io.c

最新的libusb库

 * \param transfer the transfer to submit
 * \returns 0 on success
 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
 * \returns another LIBUSB_ERROR code on other failure
 */
API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)
{
	struct usbi_transfer *itransfer =
		__LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
	int r;

	itransfer->transferred = 0;
	r = calculate_timeout(itransfer);
	if (r < 0)
		return LIBUSB_ERROR_OTHER;

	add_to_flying_list(itransfer);
	r = usbi_backend->submit_transfer(itransfer);
	if (r) {
		pthread_mutex_lock(&TRANSFER_CTX(transfer)->flying_transfers_lock);
		list_del(&itransfer->list);
		pthread_mutex_unlock(&TRANSFER_CTX(transfer)->flying_transfers_lock);
	}

	return r;
}

/** \ingroup asyncio
 * Asynchronously cancel a previously submitted transfer.
 * It is undefined behaviour to call this function on a transfer that is
 * already being cancelled or has already completed.
 * This function returns immediately, but this does not indicate cancellation
 * is complete. Your callback function will be invoked at some later time
 * with a transfer status of
 * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
 * "LIBUSB_TRANSFER_CANCELLED."
 *
 * \param transfer the transfer to cancel
 * \returns 0 on success
 * \returns a LIBUSB_ERROR code on failure
 */
API_EXPORTED int libusb_cancel_transfer(struct libusb_transfer *transfer)
{
	struct usbi_transfer *itransfer =
		__LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
	int r;

	usbi_dbg("");
	r = usbi_backend->cancel_transfer(itransfer);
	if (r < 0)
		usbi_err(TRANSFER_CTX(transfer),
			"cancel transfer failed error %d", r);
	return r;
}

/* 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. */
void 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;

	pthread_mutex_lock(&ctx->flying_transfers_lock);
	list_del(&itransfer->list);
	pthread_mutex_unlock(&ctx->flying_transfers_lock);

	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);
	pthread_mutex_lock(&ctx->event_waiters_lock);
	pthread_cond_broadcast(&ctx->event_waiters_cond);
	pthread_mutex_unlock(&ctx->event_waiters_lock);
}

/* 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.
 */
void 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");
		usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
		return;
	}

	/* otherwise its a normal async cancel */
	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
 */
API_EXPORTED int libusb_try_lock_events(libusb_context *ctx)
{
	int r;
	USBI_GET_CONTEXT(ctx);
	
	r = pthread_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
 */
API_EXPORTED void libusb_lock_events(libusb_context *ctx)
{
	USBI_GET_CONTEXT(ctx);
	pthread_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
 */
API_EXPORTED void libusb_unlock_events(libusb_context *ctx)
{
	USBI_GET_CONTEXT(ctx);
	ctx->event_handler_active = 0;
	pthread_mutex_unlock(&ctx->events_lock);

	pthread_mutex_lock(&ctx->event_waiters_lock);
	pthread_cond_broadcast(&ctx->event_waiters_cond);
	pthread_mutex_unlock(&ctx->event_waiters_lock);
}

/** \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
 */
API_EXPORTED int libusb_event_handler_active(libusb_context *ctx)
{
	USBI_GET_CONTEXT(ctx);
	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
 */
API_EXPORTED void libusb_lock_event_waiters(libusb_context *ctx)
{
	USBI_GET_CONTEXT(ctx);
	pthread_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
 */
API_EXPORTED void libusb_unlock_event_waiters(libusb_context *ctx)
{
	USBI_GET_CONTEXT(ctx);
	pthread_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
 */
API_EXPORTED int libusb_wait_for_event(libusb_context *ctx, struct timeval *tv)
{
	struct timespec timeout;
	int r;

	USBI_GET_CONTEXT(ctx);
	if (tv == NULL) {
		pthread_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock);
		return 0;
	}

	r = clock_gettime(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 = pthread_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(struct libusb_context *ctx)
{
	struct timespec systime_ts;
	struct timeval systime;
	struct usbi_transfer *transfer;
	int r = 0;

	USBI_GET_CONTEXT(ctx);
	pthread_mutex_lock(&ctx->flying_transfers_lock);
	if (list_empty(&ctx->flying_transfers))
		goto out;

	/* get current time */
	r = clock_gettime(CLOCK_MONOTONIC, &systime_ts);
	if (r < 0)
		goto out;

	TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);

	/* iterate through flying transfers list, finding all transfers that
	 * have expired timeouts */