| Index: third_party/libusb/libusb/io.c
|
| diff --git a/third_party/libusb/libusb/io.c b/third_party/libusb/libusb/io.c
|
| new file mode 100644
|
| index 0000000000000000000000000000000000000000..51b641d3abd60bbaa6801434f2c85b779247d611
|
| --- /dev/null
|
| +++ b/third_party/libusb/libusb/io.c
|
| @@ -0,0 +1,2445 @@
|
| +/*
|
| + * I/O functions for libusb
|
| + * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
|
| + * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
|
| + *
|
| + * This library is free software; you can redistribute it and/or
|
| + * modify it under the terms of the GNU Lesser General Public
|
| + * License as published by the Free Software Foundation; either
|
| + * version 2.1 of the License, or (at your option) any later version.
|
| + *
|
| + * This library is distributed in the hope that it will be useful,
|
| + * but WITHOUT ANY WARRANTY; without even the implied warranty of
|
| + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
| + * Lesser General Public License for more details.
|
| + *
|
| + * You should have received a copy of the GNU Lesser General Public
|
| + * License along with this library; if not, write to the Free Software
|
| + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
| + */
|
| +
|
| +#include <config.h>
|
| +#include <errno.h>
|
| +#include <signal.h>
|
| +#include <stdint.h>
|
| +#include <stdlib.h>
|
| +#include <string.h>
|
| +#include <time.h>
|
| +
|
| +#ifdef HAVE_SYS_TIME_H
|
| +#include <sys/time.h>
|
| +#endif
|
| +
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| +#include <sys/timerfd.h>
|
| +#endif
|
| +
|
| +#include "libusbi.h"
|
| +
|
| +/**
|
| + * \page io Synchronous and asynchronous device I/O
|
| + *
|
| + * \section intro Introduction
|
| + *
|
| + * If you're using libusb in your application, you're probably wanting to
|
| + * perform I/O with devices - you want to perform USB data transfers.
|
| + *
|
| + * libusb offers two separate interfaces for device I/O. This page aims to
|
| + * introduce the two in order to help you decide which one is more suitable
|
| + * for your application. You can also choose to use both interfaces in your
|
| + * application by considering each transfer on a case-by-case basis.
|
| + *
|
| + * Once you have read through the following discussion, you should consult the
|
| + * detailed API documentation pages for the details:
|
| + * - \ref syncio
|
| + * - \ref asyncio
|
| + *
|
| + * \section theory Transfers at a logical level
|
| + *
|
| + * At a logical level, USB transfers typically happen in two parts. For
|
| + * example, when reading data from a endpoint:
|
| + * -# A request for data is sent to the device
|
| + * -# Some time later, the incoming data is received by the host
|
| + *
|
| + * or when writing data to an endpoint:
|
| + *
|
| + * -# The data is sent to the device
|
| + * -# Some time later, the host receives acknowledgement from the device that
|
| + * the data has been transferred.
|
| + *
|
| + * There may be an indefinite delay between the two steps. Consider a
|
| + * fictional USB input device with a button that the user can press. In order
|
| + * to determine when the button is pressed, you would likely submit a request
|
| + * to read data on a bulk or interrupt endpoint and wait for data to arrive.
|
| + * Data will arrive when the button is pressed by the user, which is
|
| + * potentially hours later.
|
| + *
|
| + * libusb offers both a synchronous and an asynchronous interface to performing
|
| + * USB transfers. The main difference is that the synchronous interface
|
| + * combines both steps indicated above into a single function call, whereas
|
| + * the asynchronous interface separates them.
|
| + *
|
| + * \section sync The synchronous interface
|
| + *
|
| + * The synchronous I/O interface allows you to perform a USB transfer with
|
| + * a single function call. When the function call returns, the transfer has
|
| + * completed and you can parse the results.
|
| + *
|
| + * If you have used the libusb-0.1 before, this I/O style will seem familar to
|
| + * you. libusb-0.1 only offered a synchronous interface.
|
| + *
|
| + * In our input device example, to read button presses you might write code
|
| + * in the following style:
|
| +\code
|
| +unsigned char data[4];
|
| +int actual_length;
|
| +int r = libusb_bulk_transfer(handle, 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
|
| +} else {
|
| + error();
|
| +}
|
| +\endcode
|
| + *
|
| + * The main advantage of this model is simplicity: you did everything with
|
| + * a single simple function call.
|
| + *
|
| + * However, this interface has its limitations. Your application will sleep
|
| + * inside libusb_bulk_transfer() until the transaction has completed. If it
|
| + * takes the user 3 hours to press the button, your application will be
|
| + * sleeping for that long. Execution will be tied up inside the library -
|
| + * the entire thread will be useless for that duration.
|
| + *
|
| + * Another issue is that by tieing up the thread with that single transaction
|
| + * there is no possibility of performing I/O with multiple endpoints and/or
|
| + * multiple devices simultaneously, unless you resort to creating one thread
|
| + * per transaction.
|
| + *
|
| + * Additionally, there is no opportunity to cancel the transfer after the
|
| + * request has been submitted.
|
| + *
|
| + * For details on how to use the synchronous API, see the
|
| + * \ref syncio "synchronous I/O API documentation" pages.
|
| + *
|
| + * \section async The asynchronous interface
|
| + *
|
| + * Asynchronous I/O is the most significant new feature in libusb-1.0.
|
| + * Although it is a more complex interface, it solves all the issues detailed
|
| + * above.
|
| + *
|
| + * Instead of providing which functions that block until the I/O has complete,
|
| + * libusb's asynchronous interface presents non-blocking functions which
|
| + * begin a transfer and then return immediately. Your application passes a
|
| + * callback function pointer to this non-blocking function, which libusb will
|
| + * call with the results of the transaction when it has completed.
|
| + *
|
| + * Transfers which have been submitted through the non-blocking functions
|
| + * can be cancelled with a separate function call.
|
| + *
|
| + * The non-blocking nature of this interface allows you to be simultaneously
|
| + * performing I/O to multiple endpoints on multiple devices, without having
|
| + * to use threads.
|
| + *
|
| + * This added flexibility does come with some complications though:
|
| + * - In the interest of being a lightweight library, libusb does not create
|
| + * threads and can only operate when your application is calling into it. Your
|
| + * application must call into libusb from it's main loop when events are ready
|
| + * to be handled, or you must use some other scheme to allow libusb to
|
| + * undertake whatever work needs to be done.
|
| + * - libusb also needs to be called into at certain fixed points in time in
|
| + * order to accurately handle transfer timeouts.
|
| + * - Memory handling becomes more complex. You cannot use stack memory unless
|
| + * the function with that stack is guaranteed not to return until the transfer
|
| + * callback has finished executing.
|
| + * - You generally lose some linearity from your code flow because submitting
|
| + * the transfer request is done in a separate function from where the transfer
|
| + * results are handled. This becomes particularly obvious when you want to
|
| + * submit a second transfer based on the results of an earlier transfer.
|
| + *
|
| + * Internally, libusb's synchronous interface is expressed in terms of function
|
| + * calls to the asynchronous interface.
|
| + *
|
| + * For details on how to use the asynchronous API, see the
|
| + * \ref asyncio "asynchronous I/O API" documentation pages.
|
| + */
|
| +
|
| +
|
| +/**
|
| + * \page packetoverflow Packets and overflows
|
| + *
|
| + * \section packets Packet abstraction
|
| + *
|
| + * The USB specifications describe how data is transmitted in packets, with
|
| + * constraints on packet size defined by endpoint descriptors. The host must
|
| + * not send data payloads larger than the endpoint's maximum packet size.
|
| + *
|
| + * libusb and the underlying OS abstract out the packet concept, allowing you
|
| + * to request transfers of any size. Internally, the request will be divided
|
| + * up into correctly-sized packets. You do not have to be concerned with
|
| + * packet sizes, but there is one exception when considering overflows.
|
| + *
|
| + * \section overflow Bulk/interrupt transfer overflows
|
| + *
|
| + * When requesting data on a bulk endpoint, libusb requires you to supply a
|
| + * buffer and the maximum number of bytes of data that libusb can put in that
|
| + * buffer. However, the size of the buffer is not communicated to the device -
|
| + * the device is just asked to send any amount of data.
|
| + *
|
| + * There is no problem if the device sends an amount of data that is less than
|
| + * or equal to the buffer size. libusb reports this condition to you through
|
| + * the \ref libusb_transfer::actual_length "libusb_transfer.actual_length"
|
| + * field.
|
| + *
|
| + * Problems may occur if the device attempts to send more data than can fit in
|
| + * the buffer. libusb reports LIBUSB_TRANSFER_OVERFLOW for this condition but
|
| + * other behaviour is largely undefined: actual_length may or may not be
|
| + * accurate, the chunk of data that can fit in the buffer (before overflow)
|
| + * may or may not have been transferred.
|
| + *
|
| + * Overflows are nasty, but can be avoided. Even though you were told to
|
| + * ignore packets above, think about the lower level details: each transfer is
|
| + * split into packets (typically small, with a maximum size of 512 bytes).
|
| + * Overflows can only happen if the final packet in an incoming data transfer
|
| + * is smaller than the actual packet that the device wants to transfer.
|
| + * Therefore, you will never see an overflow if your transfer buffer size is a
|
| + * multiple of the endpoint's packet size: the final packet will either
|
| + * fill up completely or will be only partially filled.
|
| + */
|
| +
|
| +/**
|
| + * @defgroup asyncio Asynchronous device I/O
|
| + *
|
| + * This page details libusb's asynchronous (non-blocking) API for USB device
|
| + * I/O. This interface is very powerful but is also quite complex - you will
|
| + * need to read this page carefully to understand the necessary considerations
|
| + * and issues surrounding use of this interface. Simplistic applications
|
| + * may wish to consider the \ref syncio "synchronous I/O API" instead.
|
| + *
|
| + * The asynchronous interface is built around the idea of separating transfer
|
| + * submission and handling of transfer completion (the synchronous model
|
| + * combines both of these into one). There may be a long delay between
|
| + * submission and completion, however the asynchronous submission function
|
| + * is non-blocking so will return control to your application during that
|
| + * potentially long delay.
|
| + *
|
| + * \section asyncabstraction Transfer abstraction
|
| + *
|
| + * For the asynchronous I/O, libusb implements the concept of a generic
|
| + * transfer entity for all types of I/O (control, bulk, interrupt,
|
| + * isochronous). The generic transfer object must be treated slightly
|
| + * differently depending on which type of I/O you are performing with it.
|
| + *
|
| + * This is represented by the public libusb_transfer structure type.
|
| + *
|
| + * \section asynctrf Asynchronous transfers
|
| + *
|
| + * We can view asynchronous I/O as a 5 step process:
|
| + * -# <b>Allocation</b>: allocate a libusb_transfer
|
| + * -# <b>Filling</b>: populate the libusb_transfer instance with information
|
| + * about the transfer you wish to perform
|
| + * -# <b>Submission</b>: ask libusb to submit the transfer
|
| + * -# <b>Completion handling</b>: examine transfer results in the
|
| + * libusb_transfer structure
|
| + * -# <b>Deallocation</b>: clean up resources
|
| + *
|
| + *
|
| + * \subsection asyncalloc Allocation
|
| + *
|
| + * This step involves allocating memory for a USB transfer. This is the
|
| + * generic transfer object mentioned above. At this stage, the transfer
|
| + * is "blank" with no details about what type of I/O it will be used for.
|
| + *
|
| + * Allocation is done with the libusb_alloc_transfer() function. You must use
|
| + * this function rather than allocating your own transfers.
