io.c

linux 下的libusb 1.0.0版本

	pthread_mutex_init(&ctx->flying_transfers_lock, NULL);
	pthread_mutex_init(&ctx->pollfds_lock, NULL);
	pthread_mutex_init(&ctx->pollfd_modify_lock, NULL);
	pthread_mutex_init(&ctx->events_lock, NULL);
	pthread_mutex_init(&ctx->event_waiters_lock, NULL);
	pthread_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 = pipe(ctx->ctrl_pipe);
	if (r < 0)
		return LIBUSB_ERROR_OTHER;

	r = usbi_add_pollfd(ctx, ctx->ctrl_pipe[0], POLLIN);
	if (r < 0)
		return r;

	return 0;
}

void usbi_io_exit(struct libusb_context *ctx)
{
	usbi_remove_pollfd(ctx, ctx->ctrl_pipe[0]);
	close(ctx->ctrl_pipe[0]);
	close(ctx->ctrl_pipe[1]);
}

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 = clock_gettime(CLOCK_MONOTONIC, &current_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, &current_time);
	return 0;
}

static void add_to_flying_list(struct usbi_transfer *transfer)
{
	struct usbi_transfer *cur;
	struct timeval *timeout = &transfer->timeout;
	struct libusb_context *ctx = ITRANSFER_CTX(transfer);
	
	pthread_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);
		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) {
		/* 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);
			goto out;
		}
	}

	/* otherwise we need to be inserted at the end */
	list_add_tail(&transfer->list, &ctx->flying_transfers);
out:
	pthread_mutex_unlock(&ctx->flying_transfers_lock);
}

/** \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
 */
API_EXPORTED struct libusb_transfer *libusb_alloc_transfer(int iso_packets)
{
	size_t os_alloc_size = usbi_backend->transfer_priv_size
		+ (usbi_backend->add_iso_packet_size * iso_packets);
	int alloc_size = sizeof(struct usbi_transfer)
		+ 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;
	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.
 *
 * \param transfer the transfer to free
 */
API_EXPORTED void 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);
	free(itransfer);
}

/** \ingroup asyncio
 * Submit a transfer. This function will fire off the USB transfer and then
 * return immediately.
 *
 * It is undefined behaviour to submit a transfer that has already been
 * submitted but has not yet completed.
 *
 * \param transfer the transfer to submit
 * \returns 0 on success
 * \returns 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;
	itransfer->flags = 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);

	/* is someone else waiting to modify poll fds? if so, don't let this thread
	 * start event handling */
	pthread_mutex_lock(&ctx->pollfd_modify_lock);