** \ingroup poll
+ * Handle any pending events
+ *
+ * Like libusb_handle_events_timeout_completed(), but without the completed
+ * parameter, calling this function is equivalent to calling
+ * libusb_handle_events_timeout_completed() with a NULL completed parameter.
+ *
+ * This function is kept primarily for backwards compatibility.
+ * All new code should call libusb_handle_events_completed() or
+ * libusb_handle_events_timeout_completed() to avoid race conditions.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv the maximum time to block waiting for events, or an all zero
+ * timeval struct for non-blocking mode
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
*/
-API_EXPORTED int libusb_handle_events_timeout(struct timeval *tv)
+int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx,
+ struct timeval *tv)
{
- return handle_events(tv);
+ return libusb_handle_events_timeout_completed(ctx, tv, NULL);
}
/** \ingroup poll
- * Handle any pending events in blocking mode with a sensible timeout. This
- * timeout is currently hardcoded at 2 seconds but we may change this if we
- * decide other values are more sensible. For finer control over whether this
- * function is blocking or non-blocking, or the maximum timeout, use
- * libusb_handle_events_timeout() instead.
+ * 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_completed()
+ * instead.
+ *
+ * This function is kept primarily for backwards compatibility.
+ * All new code should call libusb_handle_events_completed() or
+ * libusb_handle_events_timeout_completed() to avoid race conditions.
+ *
+ * \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_completed(ctx, &tv, NULL);
+}
+
+/** \ingroup poll
+ * Handle any pending events in blocking mode.
*
- * \returns 0 on success
- * \returns non-zero on error
+ * Like libusb_handle_events(), with the addition of a completed parameter
+ * to allow for race free waiting for the completion of a specific transfer.
+ *
+ * See libusb_handle_events_timeout_completed() for details on the completed
+ * parameter.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param completed pointer to completion integer to check, or NULL
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \see \ref mtasync
*/
-API_EXPORTED int libusb_handle_events(void)
+int API_EXPORTED libusb_handle_events_completed(libusb_context *ctx,
+ int *completed)
{
struct timeval tv;
- tv.tv_sec = 2;
+ tv.tv_sec = 60;
tv.tv_usec = 0;
- return handle_events(&tv);
+ return libusb_handle_events_timeout_completed(ctx, &tv, completed);
}
/** \ingroup poll
- * Determine the next internal timeout that libusb needs to handle. You only
+ * 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 libusbx's
+ * file descriptors (as opposed to using libusb_handle_events() or similar).
+ * You detect events on libusbx'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 libusbx's file descriptors.
+ *
+ * This function is only useful for applications which retrieve and poll
+ * libusbx's file descriptors in their own main loop (\ref pollmain).
+ *
+ * Ordinarily, libusbx'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 libusbx 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 libusbx 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 libusbx file descriptors for event handling"
+ */
+int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx)
+{
+#if defined(USBI_TIMERFD_AVAILABLE)
+ USBI_GET_CONTEXT(ctx);
+ return usbi_using_timerfd(ctx);
+#else
+ (void)ctx;
+ return 0;
+#endif
+}
+
+/** \ingroup poll
+ * Determine the next internal timeout that libusbx 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
+ * on libusbx'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
+ * long to wait for select() or poll() to return results. libusbx 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.
+ * (perhaps in non-blocking mode) so that libusbx can handle the timeout.