|
| + *
|
| + * \subsection asyncfill Filling
|
| + *
|
| + * This step is where you take a previously allocated transfer and fill it
|
| + * with information to determine the message type and direction, data buffer,
|
| + * callback function, etc.
|
| + *
|
| + * You can either fill the required fields yourself or you can use the
|
| + * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
|
| + * and libusb_fill_interrupt_transfer().
|
| + *
|
| + * \subsection asyncsubmit Submission
|
| + *
|
| + * When you have allocated a transfer and filled it, you can submit it using
|
| + * libusb_submit_transfer(). This function returns immediately but can be
|
| + * regarded as firing off the I/O request in the background.
|
| + *
|
| + * \subsection asynccomplete Completion handling
|
| + *
|
| + * After a transfer has been submitted, one of four things can happen to it:
|
| + *
|
| + * - The transfer completes (i.e. some data was transferred)
|
| + * - The transfer has a timeout and the timeout expires before all data is
|
| + * transferred
|
| + * - The transfer fails due to an error
|
| + * - The transfer is cancelled
|
| + *
|
| + * Each of these will cause the user-specified transfer callback function to
|
| + * be invoked. It is up to the callback function to determine which of the
|
| + * above actually happened and to act accordingly.
|
| + *
|
| + * The user-specified callback is passed a pointer to the libusb_transfer
|
| + * structure which was used to setup and submit the transfer. At completion
|
| + * time, libusb has populated this structure with results of the transfer:
|
| + * success or failure reason, number of bytes of data transferred, etc. See
|
| + * the libusb_transfer structure documentation for more information.
|
| + *
|
| + * \subsection Deallocation
|
| + *
|
| + * When a transfer has completed (i.e. the callback function has been invoked),
|
| + * you are advised to free the transfer (unless you wish to resubmit it, see
|
| + * below). Transfers are deallocated with libusb_free_transfer().
|
| + *
|
| + * It is undefined behaviour to free a transfer which has not completed.
|
| + *
|
| + * \section asyncresubmit Resubmission
|
| + *
|
| + * You may be wondering why allocation, filling, and submission are all
|
| + * separated above where they could reasonably be combined into a single
|
| + * operation.
|
| + *
|
| + * The reason for separation is to allow you to resubmit transfers without
|
| + * having to allocate new ones every time. This is especially useful for
|
| + * common situations dealing with interrupt endpoints - you allocate one
|
| + * transfer, fill and submit it, and when it returns with results you just
|
| + * resubmit it for the next interrupt.
|
| + *
|
| + * \section asynccancel Cancellation
|
| + *
|
| + * Another advantage of using the asynchronous interface is that you have
|
| + * the ability to cancel transfers which have not yet completed. This is
|
| + * done by calling the libusb_cancel_transfer() function.
|
| + *
|
| + * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
|
| + * cancellation actually completes, the transfer's callback function will
|
| + * be invoked, and the callback function should check the transfer status to
|
| + * determine that it was cancelled.
|
| + *
|
| + * Freeing the transfer after it has been cancelled but before cancellation
|
| + * has completed will result in undefined behaviour.
|
| + *
|
| + * When a transfer is cancelled, some of the data may have been transferred.
|
| + * libusb will communicate this to you in the transfer callback. Do not assume
|
| + * that no data was transferred.
|
| + *
|
| + * \section bulk_overflows Overflows on device-to-host bulk/interrupt endpoints
|
| + *
|
| + * If your device does not have predictable transfer sizes (or it misbehaves),
|
| + * your application may submit a request for data on an IN endpoint which is
|
| + * smaller than the data that the device wishes to send. In some circumstances
|
| + * this will cause an overflow, which is a nasty condition to deal with. See
|
| + * the \ref packetoverflow page for discussion.
|
| + *
|
| + * \section asyncctrl Considerations for control transfers
|
| + *
|
| + * The <tt>libusb_transfer</tt> structure is generic and hence does not
|
| + * include specific fields for the control-specific setup packet structure.
|
| + *
|
| + * In order to perform a control transfer, you must place the 8-byte setup
|
| + * packet at the start of the data buffer. To simplify this, you could
|
| + * cast the buffer pointer to type struct libusb_control_setup, or you can
|
| + * use the helper function libusb_fill_control_setup().
|
| + *
|
| + * The wLength field placed in the setup packet must be the length you would
|
| + * expect to be sent in the setup packet: the length of the payload that
|
| + * follows (or the expected maximum number of bytes to receive). However,
|
| + * the length field of the libusb_transfer object must be the length of
|
| + * the data buffer - i.e. it should be wLength <em>plus</em> the size of
|
| + * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
|
| + *
|
| + * If you use the helper functions, this is simplified for you:
|
| + * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
|
| + * data you are sending/requesting.
|
| + * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
|
| + * request size as the wLength value (i.e. do not include the extra space you
|
| + * allocated for the control setup).
|
| + * -# If this is a host-to-device transfer, place the data to be transferred
|
| + * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
|
| + * -# Call libusb_fill_control_transfer() to associate the data buffer with
|
| + * the transfer (and to set the remaining details such as callback and timeout).
|
| + * - Note that there is no parameter to set the length field of the transfer.
|
| + * The length is automatically inferred from the wLength field of the setup
|
| + * packet.
|
| + * -# Submit the transfer.
|
| + *
|
| + * The multi-byte control setup fields (wValue, wIndex and wLength) must
|
| + * be given in little-endian byte order (the endianness of the USB bus).
|
| + * Endianness conversion is transparently handled by
|
| + * libusb_fill_control_setup() which is documented to accept host-endian
|
| + * values.
|
| + *
|
| + * Further considerations are needed when handling transfer completion in
|
| + * your callback function:
|
| + * - As you might expect, the setup packet will still be sitting at the start
|
| + * of the data buffer.
|
| + * - If this was a device-to-host transfer, the received data will be sitting
|
| + * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
|
| + * - The actual_length field of the transfer structure is relative to the
|
| + * wLength of the setup packet, rather than the size of the data buffer. So,
|
| + * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
|
| + * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
|
| + * transferred in entirity.
|
| + *
|
| + * To simplify parsing of setup packets and obtaining the data from the
|
| + * correct offset, you may wish to use the libusb_control_transfer_get_data()
|
| + * and libusb_control_transfer_get_setup() functions within your transfer
|
| + * callback.
|
| + *
|
| + * Even though control endpoints do not halt, a completed control transfer
|
| + * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control
|
| + * request was not supported.
|
| + *
|
| + * \section asyncintr Considerations for interrupt transfers
|
| + *
|
| + * All interrupt transfers are performed using the polling interval presented
|
| + * by the bInterval value of the endpoint descriptor.
|
| + *
|
| + * \section asynciso Considerations for isochronous transfers
|
| + *
|
| + * Isochronous transfers are more complicated than transfers to
|
| + * non-isochronous endpoints.
|
| + *
|
| + * To perform I/O to an isochronous endpoint, allocate the transfer by calling
|
| + * libusb_alloc_transfer() with an appropriate number of isochronous packets.
|
| + *
|
| + * During filling, set \ref libusb_transfer::type "type" to
|
| + * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
|
| + * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set
|
| + * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than
|
| + * or equal to the number of packets you requested during allocation.
|
| + * libusb_alloc_transfer() does not set either of these fields for you, given
|
| + * that you might not even use the transfer on an isochronous endpoint.
|
| + *
|
| + * Next, populate the length field for the first num_iso_packets entries in
|
| + * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section
|
| + * 5.6.3 of the USB2 specifications describe how the maximum isochronous
|
| + * packet length is determined by the wMaxPacketSize field in the endpoint
|
| + * descriptor.
|
| + * Two functions can help you here:
|
| + *
|
| + * - libusb_get_max_iso_packet_size() is an easy way to determine the max
|
| + * packet size for an isochronous endpoint. Note that the maximum packet
|
| + * size is actually the maximum number of bytes that can be transmitted in
|
| + * a single microframe, therefore this function multiplies the maximum number
|
| + * of bytes per transaction by the number of transaction opportunities per
|
| + * microframe.
|
| + * - libusb_set_iso_packet_lengths() assigns the same length to all packets
|
| + * within a transfer, which is usually what you want.
|
| + *
|
| + * For outgoing transfers, you'll obviously fill the buffer and populate the
|
| + * packet descriptors in hope that all the data gets transferred. For incoming
|
| + * transfers, you must ensure the buffer has sufficient capacity for
|
| + * the situation where all packets transfer the full amount of requested data.
|
| + *
|
| + * Completion handling requires some extra consideration. The
|
| + * \ref libusb_transfer::actual_length "actual_length" field of the transfer
|
| + * is meaningless and should not be examined; instead you must refer to the
|
| + * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of
|
| + * each individual packet.
|
| + *
|
| + * The \ref libusb_transfer::status "status" field of the transfer is also a
|
| + * little misleading:
|
| + * - If the packets were submitted and the isochronous data microframes
|
| + * completed normally, status will have value
|
| + * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED
|
| + * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred
|
| + * delays are not counted as transfer errors; the transfer.status field may
|
| + * indicate COMPLETED even if some or all of the packets failed. Refer to
|
| + * the \ref libusb_iso_packet_descriptor::status "status" field of each
|
| + * individual packet to determine packet failures.
|
| + * - The status field will have value
|
| + * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR
|
| + * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered.
|
| + * - Other transfer status codes occur with normal behaviour.
|
| + *
|
| + * The data for each packet will be found at an offset into the buffer that
|
| + * can be calculated as if each prior packet completed in full. The
|
| + * libusb_get_iso_packet_buffer() and libusb_get_iso_packet_buffer_simple()
|
| + * functions may help you here.
|
| + *
|
| + * \section asyncmem Memory caveats
|
| + *
|
| + * In most circumstances, it is not safe to use stack memory for transfer
|
| + * buffers. This is because the function that fired off the asynchronous
|
| + * transfer may return before libusb has finished using the buffer, and when
|
| + * the function returns it's stack gets destroyed. This is true for both
|
| + * host-to-device and device-to-host transfers.
|
| + *
|
| + * The only case in which it is safe to use stack memory is where you can
|
| + * guarantee that the function owning the stack space for the buffer does not
|
| + * return until after the transfer's callback function has completed. In every
|
| + * other case, you need to use heap memory instead.
|
| + *
|
| + * \section asyncflags Fine control
|
| + *
|
| + * Through using this asynchronous interface, you may find yourself repeating
|
| + * a few simple operations many times. You can apply a bitwise OR of certain
|
| + * flags to a transfer to simplify certain things:
|
| + * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
|
| + * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
|
| + * less than the requested amount of data being marked with status
|
| + * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
|
| + * (they would normally be regarded as COMPLETED)
|
| + * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
|
| + * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
|
| + * buffer when freeing the transfer.
|
| + * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
|
| + * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
|
| + * transfer after the transfer callback returns.
|
| + *
|
| + * \section asyncevent Event handling
|
| + *
|
| + * In accordance of the aim of being a lightweight library, libusb does not
|
| + * create threads internally. This means that libusb code does not execute
|
| + * at any time other than when your application is calling a libusb function.
|
| + * However, an asynchronous model requires that libusb perform work at various
|
| + * points in time - namely processing the results of previously-submitted
|
| + * transfers and invoking the user-supplied callback function.
|
| + *
|
| + * This gives rise to the libusb_handle_events() function which your
|
| + * application must call into when libusb has work do to. This gives libusb
|
| + * the opportunity to reap pending transfers, invoke callbacks, etc.
|
| + *
|
| + * The first issue to discuss here is how your application can figure out
|
| + * when libusb has work to do. In fact, there are two naive options which
|
| + * do not actually require your application to know this:
|
| + * -# Periodically call libusb_handle_events() in non-blocking mode at fixed
|
| + * short intervals from your main loop
|
| + * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated
|
| + * thread.
|
| + *
|
| + * The first option is plainly not very nice, and will cause unnecessary
|
| + * CPU wakeups leading to increased power usage and decreased battery life.
|
| + * The second option is not very nice either, but may be the nicest option
|
| + * available to you if the "proper" approach can not be applied to your
|
| + * application (read on...).
|
| + *
|
| + * The recommended option is to integrate libusb with your application main
|
| + * event loop. libusb exposes a set of file descriptors which allow you to do
|
| + * this. Your main loop is probably already calling poll() or select() or a
|
| + * variant on a set of file descriptors for other event sources (e.g. keyboard
|
| + * button presses, mouse movements, network sockets, etc). You then add
|
| + * libusb's file descriptors to your poll()/select() calls, and when activity
|
| + * is detected on such descriptors you know it is time to call
|
| + * libusb_handle_events().
|
| + *
|
| + * There is one final event handling complication. libusb supports
|
| + * asynchronous transfers which time out after a specified time period, and
|
| + * this requires that libusb is called into at or after the timeout so that
|
| + * the timeout can be handled. So, in addition to considering libusb's file
|
| + * descriptors in your main event loop, you must also consider that libusb
|
| + * sometimes needs to be called into at fixed points in time even when there
|
| + * is no file descriptor activity.
|
| + *
|
| + * For the details on retrieving the set of file descriptors and determining
|
| + * the next timeout, see the \ref poll "polling and timing" API documentation.
|
| + */
|
| +
|
| +/**
|
| + * @defgroup poll Polling and timing
|
| + *
|
| + * This page documents libusb's functions for polling events and timing.
|
| + * These functions are only necessary for users of the
|
| + * \ref asyncio "asynchronous API". If you are only using the simpler
|
| + * \ref syncio "synchronous API" then you do not need to ever call these
|
| + * functions.
|
| + *
|
| + * The justification for the functionality described here has already been
|
| + * discussed in the \ref asyncevent "event handling" section of the
|
| + * asynchronous API documentation. In summary, libusb does not create internal
|
| + * threads for event processing and hence relies on your application calling
|
| + * into libusb at certain points in time so that pending events can be handled.
|
| + * In order to know precisely when libusb needs to be called into, libusb
|
| + * offers you a set of pollable file descriptors and information about when
|
| + * the next timeout expires.
|
| + *
|
| + * If you are using the asynchronous I/O API, you must take one of the two
|
| + * following options, otherwise your I/O will not complete.
|
| + *
|
| + * \section pollsimple The simple option
|
| + *
|
| + * If your application revolves solely around libusb and does not need to
|
| + * handle other event sources, you can have a program structure as follows:
|
| +\code
|
| +// initialize libusb
|
| +// find and open device
|
| +// maybe fire off some initial async I/O
|
| +
|
| +while (user_has_not_requested_exit)
|
| + libusb_handle_events(ctx);
|
| +
|
| +// clean up and exit
|
| +\endcode
|
| + *
|
| + * With such a simple main loop, you do not have to worry about managing
|
| + * sets of file descriptors or handling timeouts. libusb_handle_events() will
|
| + * handle those details internally.
|
| + *
|
| + * \section pollmain The more advanced option
|
| + *
|
| + * \note This functionality is currently only available on Unix-like platforms.
|
| + * On Windows, libusb_get_pollfds() simply returns NULL. Exposing event sources
|
| + * on Windows will require some further thought and design.
|
| + *
|
| + * In more advanced applications, you will already have a main loop which
|
| + * is monitoring other event sources: network sockets, X11 events, mouse
|
| + * movements, etc. Through exposing a set of file descriptors, libusb is
|
| + * designed to cleanly integrate into such main loops.
|
| + *
|
| + * In addition to polling file descriptors for the other event sources, you
|
| + * take a set of file descriptors from libusb and monitor those too. When you
|
| + * detect activity on libusb's file descriptors, you call
|
| + * libusb_handle_events_timeout() in non-blocking mode.
|
| + *
|
| + * What's more, libusb may also need to handle events at specific moments in
|
| + * time. No file descriptor activity is generated at these times, so your
|
| + * own application needs to be continually aware of when the next one of these
|
| + * moments occurs (through calling libusb_get_next_timeout()), and then it
|
| + * needs to call libusb_handle_events_timeout() in non-blocking mode when
|
| + * these moments occur. This means that you need to adjust your
|
| + * poll()/select() timeout accordingly.
|
| + *
|
| + * libusb provides you with a set of file descriptors to poll and expects you
|
| + * to poll all of them, treating them as a single entity. The meaning of each
|
| + * file descriptor in the set is an internal implementation detail,
|
| + * platform-dependent and may vary from release to release. Don't try and
|
| + * interpret the meaning of the file descriptors, just do as libusb indicates,
|
| + * polling all of them at once.
|
| + *
|
| + * In pseudo-code, you want something that looks like:
|
| +\code
|
| +// initialise libusb
|
| +
|
| +libusb_get_pollfds(ctx)
|
| +while (user has not requested application exit) {
|
| + libusb_get_next_timeout(ctx);
|
| + poll(on libusb file descriptors plus any other event sources of interest,
|
| + using a timeout no larger than the value libusb just suggested)
|
| + if (poll() indicated activity on libusb file descriptors)
|
| + libusb_handle_events_timeout(ctx, &zero_tv);
|
| + if (time has elapsed to or beyond the libusb 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 libusb at
|
| + * specific moments is a bit of a headache. For maximum compatibility, you do
|
| + * need to write your main loop as above, but you may decide that you can
|
| + * restrict the supported platforms of your application and get away with
|
| + * a more simplistic scheme.
|
| + *
|
| + * These time-based event complications are \b not required on the following
|
| + * platforms:
|
| + * - Darwin
|
| + * - Linux, provided that the following version requirements are satisfied:
|
| + * - Linux v2.6.27 or newer, compiled with timerfd support
|
| + * - glibc v2.9 or newer
|
| + * - libusb v1.0.5 or newer
|
| + *
|
| + * Under these configurations, libusb_get_next_timeout() will \em always return
|
| + * 0, so your main loop can be simplified to:
|
| +\code
|
| +// initialise libusb
|
| +
|
| +libusb_get_pollfds(ctx)
|
| +while (user has not requested application exit) {
|
| + poll(on libusb file descriptors plus any other event sources of interest,
|
| + using any timeout that you like)
|
| + if (poll() indicated activity on libusb file descriptors)
|
| + libusb_handle_events_timeout(ctx, &zero_tv);
|
| + // handle events from other sources here
|
| +}
|
| +
|
| +// clean up and exit
|
| +\endcode
|
| + *
|
| + * Do remember that if you simplify your main loop to the above, you will
|
| + * lose compatibility with some platforms (including legacy Linux platforms,
|
| + * and <em>any future platforms supported by libusb which may have time-based
|
| + * event requirements</em>). The resultant problems will likely appear as
|
| + * strange bugs in your application.
|
| + *
|
| + * You can use the libusb_pollfds_handle_timeouts() function to do a runtime
|
| + * check to see if it is safe to ignore the time-based event complications.
|
| + * If your application has taken the shortcut of ignoring libusb's next timeout
|
| + * in your main loop, then you are advised to check the return value of
|
| + * libusb_pollfds_handle_timeouts() during application startup, and to abort
|
| + * if the platform does suffer from these timing complications.
|
| + *
|
| + * \subsection fdsetchange Changes in the file descriptor set
|
| + *
|
| + * The set of file descriptors that libusb uses as event sources may change
|
| + * during the life of your application. Rather than having to repeatedly
|
| + * call libusb_get_pollfds(), you can set up notification functions for when
|
| + * the file descriptor set changes using libusb_set_pollfd_notifiers().
|
| + *
|
| + * \subsection mtissues Multi-threaded considerations
|
| + *
|
| + * Unfortunately, the situation is complicated further when multiple threads
|
| + * come into play. If two threads are monitoring the same file descriptors,
|
| + * the fact that only one thread will be woken up when an event occurs causes
|
| + * some headaches.
|
| + *
|
| + * The events lock, event waiters lock, and libusb_handle_events_locked()
|
| + * entities are added to solve these problems. You do not need to be concerned
|
| + * with these entities otherwise.
|
| + *
|
| + * See the extra documentation: \ref mtasync
|
| + */
|
| +
|
| +/** \page mtasync Multi-threaded applications and asynchronous I/O
|
| + *
|
| + * libusb is a thread-safe library, but extra considerations must be applied
|
| + * to applications which interact with libusb from multiple threads.
|
| + *
|
| + * The underlying issue that must be addressed is that all libusb I/O
|
| + * revolves around monitoring file descriptors through the poll()/select()
|
| + * system calls. This is directly exposed at the
|
| + * \ref asyncio "asynchronous interface" but it is important to note that the
|
| + * \ref syncio "synchronous interface" is implemented on top of the
|
| + * asynchonrous interface, therefore the same considerations apply.
|
| + *
|
| + * The issue is that if two or more threads are concurrently calling poll()
|
| + * or select() on libusb's file descriptors then only one of those threads
|
| + * will be woken up when an event arrives. The others will be completely
|
| + * oblivious that anything has happened.
|
| + *
|
| + * Consider the following pseudo-code, which submits an asynchronous transfer
|
| + * then waits for its completion. This style is one way you could implement a
|
| + * synchronous interface on top of the asynchronous interface (and libusb
|
| + * does something similar, albeit more advanced due to the complications
|
| + * explained on this page).
|
| + *
|
| +\code
|
| +void cb(struct libusb_transfer *transfer)
|
| +{
|
| + int *completed = transfer->user_data;
|
| + *completed = 1;
|
| +}
|
| +
|
| +void myfunc() {
|
| + struct libusb_transfer *transfer;
|
| + unsigned char buffer[LIBUSB_CONTROL_SETUP_SIZE];
|
| + int completed = 0;
|
| +
|
| + transfer = libusb_alloc_transfer(0);
|
| + libusb_fill_control_setup(buffer,
|
| + LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT, 0x04, 0x01, 0, 0);
|
| + libusb_fill_control_transfer(transfer, dev, buffer, cb, &completed, 1000);
|
| + libusb_submit_transfer(transfer);
|
| +
|
| + while (!completed) {
|
| + poll(libusb file descriptors, 120*1000);
|
| + if (poll indicates activity)
|
| + libusb_handle_events_timeout(ctx, &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 libusb's file descriptors, there
|
| + * is no problem: there is no danger that another thread will swallow up the
|
| + * event that we are interested in. On the other hand, if there is another
|
| + * thread polling the same descriptors, there is a chance that it will receive
|
| + * the event that we were interested in. In this situation, <tt>myfunc()</tt>
|
| + * will only realise that the transfer has completed on the next iteration of
|
| + * the loop, <em>up to 120 seconds later.</em> Clearly a two-minute delay is
|
| + * undesirable, and don't even think about using short timeouts to circumvent
|
| + * this issue!
|
| + *
|
| + * The solution here is to ensure that no two threads are ever polling the
|
| + * file descriptors at the same time. A naive implementation of this would
|
| + * impact the capabilities of the library, so libusb offers the scheme
|
| + * documented below to ensure no loss of functionality.
|
| + *
|
| + * Before we go any further, it is worth mentioning that all libusb-wrapped
|
| + * event handling procedures fully adhere to the scheme documented below.