*
- * This function may return 0 (success) and an all-zero timeval. If this is
- * the case, it indicates that libusb has a timeout that has already expired
+ * This function may return 1 (success) and an all-zero timeval. If this is
+ * the case, it indicates that libusbx 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 on success
- * \returns non-zero on error
+ * clock in which libusbx 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
*/
-API_EXPORTED int libusb_get_next_timeout(struct timeval *tv)
+int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx,
+ struct timeval *tv)
{
struct usbi_transfer *transfer;
struct timespec cur_ts;
int r;
int found = 0;
- pthread_mutex_lock(&flying_transfers_lock);
- if (list_empty(&flying_transfers)) {
- pthread_mutex_unlock(&flying_transfers_lock);
+ 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, &flying_transfers, list) {
- if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) {
- found = 1;
- break;
- }
+ list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+ if (transfer->flags & (USBI_TRANSFER_TIMED_OUT | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
+ continue;
+
+ /* no timeout for this transfer? */
+ if (!timerisset(&transfer->timeout))
+ continue;
+
+ found = 1;
+ break;
}
- pthread_mutex_unlock(&flying_transfers_lock);
+ usbi_mutex_unlock(&ctx->flying_transfers_lock);
if (!found) {
- usbi_dbg("all URBs have already been processed for timeouts");
+ usbi_dbg("no URB with timeout or all handled by OS; no timeout!");
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 = clock_gettime(CLOCK_MONOTONIC, &cur_ts);
+ r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &cur_ts);
if (r < 0) {
- usbi_err("failed to read monotonic clock, errno=%d", errno);
- return r;
+ usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno);
+ return 0;
}
TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
- if (timercmp(&cur_tv, next_timeout, >=)) {
+ if (!timercmp(&cur_tv, next_timeout, <)) {
usbi_dbg("first timeout already expired");
timerclear(tv);
} else {
/** \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.
+ * that libusbx 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)
*/
-API_EXPORTED void libusb_set_pollfd_notifiers(libusb_pollfd_added_cb added_cb,
- libusb_pollfd_removed_cb removed_cb)
+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)
{
- fd_added_cb = added_cb;
- fd_removed_cb = removed_cb;
+ USBI_GET_CONTEXT(ctx);
+ ctx->fd_added_cb = added_cb;
+ ctx->fd_removed_cb = removed_cb;
+ ctx->fd_cb_user_data = user_data;
}
-int usbi_add_pollfd(int fd, short events)
+/* 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 -ENOMEM;
+ return LIBUSB_ERROR_NO_MEM;
usbi_dbg("add fd %d events %d", fd, events);
ipollfd->pollfd.fd = fd;
ipollfd->pollfd.events = events;
- list_add(&ipollfd->list, &pollfds);
+ usbi_mutex_lock(&ctx->pollfds_lock);
+ list_add_tail(&ipollfd->list, &ctx->pollfds);
+ usbi_mutex_unlock(&ctx->pollfds_lock);
- if (fd_added_cb)
- fd_added_cb(fd, events);
+ if (ctx->fd_added_cb)
+ ctx->fd_added_cb(fd, events, ctx->fd_cb_user_data);
return 0;
}
-void usbi_remove_pollfd(int fd)
+/* 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);
- list_for_each_entry(ipollfd, &pollfds, list)
+ 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_err("couldn't find fd %d to remove", fd);
+ 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 (fd_removed_cb)
- fd_removed_cb(fd);
+ 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.
+ * as libusbx event sources.
*
* The returned list is NULL-terminated and should be freed with free() when
* done. The actual list contents must not be touched.
*
- * \returns a NULL-terminated list of libusb_pollfd structures, or NULL on
- * error
+ * 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
*/
-API_EXPORTED const struct libusb_pollfd **libusb_get_pollfds(void)
+DEFAULT_VISIBILITY
+const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
+ libusb_context *ctx)
{
- struct libusb_pollfd **ret;
+#ifndef OS_WINDOWS
+ struct libusb_pollfd **ret = NULL;
struct usbi_pollfd *ipollfd;
size_t i = 0;
size_t cnt = 0;
+ USBI_GET_CONTEXT(ctx);
- list_for_each_entry(ipollfd, &pollfds, list)
+ 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)
- return NULL;
+ goto out;
- list_for_each_entry(ipollfd, &pollfds, list)
+ 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
+ usbi_err(ctx, "external polling of libusbx's internal descriptors "\
+ "is not yet supported on Windows platforms");
+ 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);
+ }
+
+}
projects / platform / upstream / libusb.git / blobdiff