|
| + * This includes libusb_handle_events() and its variants, and all the
|
| + * synchronous I/O functions - libusb 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 libusb exposes file
|
| + * descriptors to allow for you to integrate asynchronous USB I/O into
|
| + * existing main loops, effectively allowing you to do some work behind
|
| + * libusb's back. If you do take libusb's file descriptors and pass them to
|
| + * poll()/select() yourself, you need to be aware of the associated issues.
|
| + *
|
| + * The first concept to be introduced is the events lock. The events lock
|
| + * is used to serialize threads that want to handle events, such that only
|
| + * one thread is handling events at any one time.
|
| + *
|
| + * You must take the events lock before polling libusb file descriptors,
|
| + * using libusb_lock_events(). You must release the lock as soon as you have
|
| + * aborted your poll()/select() loop, using libusb_unlock_events().
|
| + *
|
| + * \section threadwait Letting other threads do the work for you
|
| + *
|
| + * Although the events lock is a critical part of the solution, it is not
|
| + * enough on it's own. You might wonder if the following is sufficient...
|
| +\code
|
| + libusb_lock_events(ctx);
|
| + while (!completed) {
|
| + poll(libusb file descriptors, 120*1000);
|
| + if (poll indicates activity)
|
| + libusb_handle_events_timeout(ctx, &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, libusb offers you a mechanism to determine when another
|
| + * thread is handling events. It also offers a mechanism to block your thread
|
| + * until the event handling thread has completed an event (and this mechanism
|
| + * does not involve polling of file descriptors).
|
| + *
|
| + * After determining that another thread is currently handling events, you
|
| + * obtain the <em>event waiters</em> lock using libusb_lock_event_waiters().
|
| + * You then re-check that some other thread is still handling events, and if
|
| + * so, you call libusb_wait_for_event().
|
| + *
|
| + * libusb_wait_for_event() puts your application to sleep until an event
|
| + * occurs, or until a thread releases the events lock. When either of these
|
| + * things happen, your thread is woken up, and should re-check the condition
|
| + * it was waiting on. It should also re-check that another thread is handling
|
| + * events, and if not, it should start handling events itself.
|
| + *
|
| + * This looks like the following, as pseudo-code:
|
| +\code
|
| +retry:
|
| +if (libusb_try_lock_events(ctx) == 0) {
|
| + // we obtained the event lock: do our own event handling
|
| + while (!completed) {
|
| + if (!libusb_event_handling_ok(ctx)) {
|
| + libusb_unlock_events(ctx);
|
| + goto retry;
|
| + }
|
| + poll(libusb file descriptors, 120*1000);
|
| + if (poll indicates activity)
|
| + libusb_handle_events_locked(ctx, 0);
|
| + }
|
| + libusb_unlock_events(ctx);
|
| +} else {
|
| + // another thread is doing event handling. wait for it to signal us that
|
| + // an event has completed
|
| + libusb_lock_event_waiters(ctx);
|
| +
|
| + while (!completed) {
|
| + // now that we have the event waiters lock, double check that another
|
| + // thread is still handling events for us. (it may have ceased handling
|
| + // events in the time it took us to reach this point)
|
| + if (!libusb_event_handler_active(ctx)) {
|
| + // whoever was handling events is no longer doing so, try again
|
| + libusb_unlock_event_waiters(ctx);
|
| + goto retry;
|
| + }
|
| +
|
| + libusb_wait_for_event(ctx, NULL);
|
| + }
|
| + libusb_unlock_event_waiters(ctx);
|
| +}
|
| +printf("completed!\n");
|
| +\endcode
|
| + *
|
| + * A naive look at the above code may suggest that this can only support
|
| + * one event waiter (hence a total of 2 competing threads, the other doing
|
| + * event handling), because the event waiter seems to have taken the event
|
| + * waiters lock while waiting for an event. However, the system does support
|
| + * multiple event waiters, because libusb_wait_for_event() actually drops
|
| + * the lock while waiting, and reaquires it before continuing.
|
| + *
|
| + * We have now implemented code which can dynamically handle situations where
|
| + * nobody is handling events (so we should do it ourselves), and it can also
|
| + * handle situations where another thread is doing event handling (so we can
|
| + * piggyback onto them). It is also equipped to handle a combination of
|
| + * the two, for example, another thread is doing event handling, but for
|
| + * whatever reason it stops doing so before our condition is met, so we take
|
| + * over the event handling.
|
| + *
|
| + * Four functions were introduced in the above pseudo-code. Their importance
|
| + * should be apparent from the code shown above.
|
| + * -# libusb_try_lock_events() is a non-blocking function which attempts
|
| + * to acquire the events lock but returns a failure code if it is contended.
|
| + * -# libusb_event_handling_ok() checks that libusb is still happy for your
|
| + * thread to be performing event handling. Sometimes, libusb needs to
|
| + * interrupt the event handler, and this is how you can check if you have
|
| + * been interrupted. If this function returns 0, the correct behaviour is
|
| + * for you to give up the event handling lock, and then to repeat the cycle.
|
| + * The following libusb_try_lock_events() will fail, so you will become an
|
| + * events waiter. For more information on this, read \ref fullstory below.
|
| + * -# libusb_handle_events_locked() is a variant of
|
| + * libusb_handle_events_timeout() that you can call while holding the
|
| + * events lock. libusb_handle_events_timeout() itself implements similar
|
| + * logic to the above, so be sure not to call it when you are
|
| + * "working behind libusb's back", as is the case here.
|
| + * -# libusb_event_handler_active() determines if someone is currently
|
| + * holding the events lock
|
| + *
|
| + * You might be wondering why there is no function to wake up all threads
|
| + * blocked on libusb_wait_for_event(). This is because libusb can do this
|
| + * internally: it will wake up all such threads when someone calls
|
| + * libusb_unlock_events() or when a transfer completes (at the point after its
|
| + * callback has returned).
|
| + *
|
| + * \subsection fullstory The full story
|
| + *
|
| + * The above explanation should be enough to get you going, but if you're
|
| + * really thinking through the issues then you may be left with some more
|
| + * questions regarding libusb's internals. If you're curious, read on, and if
|
| + * not, skip to the next section to avoid confusing yourself!
|
| + *
|
| + * The immediate question that may spring to mind is: what if one thread
|
| + * modifies the set of file descriptors that need to be polled while another
|
| + * thread is doing event handling?
|
| + *
|
| + * There are 2 situations in which this may happen.
|
| + * -# libusb_open() will add another file descriptor to the poll set,
|
| + * therefore it is desirable to interrupt the event handler so that it
|
| + * restarts, picking up the new descriptor.
|
| + * -# libusb_close() will remove a file descriptor from the poll set. There
|
| + * are all kinds of race conditions that could arise here, so it is
|
| + * important that nobody is doing event handling at this time.
|
| + *
|
| + * libusb handles these issues internally, so application developers do not
|
| + * have to stop their event handlers while opening/closing devices. Here's how
|
| + * it works, focusing on the libusb_close() situation first:
|
| + *
|
| + * -# During initialization, libusb opens an internal pipe, and it adds the read
|
| + * end of this pipe to the set of file descriptors to be polled.
|
| + * -# During libusb_close(), libusb writes some dummy data on this control pipe.
|
| + * This immediately interrupts the event handler. libusb also records
|
| + * internally that it is trying to interrupt event handlers for this
|
| + * high-priority event.
|
| + * -# At this point, some of the functions described above start behaving
|
| + * differently:
|
| + * - libusb_event_handling_ok() starts returning 1, indicating that it is NOT
|
| + * OK for event handling to continue.
|
| + * - libusb_try_lock_events() starts returning 1, indicating that another
|
| + * thread holds the event handling lock, even if the lock is uncontended.
|
| + * - libusb_event_handler_active() starts returning 1, indicating that
|
| + * another thread is doing event handling, even if that is not true.
|
| + * -# The above changes in behaviour result in the event handler stopping and
|
| + * giving up the events lock very quickly, giving the high-priority
|
| + * libusb_close() operation a "free ride" to acquire the events lock. All
|
| + * threads that are competing to do event handling become event waiters.
|
| + * -# With the events lock held inside libusb_close(), libusb can safely remove
|
| + * a file descriptor from the poll set, in the safety of knowledge that
|
| + * nobody is polling those descriptors or trying to access the poll set.
|
| + * -# After obtaining the events lock, the close operation completes very
|
| + * quickly (usually a matter of milliseconds) and then immediately releases
|
| + * the events lock.
|
| + * -# At the same time, the behaviour of libusb_event_handling_ok() and friends
|
| + * reverts to the original, documented behaviour.
|
| + * -# The release of the events lock causes the threads that are waiting for
|
| + * events to be woken up and to start competing to become event handlers
|
| + * again. One of them will succeed; it will then re-obtain the list of poll
|
| + * descriptors, and USB I/O will then continue as normal.
|
| + *
|
| + * libusb_open() is similar, and is actually a more simplistic case. Upon a
|
| + * call to libusb_open():
|
| + *
|
| + * -# The device is opened and a file descriptor is added to the poll set.
|
| + * -# libusb sends some dummy data on the control pipe, and records that it
|
| + * is trying to modify the poll descriptor set.
|
| + * -# The event handler is interrupted, and the same behaviour change as for
|
| + * libusb_close() takes effect, causing all event handling threads to become
|
| + * event waiters.
|
| + * -# The libusb_open() implementation takes its free ride to the events lock.
|
| + * -# Happy that it has successfully paused the events handler, libusb_open()
|
| + * releases the events lock.
|
| + * -# The event waiter threads are all woken up and compete to become event
|
| + * handlers again. The one that succeeds will obtain the list of poll
|
| + * descriptors again, which will include the addition of the new device.
|
| + *
|
| + * \subsection concl Closing remarks
|
| + *
|
| + * The above may seem a little complicated, but hopefully I have made it clear
|
| + * why such complications are necessary. Also, do not forget that this only
|
| + * applies to applications that take libusb's file descriptors and integrate
|
| + * them into their own polling loops.
|
| + *
|
| + * You may decide that it is OK for your multi-threaded application to ignore
|
| + * some of the rules and locks detailed above, because you don't think that
|
| + * two threads can ever be polling the descriptors at the same time. If that
|
| + * is the case, then that's good news for you because you don't have to worry.
|
| + * But be careful here; remember that the synchronous I/O functions do event
|
| + * handling internally. If you have one thread doing event handling in a loop
|
| + * (without implementing the rules and locking semantics documented above)
|
| + * and another trying to send a synchronous USB transfer, you will end up with
|
| + * two threads monitoring the same descriptors, and the above-described
|
| + * undesirable behaviour occuring. The solution is for your polling thread to
|
| + * play by the rules; the synchronous I/O functions do so, and this will result
|
| + * in them getting along in perfect harmony.
|
| + *
|
| + * If you do have a dedicated thread doing event handling, it is perfectly
|
| + * legal for it to take the event handling lock for long periods of time. Any
|
| + * synchronous I/O functions you call from other threads will transparently
|
| + * fall back to the "event waiters" mechanism detailed above. The only
|
| + * consideration that your event handling thread must apply is the one related
|
| + * to libusb_event_handling_ok(): you must call this before every poll(), and
|
| + * give up the events lock if instructed.
|
| + */
|
| +
|
| +int usbi_io_init(struct libusb_context *ctx)
|
| +{
|
| + int r;
|
| +
|
| + usbi_mutex_init(&ctx->flying_transfers_lock, NULL);
|
| + usbi_mutex_init(&ctx->pollfds_lock, NULL);
|
| + usbi_mutex_init(&ctx->pollfd_modify_lock, NULL);
|
| + usbi_mutex_init_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)
|
| +{
|
| + usbi_remove_pollfd(ctx, ctx->ctrl_pipe[0]);
|
| + usbi_close(ctx->ctrl_pipe[0]);
|
| + usbi_close(ctx->ctrl_pipe[1]);
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| + if (usbi_using_timerfd(ctx)) {
|
| + usbi_remove_pollfd(ctx, ctx->timerfd);
|
| + close(ctx->timerfd);
|
| + }
|
| +#endif
|
| + usbi_mutex_destroy(&ctx->flying_transfers_lock);
|
| + usbi_mutex_destroy(&ctx->pollfds_lock);
|
| + usbi_mutex_destroy(&ctx->pollfd_modify_lock);
|
| + usbi_mutex_destroy(&ctx->events_lock);
|
| + usbi_mutex_destroy(&ctx->event_waiters_lock);
|
| + usbi_cond_destroy(&ctx->event_waiters_cond);
|
| +}
|
| +
|
| +static int calculate_timeout(struct usbi_transfer *transfer)
|
| +{
|
| + int r;
|
| + struct timespec current_time;
|
| + unsigned int timeout =
|
| + USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
|
| +
|
| + if (!timeout)
|
| + return 0;
|
| +
|
| + r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, ¤t_time);
|
| + if (r < 0) {
|
| + usbi_err(ITRANSFER_CTX(transfer),
|
| + "failed to read monotonic clock, errno=%d", errno);
|
| + return r;
|
| + }
|
| +
|
| + current_time.tv_sec += timeout / 1000;
|
| + current_time.tv_nsec += (timeout % 1000) * 1000000;
|
| +
|
| + if (current_time.tv_nsec > 1000000000) {
|
| + current_time.tv_nsec -= 1000000000;
|
| + current_time.tv_sec++;
|
| + }
|
| +
|
| + TIMESPEC_TO_TIMEVAL(&transfer->timeout, ¤t_time);
|
| + return 0;
|
| +}
|
| +
|
| +/* add a transfer to the (timeout-sorted) active transfers list.
|
| + * returns 1 if the transfer has a timeout and it is the timeout next to
|
| + * expire */
|
| +static int add_to_flying_list(struct usbi_transfer *transfer)
|
| +{
|
| + struct usbi_transfer *cur;
|
| + struct timeval *timeout = &transfer->timeout;
|
| + struct libusb_context *ctx = ITRANSFER_CTX(transfer);
|
| + int r = 0;
|
| + int first = 1;
|
| +
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| +
|
| + /* if we have no other flying transfers, start the list with this one */
|
| + if (list_empty(&ctx->flying_transfers)) {
|
| + list_add(&transfer->list, &ctx->flying_transfers);
|
| + if (timerisset(timeout))
|
| + r = 1;
|
| + goto out;
|
| + }
|
| +
|
| + /* if we have infinite timeout, append to end of list */
|
| + if (!timerisset(timeout)) {
|
| + list_add_tail(&transfer->list, &ctx->flying_transfers);
|
| + goto out;
|
| + }
|
| +
|
| + /* otherwise, find appropriate place in list */
|
| + list_for_each_entry(cur, &ctx->flying_transfers, list, struct usbi_transfer) {
|
| + /* find first timeout that occurs after the transfer in question */
|
| + struct timeval *cur_tv = &cur->timeout;
|
| +
|
| + if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
|
| + (cur_tv->tv_sec == timeout->tv_sec &&
|
| + cur_tv->tv_usec > timeout->tv_usec)) {
|
| + list_add_tail(&transfer->list, &cur->list);
|
| + r = first;
|
| + goto out;
|
| + }
|
| + first = 0;
|
| + }
|
| +
|
| + /* otherwise we need to be inserted at the end */
|
| + list_add_tail(&transfer->list, &ctx->flying_transfers);
|
| +out:
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| + return r;
|
| +}
|
| +
|
| +/** \ingroup asyncio
|
| + * Allocate a libusb transfer with a specified number of isochronous packet
|
| + * descriptors. The returned transfer is pre-initialized for you. When the new
|
| + * transfer is no longer needed, it should be freed with
|
| + * libusb_free_transfer().
|
| + *
|
| + * Transfers intended for non-isochronous endpoints (e.g. control, bulk,
|
| + * interrupt) should specify an iso_packets count of zero.
|
| + *
|
| + * For transfers intended for isochronous endpoints, specify an appropriate
|
| + * number of packet descriptors to be allocated as part of the transfer.
|
| + * The returned transfer is not specially initialized for isochronous I/O;
|
| + * you are still required to set the
|
| + * \ref libusb_transfer::num_iso_packets "num_iso_packets" and
|
| + * \ref libusb_transfer::type "type" fields accordingly.
|
| + *
|
| + * It is safe to allocate a transfer with some isochronous packets and then
|
| + * use it on a non-isochronous endpoint. If you do this, ensure that at time
|
| + * of submission, num_iso_packets is 0 and that type is set appropriately.
|
| + *
|
| + * \param iso_packets number of isochronous packet descriptors to allocate
|
| + * \returns a newly allocated transfer, or NULL on error
|
| + */
|
| +DEFAULT_VISIBILITY
|
| +struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer(
|
| + int iso_packets)
|
| +{
|
| + size_t os_alloc_size = usbi_backend->transfer_priv_size
|
| + + (usbi_backend->add_iso_packet_size * iso_packets);
|
| + size_t alloc_size = sizeof(struct usbi_transfer)
|
| + + sizeof(struct libusb_transfer)
|
| + + (sizeof(struct libusb_iso_packet_descriptor) * iso_packets)
|
| + + os_alloc_size;
|
| + struct usbi_transfer *itransfer = malloc(alloc_size);
|
| + if (!itransfer)
|
| + return NULL;
|
| +
|
| + memset(itransfer, 0, alloc_size);
|
| + itransfer->num_iso_packets = iso_packets;
|
| + usbi_mutex_init(&itransfer->lock, NULL);
|
| + return USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
|
| +}
|
| +
|
| +/** \ingroup asyncio
|
| + * Free a transfer structure. This should be called for all transfers
|
| + * allocated with libusb_alloc_transfer().
|
| + *
|
| + * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
|
| + * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
|
| + * non-NULL, this function will also free the transfer buffer using the
|
| + * standard system memory allocator (e.g. free()).
|
| + *
|
| + * It is legal to call this function with a NULL transfer. In this case,
|
| + * the function will simply return safely.
|
| + *
|
| + * It is not legal to free an active transfer (one which has been submitted
|
| + * and has not yet completed).
|
| + *
|
| + * \param transfer the transfer to free
|
| + */
|
| +void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer)
|
| +{
|
| + struct usbi_transfer *itransfer;
|
| + if (!transfer)
|
| + return;
|
| +
|
| + if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
|
| + free(transfer->buffer);
|
| +
|
| + itransfer = LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
|
| + usbi_mutex_destroy(&itransfer->lock);
|
| + free(itransfer);
|
| +}
|
| +
|
| +/** \ingroup asyncio
|
| + * Submit a transfer. This function will fire off the USB transfer and then
|
| + * return immediately.
|
| + *
|
| + * \param transfer the transfer to submit
|
| + * \returns 0 on success
|
| + * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
|
| + * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted.
|
| + * \returns another LIBUSB_ERROR code on other failure
|
| + */
|
| +int API_EXPORTED libusb_submit_transfer(struct libusb_transfer *transfer)
|
| +{
|
| + struct libusb_context *ctx = TRANSFER_CTX(transfer);
|
| + struct usbi_transfer *itransfer =
|
| + LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
|
| + int r;
|
| + int first;
|
| +
|
| + usbi_mutex_lock(&itransfer->lock);
|
| + itransfer->transferred = 0;
|
| + itransfer->flags = 0;
|
| + r = calculate_timeout(itransfer);
|
| + if (r < 0) {
|
| + r = LIBUSB_ERROR_OTHER;
|
| + goto out;
|
| + }
|
| +
|
| + first = add_to_flying_list(itransfer);
|
| + r = usbi_backend->submit_transfer(itransfer);
|
| + if (r) {
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| + list_del(&itransfer->list);
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| + }
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| + else if (first && usbi_using_timerfd(ctx)) {
|
| + /* if this transfer has the lowest timeout of all active transfers,
|
| + * rearm the timerfd with this transfer's timeout */
|
| + const struct itimerspec it = { {0, 0},
|
| + { itransfer->timeout.tv_sec, itransfer->timeout.tv_usec * 1000 } };
|
| + usbi_dbg("arm timerfd for timeout in %dms (first in line)", transfer->timeout);
|
| + r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
|
| + if (r < 0)
|
| + r = LIBUSB_ERROR_OTHER;
|
| + }
|
| +#else
|
| + (void)first;
|
| +#endif
|
| +
|
| +out:
|
| + usbi_mutex_unlock(&itransfer->lock);
|
| + return r;
|
| +}
|
| +
|
| +/** \ingroup asyncio
|
| + * Asynchronously cancel a previously submitted transfer.
|
| + * This function returns immediately, but this does not indicate cancellation
|
| + * is complete. Your callback function will be invoked at some later time
|
| + * with a transfer status of
|
| + * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
|
| + * "LIBUSB_TRANSFER_CANCELLED."
|
| + *
|
| + * \param transfer the transfer to cancel
|
| + * \returns 0 on success
|
| + * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is already complete or
|
| + * cancelled.
|
| + * \returns a LIBUSB_ERROR code on failure
|
| + */
|
| +int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer)
|
| +{
|
| + struct usbi_transfer *itransfer =
|
| + LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
|
| + int r;
|
| +
|
| + usbi_dbg("");
|
| + usbi_mutex_lock(&itransfer->lock);
|
| + r = usbi_backend->cancel_transfer(itransfer);
|
| + if (r < 0) {
|
| + usbi_err(TRANSFER_CTX(transfer),
|
| + "cancel transfer failed error %d", r);
|
| +
|
| + if (r == LIBUSB_ERROR_NO_DEVICE)
|
| + itransfer->flags |= USBI_TRANSFER_DEVICE_DISAPPEARED;
|
| + }
|
| +
|
| + itransfer->flags |= USBI_TRANSFER_CANCELLING;
|
| +
|
| + usbi_mutex_unlock(&itransfer->lock);
|
| + return r;
|
| +}
|
| +
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| +static int disarm_timerfd(struct libusb_context *ctx)
|
| +{
|
| + const struct itimerspec disarm_timer = { { 0, 0 }, { 0, 0 } };
|
| + int r;
|
| +
|
| + usbi_dbg("");
|
| + r = timerfd_settime(ctx->timerfd, 0, &disarm_timer, NULL);
|
| + if (r < 0)
|
| + return LIBUSB_ERROR_OTHER;
|
| + else
|
| + return 0;
|
| +}
|
| +
|
| +/* iterates through the flying transfers, and rearms the timerfd based on the
|
| + * next upcoming timeout.
|
| + * must be called with flying_list locked.
|
| + * returns 0 if there was no timeout to arm, 1 if the next timeout was armed,
|
| + * or a LIBUSB_ERROR code on failure.
|
| + */
|
| +static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
|
| +{
|
| + struct usbi_transfer *transfer;
|
| +
|
| + list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
|
| + struct timeval *cur_tv = &transfer->timeout;
|
| +
|
| + /* if we've reached transfers of infinite timeout, then we have no
|
| + * arming to do */
|
| + if (!timerisset(cur_tv))
|
| + return 0;
|
| +
|
| + /* act on first transfer that is not already cancelled */
|
| + if (!(transfer->flags & USBI_TRANSFER_TIMED_OUT)) {
|
| + int r;
|
| + const struct itimerspec it = { {0, 0},
|
| + { cur_tv->tv_sec, cur_tv->tv_usec * 1000 } };
|
| + usbi_dbg("next timeout originally %dms", USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
|
| + r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
|
| + if (r < 0)
|
| + return LIBUSB_ERROR_OTHER;
|
| + return 1;
|
| + }
|
| + }
|
| +
|
| + return 0;
|
| +}
|
| +#else
|
| +static int disarm_timerfd(struct libusb_context *ctx)
|
| +{
|
| + (void)ctx;
|
| + return 0;
|
| +}
|
| +static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
|
| +{
|
| + (void)ctx;
|
| + return 0;
|
| +}
|
| +#endif
|
| +
|
| +/* Handle completion of a transfer (completion might be an error condition).
|
| + * This will invoke the user-supplied callback function, which may end up
|
| + * freeing the transfer. Therefore you cannot use the transfer structure
|
| + * after calling this function, and you should free all backend-specific
|
| + * data before calling it.
|
| + * Do not call this function with the usbi_transfer lock held. User-specified
|
| + * callback functions may attempt to directly resubmit the transfer, which
|
| + * will attempt to take the lock. */
|
| +int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
|
| + enum libusb_transfer_status status)
|
| +{
|
| + struct libusb_transfer *transfer =
|
| + USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
|
| + struct libusb_context *ctx = TRANSFER_CTX(transfer);
|
| + uint8_t flags;
|
| + int r;
|
| +
|
| + /* FIXME: could be more intelligent with the timerfd here. we don't need
|
| + * to disarm the timerfd if there was no timer running, and we only need
|
| + * to rearm the timerfd if the transfer that expired was the one with
|
| + * the shortest timeout. */
|
| +
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| + list_del(&itransfer->list);
|
| + r = arm_timerfd_for_next_timeout(ctx);
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| +
|
| + if (r < 0) {
|
| + return r;
|
| + } else if (r == 0) {
|
| + r = disarm_timerfd(ctx);
|
| + if (r < 0)
|
| + return r;
|
| + }
|
| +
|
| + if (status == LIBUSB_TRANSFER_COMPLETED
|
| + && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
|
| + int rqlen = transfer->length;
|
| + if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL)
|
| + rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
|
| + if (rqlen != itransfer->transferred) {
|
| + usbi_dbg("interpreting short transfer as error");
|
| + status = LIBUSB_TRANSFER_ERROR;
|
| + }
|
| + }
|
| +
|
| + flags = transfer->flags;
|
| + transfer->status = status;
|
| + transfer->actual_length = itransfer->transferred;
|
| + if (transfer->callback)
|
| + transfer->callback(transfer);
|
| + /* transfer might have been freed by the above call, do not use from
|
| + * this point. */
|
| + if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
|
| + libusb_free_transfer(transfer);
|
| + usbi_mutex_lock(&ctx->event_waiters_lock);
|
| + usbi_cond_broadcast(&ctx->event_waiters_cond);
|
| + usbi_mutex_unlock(&ctx->event_waiters_lock);
|
| + return 0;
|
| +}
|
| +
|
| +/* Similar to usbi_handle_transfer_completion() but exclusively for transfers
|
| + * that were asynchronously cancelled. The same concerns w.r.t. freeing of
|
| + * transfers exist here.
|
| + * Do not call this function with the usbi_transfer lock held. User-specified
|
| + * callback functions may attempt to directly resubmit the transfer, which
|
| + * will attempt to take the lock. */
|
| +int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
|
| +{
|
| + /* if the URB was cancelled due to timeout, report timeout to the user */
|
| + if (transfer->flags & USBI_TRANSFER_TIMED_OUT) {
|
| + usbi_dbg("detected timeout cancellation");
|
| + return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
|
| + }
|
| +
|
| + /* otherwise its a normal async cancel */
|
| + return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Attempt to acquire the event handling lock. This lock is used to ensure that
|
| + * only one thread is monitoring libusb event sources at any one time.
|
| + *
|
| + * You only need to use this lock if you are developing an application
|
| + * which calls poll() or select() on libusb's file descriptors directly.
|
| + * If you stick to libusb's event handling loop functions (e.g.
|
| + * libusb_handle_events()) then you do not need to be concerned with this
|
| + * locking.
|
| + *
|
| + * While holding this lock, you are trusted to actually be handling events.
|
| + * If you are no longer handling events, you must call libusb_unlock_events()
|
| + * as soon as possible.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \returns 0 if the lock was obtained successfully
|
| + * \returns 1 if the lock was not obtained (i.e. another thread holds the lock)
|
| + * \see \ref mtasync
|
| + */
|
| +int API_EXPORTED libusb_try_lock_events(libusb_context *ctx)
|
| +{
|
| + int r;
|
| + USBI_GET_CONTEXT(ctx);
|
| +
|
| + /* is someone else waiting to modify poll fds? if so, don't let this thread
|
| + * start event handling */
|
| + usbi_mutex_lock(&ctx->pollfd_modify_lock);
|
| + r = ctx->pollfd_modify;
|
| + usbi_mutex_unlock(&ctx->pollfd_modify_lock);
|
| + if (r) {
|
| + usbi_dbg("someone else is modifying poll fds");
|
| + return 1;
|
| + }
|
| +
|
| + r = usbi_mutex_trylock(&ctx->events_lock);
|
| + if (r)
|
| + return 1;
|
| +
|
| + ctx->event_handler_active = 1;
|
| + return 0;
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Acquire the event handling lock, blocking until successful acquisition if
|
| + * it is contended. This lock is used to ensure that only one thread is
|
| + * monitoring libusb event sources at any one time.
|
| + *
|
| + * You only need to use this lock if you are developing an application
|
| + * which calls poll() or select() on libusb's file descriptors directly.
|
| + * If you stick to libusb's event handling loop functions (e.g.
|
| + * libusb_handle_events()) then you do not need to be concerned with this
|
| + * locking.
|
| + *
|
| + * While holding this lock, you are trusted to actually be handling events.
|
| + * If you are no longer handling events, you must call libusb_unlock_events()
|
| + * as soon as possible.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \see \ref mtasync
|
| + */
|
| +void API_EXPORTED libusb_lock_events(libusb_context *ctx)
|
| +{
|
| + USBI_GET_CONTEXT(ctx);
|
| + usbi_mutex_lock(&ctx->events_lock);
|
| + ctx->event_handler_active = 1;
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Release the lock previously acquired with libusb_try_lock_events() or
|
| + * libusb_lock_events(). Releasing this lock will wake up any threads blocked
|
| + * on libusb_wait_for_event().
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \see \ref mtasync
|
| + */
|
| +void API_EXPORTED libusb_unlock_events(libusb_context *ctx)
|
| +{
|
| + USBI_GET_CONTEXT(ctx);
|
| + ctx->event_handler_active = 0;
|
| + usbi_mutex_unlock(&ctx->events_lock);
|
| +
|
| + /* FIXME: perhaps we should be a bit more efficient by not broadcasting
|
| + * the availability of the events lock when we are modifying pollfds
|
| + * (check ctx->pollfd_modify)? */
|
| + usbi_mutex_lock(&ctx->event_waiters_lock);
|
| + usbi_cond_broadcast(&ctx->event_waiters_cond);
|
| + usbi_mutex_unlock(&ctx->event_waiters_lock);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Determine if it is still OK for this thread to be doing event handling.
|
| + *
|
| + * Sometimes, libusb needs to temporarily pause all event handlers, and this
|
| + * is the function you should use before polling file descriptors to see if
|
| + * this is the case.
|
| + *
|
| + * If this function instructs your thread to give up the events lock, you
|
| + * should just continue the usual logic that is documented in \ref mtasync.
|
| + * On the next iteration, your thread will fail to obtain the events lock,
|
| + * and will hence become an event waiter.
|
| + *
|
| + * This function should be called while the events lock is held: you don't
|
| + * need to worry about the results of this function if your thread is not
|
| + * the current event handler.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \returns 1 if event handling can start or continue
|
| + * \returns 0 if this thread must give up the events lock
|
| + * \see \ref fullstory "Multi-threaded I/O: the full story"
|
| + */
|
| +int API_EXPORTED libusb_event_handling_ok(libusb_context *ctx)
|
| +{
|
| + int r;
|
| + USBI_GET_CONTEXT(ctx);
|
| +
|
| + /* is someone else waiting to modify poll fds? if so, don't let this thread
|
| + * continue event handling */
|
| + usbi_mutex_lock(&ctx->pollfd_modify_lock);
|
| + r = ctx->pollfd_modify;
|
| + usbi_mutex_unlock(&ctx->pollfd_modify_lock);
|
| + if (r) {
|
| + usbi_dbg("someone else is modifying poll fds");
|
| + return 0;
|
| + }
|
| +
|
| + return 1;
|
| +}
|
| +
|
| +
|
| +/** \ingroup poll
|
| + * Determine if an active thread is handling events (i.e. if anyone is holding
|
| + * the event handling lock).
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \returns 1 if a thread is handling events
|
| + * \returns 0 if there are no threads currently handling events
|
| + * \see \ref mtasync
|
| + */
|
| +int API_EXPORTED libusb_event_handler_active(libusb_context *ctx)
|
| +{
|
| + int r;
|
| + USBI_GET_CONTEXT(ctx);
|
| +
|
| + /* is someone else waiting to modify poll fds? if so, don't let this thread
|
| + * start event handling -- indicate that event handling is happening */
|
| + usbi_mutex_lock(&ctx->pollfd_modify_lock);
|
| + r = ctx->pollfd_modify;
|
| + usbi_mutex_unlock(&ctx->pollfd_modify_lock);
|
| + if (r) {
|
| + usbi_dbg("someone else is modifying poll fds");
|
| + return 1;
|
| + }
|
| +
|
| + return ctx->event_handler_active;
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Acquire the event waiters lock. This lock is designed to be obtained under
|
| + * the situation where you want to be aware when events are completed, but
|
| + * some other thread is event handling so calling libusb_handle_events() is not
|
| + * allowed.
|
| + *
|
| + * You then obtain this lock, re-check that another thread is still handling
|
| + * events, then call libusb_wait_for_event().
|
| + *
|
| + * You only need to use this lock if you are developing an application
|
| + * which calls poll() or select() on libusb's file descriptors directly,
|
| + * <b>and</b> may potentially be handling events from 2 threads simultaenously.
|
| + * If you stick to libusb's event handling loop functions (e.g.
|
| + * libusb_handle_events()) then you do not need to be concerned with this
|
| + * locking.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \see \ref mtasync
|
| + */
|
| +void API_EXPORTED libusb_lock_event_waiters(libusb_context *ctx)
|
| +{
|
| + USBI_GET_CONTEXT(ctx);
|
| + usbi_mutex_lock(&ctx->event_waiters_lock);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Release the event waiters lock.
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \see \ref mtasync
|
| + */
|
| +void API_EXPORTED libusb_unlock_event_waiters(libusb_context *ctx)
|
| +{
|
| + USBI_GET_CONTEXT(ctx);
|
| + usbi_mutex_unlock(&ctx->event_waiters_lock);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Wait for another thread to signal completion of an event. Must be called
|
| + * with the event waiters lock held, see libusb_lock_event_waiters().
|
| + *
|
| + * This function will block until any of the following conditions are met:
|
| + * -# The timeout expires
|
| + * -# A transfer completes
|
| + * -# A thread releases the event handling lock through libusb_unlock_events()
|
| + *
|
| + * Condition 1 is obvious. Condition 2 unblocks your thread <em>after</em>
|
| + * the callback for the transfer has completed. Condition 3 is important
|
| + * because it means that the thread that was previously handling events is no
|
| + * longer doing so, so if any events are to complete, another thread needs to
|
| + * step up and start event handling.
|
| + *
|
| + * This function releases the event waiters lock before putting your thread
|
| + * to sleep, and reacquires the lock as it is being woken up.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \param tv maximum timeout for this blocking function. A NULL value
|
| + * indicates unlimited timeout.
|
| + * \returns 0 after a transfer completes or another thread stops event handling
|
| + * \returns 1 if the timeout expired
|
| + * \see \ref mtasync
|
| + */
|
| +int API_EXPORTED libusb_wait_for_event(libusb_context *ctx, struct timeval *tv)
|
| +{
|
| + struct timespec timeout;
|
| + int r;
|
| +
|
| + USBI_GET_CONTEXT(ctx);
|
| + if (tv == NULL) {
|
| + usbi_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock);
|
| + return 0;
|
| + }
|
| +
|
| + r = usbi_backend->clock_gettime(USBI_CLOCK_REALTIME, &timeout);
|
| + if (r < 0) {
|
| + usbi_err(ctx, "failed to read realtime clock, error %d", errno);
|
| + return LIBUSB_ERROR_OTHER;
|
| + }
|
| +
|
| + timeout.tv_sec += tv->tv_sec;
|
| + timeout.tv_nsec += tv->tv_usec * 1000;
|
| + if (timeout.tv_nsec > 1000000000) {
|
| + timeout.tv_nsec -= 1000000000;
|
| + timeout.tv_sec++;
|
| + }
|
| +
|
| + r = usbi_cond_timedwait(&ctx->event_waiters_cond,
|
| + &ctx->event_waiters_lock, &timeout);
|
| + return (r == ETIMEDOUT);
|
| +}
|
| +
|
| +static void handle_timeout(struct usbi_transfer *itransfer)
|
| +{
|
| + struct libusb_transfer *transfer =
|
| + USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
|
| + int r;
|
| +
|
| + itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
|
| + r = libusb_cancel_transfer(transfer);
|
| + if (r < 0)
|
| + usbi_warn(TRANSFER_CTX(transfer),
|
| + "async cancel failed %d errno=%d", r, errno);
|
| +}
|
| +
|
| +static int handle_timeouts_locked(struct libusb_context *ctx)
|
| +{
|
| + int r;
|
| + struct timespec systime_ts;
|
| + struct timeval systime;
|
| + struct usbi_transfer *transfer;
|
| +
|
| + if (list_empty(&ctx->flying_transfers))
|
| + return 0;
|
| +
|
| + /* get current time */
|
| + r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &systime_ts);
|
| + if (r < 0)
|
| + return r;
|
| +
|
| + TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
|
| +
|
| + /* iterate through flying transfers list, finding all transfers that
|
| + * have expired timeouts */
|
| + list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
|
| + struct timeval *cur_tv = &transfer->timeout;
|
| +
|
| + /* if we've reached transfers of infinite timeout, we're all done */
|
| + if (!timerisset(cur_tv))
|
| + return 0;
|
| +
|
| + /* ignore timeouts we've already handled */
|
| + if (transfer->flags & (USBI_TRANSFER_TIMED_OUT | 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))
|
| + return 0;
|
| +
|
| + /* otherwise, we've got an expired timeout to handle */
|
| + handle_timeout(transfer);
|
| + }
|
| + return 0;
|
| +}
|
| +
|
| +static int handle_timeouts(struct libusb_context *ctx)
|
| +{
|
| + int r;
|
| + USBI_GET_CONTEXT(ctx);
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| + r = handle_timeouts_locked(ctx);
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| + return r;
|
| +}
|
| +
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| +static int handle_timerfd_trigger(struct libusb_context *ctx)
|
| +{
|
| + int r;
|
| +
|
| + r = disarm_timerfd(ctx);
|
| + if (r < 0)
|
| + return r;
|
| +
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| +
|
| + /* process the timeout that just happened */
|
| + r = handle_timeouts_locked(ctx);
|
| + if (r < 0)
|
| + goto out;
|
| +
|
| + /* arm for next timeout*/
|
| + r = arm_timerfd_for_next_timeout(ctx);
|
| +
|
| +out:
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| + return r;
|
| +}
|
| +#endif
|
| +
|
| +/* do the actual event handling. assumes that no other thread is concurrently
|
| + * doing the same thing. */
|
| +static int handle_events(struct libusb_context *ctx, struct timeval *tv)
|
| +{
|
| + int r;
|
| + struct usbi_pollfd *ipollfd;
|
| + POLL_NFDS_TYPE nfds = 0;
|
| + struct pollfd *fds;
|
| + int i = -1;
|
| + int timeout_ms;
|
| +
|
| + usbi_mutex_lock(&ctx->pollfds_lock);
|
| + list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd)
|
| + nfds++;
|
| +
|
| + /* TODO: malloc when number of fd's changes, not on every poll */
|
| + fds = malloc(sizeof(*fds) * nfds);
|
| + if (!fds) {
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| + return LIBUSB_ERROR_NO_MEM;
|
| + }
|
| +
|
| + list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd) {
|
| + struct libusb_pollfd *pollfd = &ipollfd->pollfd;
|
| + int fd = pollfd->fd;
|
| + i++;
|
| + fds[i].fd = fd;
|
| + fds[i].events = pollfd->events;
|
| + fds[i].revents = 0;
|
| + }
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| +
|
| + timeout_ms = (tv->tv_sec * 1000) + (tv->tv_usec / 1000);
|
| +
|
| + /* round up to next millisecond */
|
| + if (tv->tv_usec % 1000)
|
| + timeout_ms++;
|
| +
|
| + usbi_dbg("poll() %d fds with timeout in %dms", nfds, timeout_ms);
|
| + r = usbi_poll(fds, nfds, timeout_ms);
|
| + usbi_dbg("poll() returned %d", r);
|
| + if (r == 0) {
|
| + free(fds);
|
| + return handle_timeouts(ctx);
|
| + } else if (r == -1 && errno == EINTR) {
|
| + free(fds);
|
| + return LIBUSB_ERROR_INTERRUPTED;
|
| + } else if (r < 0) {
|
| + free(fds);
|
| + usbi_err(ctx, "poll failed %d err=%d\n", r, errno);
|
| + return LIBUSB_ERROR_IO;
|
| + }
|
| +
|
| + /* fd[0] is always the ctrl pipe */
|
| + if (fds[0].revents) {
|
| + /* another thread wanted to interrupt event handling, and it succeeded!
|
| + * handle any other events that cropped up at the same time, and
|
| + * simply return */
|
| + usbi_dbg("caught a fish on the control pipe");
|
| +
|
| + if (r == 1) {
|
| + r = 0;
|
| + goto handled;
|
| + } else {
|
| + /* prevent OS backend from trying to handle events on ctrl pipe */
|
| + fds[0].revents = 0;
|
| + r--;
|
| + }
|
| + }
|
| +
|
| +#ifdef USBI_TIMERFD_AVAILABLE
|
| + /* on timerfd configurations, fds[1] is the timerfd */
|
| + if (usbi_using_timerfd(ctx) && fds[1].revents) {
|
| + /* timerfd indicates that a timeout has expired */
|
| + int ret;
|
| + usbi_dbg("timerfd triggered");
|
| +
|
| + ret = handle_timerfd_trigger(ctx);
|
| + if (ret < 0) {
|
| + /* return error code */
|
| + r = ret;
|
| + goto handled;
|
| + } else if (r == 1) {
|
| + /* no more active file descriptors, nothing more to do */
|
| + r = 0;
|
| + goto handled;
|
| + } else {
|
| + /* more events pending...
|
| + * prevent OS backend from trying to handle events on timerfd */
|
| + fds[1].revents = 0;
|
| + r--;
|
| + }
|
| + }
|
| +#endif
|
| +
|
| + r = usbi_backend->handle_events(ctx, fds, nfds, r);
|
| + if (r)
|
| + usbi_err(ctx, "backend handle_events failed with error %d", r);
|
| +
|
| +handled:
|
| + free(fds);
|
| + return r;
|
| +}
|
| +
|
| +/* returns the smallest of:
|
| + * 1. timeout of next URB
|
| + * 2. user-supplied timeout
|
| + * returns 1 if there is an already-expired timeout, otherwise returns 0
|
| + * and populates out
|
| + */
|
| +static int get_next_timeout(libusb_context *ctx, struct timeval *tv,
|
| + struct timeval *out)
|
| +{
|
| + struct timeval timeout;
|
| + int r = libusb_get_next_timeout(ctx, &timeout);
|
| + if (r) {
|
| + /* timeout already expired? */
|
| + if (!timerisset(&timeout))
|
| + return 1;
|
| +
|
| + /* choose the smallest of next URB timeout or user specified timeout */
|
| + if (timercmp(&timeout, tv, <))
|
| + *out = timeout;
|
| + else
|
| + *out = *tv;
|
| + } else {
|
| + *out = *tv;
|
| + }
|
| + return 0;
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Handle any pending events.
|
| + *
|
| + * libusb determines "pending events" by checking if any timeouts have expired
|
| + * and by checking the set of file descriptors for activity.
|
| + *
|
| + * If a zero timeval is passed, this function will handle any already-pending
|
| + * events and then immediately return in non-blocking style.
|
| + *
|
| + * If a non-zero timeval is passed and no events are currently pending, this
|
| + * function will block waiting for events to handle up until the specified
|
| + * timeout. If an event arrives or a signal is raised, this function will
|
| + * return early.
|
| + *
|
| + * 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 pthread 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
|
| + */
|
| +int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx,
|
| + struct timeval *tv)
|
| +{
|
| + return libusb_handle_events_timeout_completed(ctx, tv, NULL);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Handle any pending events in blocking mode. There is currently a timeout
|
| + * hardcoded at 60 seconds but we plan to make it unlimited in future. For
|
| + * finer control over whether this function is blocking or non-blocking, or
|
| + * for control over the timeout, use libusb_handle_events_timeout_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.
|
| + *
|
| + * 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
|
| + */
|
| +int API_EXPORTED libusb_handle_events_completed(libusb_context *ctx,
|
| + int *completed)
|
| +{
|
| + struct timeval tv;
|
| + tv.tv_sec = 60;
|
| + tv.tv_usec = 0;
|
| + return libusb_handle_events_timeout_completed(ctx, &tv, completed);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Handle any pending events by polling file descriptors, without checking if
|
| + * any other threads are already doing so. Must be called with the event lock
|
| + * held, see libusb_lock_events().
|
| + *
|
| + * This function is designed to be called under the situation where you have
|
| + * taken the event lock and are calling poll()/select() directly on libusb's
|
| + * file descriptors (as opposed to using libusb_handle_events() or similar).
|
| + * You detect events on libusb's descriptors, so you then call this function
|
| + * with a zero timeout value (while still holding the event lock).
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \param tv the maximum time to block waiting for events, or zero for
|
| + * non-blocking mode
|
| + * \returns 0 on success, or a LIBUSB_ERROR code on failure
|
| + * \see \ref mtasync
|
| + */
|
| +int API_EXPORTED libusb_handle_events_locked(libusb_context *ctx,
|
| + struct timeval *tv)
|
| +{
|
| + int r;
|
| + struct timeval poll_timeout;
|
| +
|
| + USBI_GET_CONTEXT(ctx);
|
| + r = get_next_timeout(ctx, tv, &poll_timeout);
|
| + if (r) {
|
| + /* timeout already expired */
|
| + return handle_timeouts(ctx);
|
| + }
|
| +
|
| + return handle_events(ctx, &poll_timeout);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Determines whether your application must apply special timing considerations
|
| + * when monitoring libusb's file descriptors.
|
| + *
|
| + * This function is only useful for applications which retrieve and poll
|
| + * libusb's file descriptors in their own main loop (\ref pollmain).
|
| + *
|
| + * Ordinarily, libusb's event handler needs to be called into at specific
|
| + * moments in time (in addition to times when there is activity on the file
|
| + * descriptor set). The usual approach is to use libusb_get_next_timeout()
|
| + * to learn about when the next timeout occurs, and to adjust your
|
| + * poll()/select() timeout accordingly so that you can make a call into the
|
| + * library at that time.
|
| + *
|
| + * Some platforms supported by libusb do not come with this baggage - any
|
| + * events relevant to timing will be represented by activity on the file
|
| + * descriptor set, and libusb_get_next_timeout() will always return 0.
|
| + * This function allows you to detect whether you are running on such a
|
| + * platform.
|
| + *
|
| + * Since v1.0.5.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \returns 0 if you must call into libusb at times determined by
|
| + * libusb_get_next_timeout(), or 1 if all timeout events are handled internally
|
| + * or through regular activity on the file descriptors.
|
| + * \see \ref pollmain "Polling libusb file descriptors for event handling"
|
| + */
|
| +int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx)
|
| +{
|
| +#if defined(USBI_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 libusb needs to handle. You only
|
| + * need to use this function if you are calling poll() or select() or similar
|
| + * on libusb's file descriptors yourself - you do not need to use it if you
|
| + * are calling libusb_handle_events() or a variant directly.
|
| + *
|
| + * You should call this function in your main loop in order to determine how
|
| + * long to wait for select() or poll() to return results. libusb needs to be
|
| + * called into at this timeout, so you should use it as an upper bound on
|
| + * your select() or poll() call.
|
| + *
|
| + * When the timeout has expired, call into libusb_handle_events_timeout()
|
| + * (perhaps in non-blocking mode) so that libusb can handle the timeout.
|
| + *
|
| + * This function may return 1 (success) and an all-zero timeval. If this is
|
| + * the case, it indicates that libusb has a timeout that has already expired
|
| + * so you should call libusb_handle_events_timeout() or similar immediately.
|
| + * A return code of 0 indicates that there are no pending timeouts.
|
| + *
|
| + * On some platforms, this function will always returns 0 (no pending
|
| + * timeouts). See \ref polltime.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \param tv output location for a relative time against the current
|
| + * clock in which libusb must be called into in order to process timeout events
|
| + * \returns 0 if there are no pending timeouts, 1 if a timeout was returned,
|
| + * or LIBUSB_ERROR_OTHER on failure
|
| + */
|
| +int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx,
|
| + struct timeval *tv)
|
| +{
|
| + struct usbi_transfer *transfer;
|
| + struct timespec cur_ts;
|
| + struct timeval cur_tv;
|
| + struct timeval *next_timeout;
|
| + int r;
|
| + int found = 0;
|
| +
|
| + USBI_GET_CONTEXT(ctx);
|
| + if (usbi_using_timerfd(ctx))
|
| + return 0;
|
| +
|
| + usbi_mutex_lock(&ctx->flying_transfers_lock);
|
| + if (list_empty(&ctx->flying_transfers)) {
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| + usbi_dbg("no URBs, no timeout!");
|
| + return 0;
|
| + }
|
| +
|
| + /* find next transfer which hasn't already been processed as timed out */
|
| + list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
|
| + if (transfer->flags & (USBI_TRANSFER_TIMED_OUT | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
|
| + continue;
|
| +
|
| + /* no timeout for this transfer? */
|
| + if (!timerisset(&transfer->timeout))
|
| + continue;
|
| +
|
| + found = 1;
|
| + break;
|
| + }
|
| + usbi_mutex_unlock(&ctx->flying_transfers_lock);
|
| +
|
| + if (!found) {
|
| + usbi_dbg("no URB with timeout or all handled by OS; no timeout!");
|
| + return 0;
|
| + }
|
| +
|
| + next_timeout = &transfer->timeout;
|
| +
|
| + r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &cur_ts);
|
| + if (r < 0) {
|
| + usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno);
|
| + return LIBUSB_ERROR_OTHER;
|
| + }
|
| + TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
|
| +
|
| + if (!timercmp(&cur_tv, next_timeout, <)) {
|
| + usbi_dbg("first timeout already expired");
|
| + timerclear(tv);
|
| + } else {
|
| + timersub(next_timeout, &cur_tv, tv);
|
| + usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
|
| + }
|
| +
|
| + return 1;
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Register notification functions for file descriptor additions/removals.
|
| + * These functions will be invoked for every new or removed file descriptor
|
| + * that libusb uses as an event source.
|
| + *
|
| + * To remove notifiers, pass NULL values for the function pointers.
|
| + *
|
| + * Note that file descriptors may have been added even before you register
|
| + * these notifiers (e.g. at libusb_init() time).
|
| + *
|
| + * Additionally, note that the removal notifier may be called during
|
| + * libusb_exit() (e.g. when it is closing file descriptors that were opened
|
| + * and added to the poll set at libusb_init() time). If you don't want this,
|
| + * remove the notifiers immediately before calling libusb_exit().
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \param added_cb pointer to function for addition notifications
|
| + * \param removed_cb pointer to function for removal notifications
|
| + * \param user_data User data to be passed back to callbacks (useful for
|
| + * passing context information)
|
| + */
|
| +void API_EXPORTED libusb_set_pollfd_notifiers(libusb_context *ctx,
|
| + libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
|
| + void *user_data)
|
| +{
|
| + USBI_GET_CONTEXT(ctx);
|
| + ctx->fd_added_cb = added_cb;
|
| + ctx->fd_removed_cb = removed_cb;
|
| + ctx->fd_cb_user_data = user_data;
|
| +}
|
| +
|
| +/* Add a file descriptor to the list of file descriptors to be monitored.
|
| + * events should be specified as a bitmask of events passed to poll(), e.g.
|
| + * POLLIN and/or POLLOUT. */
|
| +int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events)
|
| +{
|
| + struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
|
| + if (!ipollfd)
|
| + return LIBUSB_ERROR_NO_MEM;
|
| +
|
| + usbi_dbg("add fd %d events %d", fd, events);
|
| + ipollfd->pollfd.fd = fd;
|
| + ipollfd->pollfd.events = events;
|
| + usbi_mutex_lock(&ctx->pollfds_lock);
|
| + list_add_tail(&ipollfd->list, &ctx->pollfds);
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| +
|
| + if (ctx->fd_added_cb)
|
| + ctx->fd_added_cb(fd, events, ctx->fd_cb_user_data);
|
| + return 0;
|
| +}
|
| +
|
| +/* Remove a file descriptor from the list of file descriptors to be polled. */
|
| +void usbi_remove_pollfd(struct libusb_context *ctx, int fd)
|
| +{
|
| + struct usbi_pollfd *ipollfd;
|
| + int found = 0;
|
| +
|
| + usbi_dbg("remove fd %d", fd);
|
| + usbi_mutex_lock(&ctx->pollfds_lock);
|
| + list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd)
|
| + if (ipollfd->pollfd.fd == fd) {
|
| + found = 1;
|
| + break;
|
| + }
|
| +
|
| + if (!found) {
|
| + usbi_dbg("couldn't find fd %d to remove", fd);
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| + return;
|
| + }
|
| +
|
| + list_del(&ipollfd->list);
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| + free(ipollfd);
|
| + if (ctx->fd_removed_cb)
|
| + ctx->fd_removed_cb(fd, ctx->fd_cb_user_data);
|
| +}
|
| +
|
| +/** \ingroup poll
|
| + * Retrieve a list of file descriptors that should be polled by your main loop
|
| + * as libusb event sources.
|
| + *
|
| + * The returned list is NULL-terminated and should be freed with free() when
|
| + * done. The actual list contents must not be touched.
|
| + *
|
| + * As file descriptors are a Unix-specific concept, this function is not
|
| + * available on Windows and will always return NULL.
|
| + *
|
| + * \param ctx the context to operate on, or NULL for the default context
|
| + * \returns a NULL-terminated list of libusb_pollfd structures
|
| + * \returns NULL on error
|
| + * \returns NULL on platforms where the functionality is not available
|
| + */
|
| +DEFAULT_VISIBILITY
|
| +const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
|
| + libusb_context *ctx)
|
| +{
|
| +#ifndef OS_WINDOWS
|
| + struct libusb_pollfd **ret = NULL;
|
| + struct usbi_pollfd *ipollfd;
|
| + size_t i = 0;
|
| + size_t cnt = 0;
|
| + USBI_GET_CONTEXT(ctx);
|
| +
|
| + usbi_mutex_lock(&ctx->pollfds_lock);
|
| + list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd)
|
| + cnt++;
|
| +
|
| + ret = calloc(cnt + 1, sizeof(struct libusb_pollfd *));
|
| + if (!ret)
|
| + goto out;
|
| +
|
| + list_for_each_entry(ipollfd, &ctx->pollfds, list, struct usbi_pollfd)
|
| + ret[i++] = (struct libusb_pollfd *) ipollfd;
|
| + ret[cnt] = NULL;
|
| +
|
| +out:
|
| + usbi_mutex_unlock(&ctx->pollfds_lock);
|
| + return (const struct libusb_pollfd **) ret;
|
| +#else
|
| + return NULL;
|
| +#endif
|
| +}
|
| +
|
| +/* Backends call this from handle_events to report disconnection of a device.
|
| + * The transfers get cancelled appropriately.
|
| + */
|
| +void usbi_handle_disconnect(struct libusb_device_handle *handle)
|
| +{
|
| + struct usbi_transfer *cur;
|
| + struct usbi_transfer *to_cancel;
|
| +
|
| + usbi_dbg("device %d.%d",
|
| + handle->dev->bus_number, handle->dev->device_address);
|
| +
|
| + /* terminate all pending transfers with the LIBUSB_TRANSFER_NO_DEVICE
|
| + * status code.
|
| + *
|
| + * this is a bit tricky because:
|
| + * 1. we can't do transfer completion while holding flying_transfers_lock
|
| + * 2. the transfers list can change underneath us - if we were to build a
|
| + * list of transfers to complete (while holding look), the situation
|
| + * might be different by the time we come to free them
|
| + *
|
| + * so we resort to a loop-based approach as below
|
| + * FIXME: is this still potentially racy?
|
| + */
|
| +
|
| + while (1) {
|
| + usbi_mutex_lock(&HANDLE_CTX(handle)->flying_transfers_lock);
|
| + to_cancel = NULL;
|
| + list_for_each_entry(cur, &HANDLE_CTX(handle)->flying_transfers, list, struct usbi_transfer)
|
| + if (USBI_TRANSFER_TO_LIBUSB_TRANSFER(cur)->dev_handle == handle) {
|
| + to_cancel = cur;
|
| + break;
|
| + }
|
| + usbi_mutex_unlock(&HANDLE_CTX(handle)->flying_transfers_lock);
|
| +
|
| + if (!to_cancel)
|
| + break;
|
| +
|
| + usbi_backend->clear_transfer_priv(to_cancel);
|
| + usbi_handle_transfer_completion(to_cancel, LIBUSB_TRANSFER_NO_DEVICE);
|
| + }
|
| +
|
| +}
|
|
|
Chromium Code Reviews
Issue 9826025:
Import libusb 1.0.9-rc3 into third_party (Closed)
Base URL: svn://svn.chromium.org/chrome/trunk/src