core.c

linux 下的libusb 1.0.0版本

 * \returns 0 on success
 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
 * \returns another LIBUSB_ERROR code on other failure
 */
API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
{
	struct libusb_context *ctx = DEVICE_CTX(dev);
	struct libusb_device_handle *_handle;
	size_t priv_size = usbi_backend->device_handle_priv_size;
	unsigned char dummy = 1;
	int r;
	usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);

	_handle = malloc(sizeof(*_handle) + priv_size);
	if (!_handle)
		return LIBUSB_ERROR_NO_MEM;

	r = pthread_mutex_init(&_handle->lock, NULL);
	if (r)
		return LIBUSB_ERROR_OTHER;

	_handle->dev = libusb_ref_device(dev);
	_handle->claimed_interfaces = 0;
	memset(&_handle->os_priv, 0, priv_size);

	r = usbi_backend->open(_handle);
	if (r < 0) {
		libusb_unref_device(dev);
		free(_handle);
		return r;
	}

	pthread_mutex_lock(&ctx->open_devs_lock);
	list_add(&_handle->list, &ctx->open_devs);
	pthread_mutex_unlock(&ctx->open_devs_lock);
	*handle = _handle;


	/* At this point, we want to interrupt any existing event handlers so
	 * that they realise the addition of the new device's poll fd. One
	 * example when this is desirable is if the user is running a separate
	 * dedicated libusb events handling thread, which is running with a long
	 * or infinite timeout. We want to interrupt that iteration of the loop,
	 * so that it picks up the new fd, and then continues. */

	/* record that we are messing with poll fds */
	pthread_mutex_lock(&ctx->pollfd_modify_lock);
	ctx->pollfd_modify++;
	pthread_mutex_unlock(&ctx->pollfd_modify_lock);

	/* write some data on control pipe to interrupt event handlers */
	r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
	if (r <= 0) {
		usbi_warn(ctx, "internal signalling write failed");
		pthread_mutex_lock(&ctx->pollfd_modify_lock);
		ctx->pollfd_modify--;
		pthread_mutex_unlock(&ctx->pollfd_modify_lock);
		return 0;
	}

	/* take event handling lock */
	libusb_lock_events(ctx);

	/* read the dummy data */
	r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
	if (r <= 0)
		usbi_warn(ctx, "internal signalling read failed");

	/* we're done with modifying poll fds */
	pthread_mutex_lock(&ctx->pollfd_modify_lock);
	ctx->pollfd_modify--;
	pthread_mutex_unlock(&ctx->pollfd_modify_lock);

	/* Release event handling lock and wake up event waiters */
	libusb_unlock_events(ctx);

	return 0;
}

/** \ingroup dev
 * Convenience function for finding a device with a particular
 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
 * for those scenarios where you are using libusb to knock up a quick test
 * application - it allows you to avoid calling libusb_get_device_list() and
 * worrying about traversing/freeing the list.
 *
 * This function has limitations and is hence not intended for use in real
 * applications: if multiple devices have the same IDs it will only
 * give you the first one, etc.
 *
 * \param ctx the context to operate on, or NULL for the default context
 * \param vendor_id the idVendor value to search for
 * \param product_id the idProduct value to search for
 * \returns a handle for the first found device, or NULL on error or if the
 * device could not be found. */
API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
	libusb_context *ctx, uint16_t vendor_id, uint16_t product_id)
{
	struct libusb_device **devs;
	struct libusb_device *found = NULL;
	struct libusb_device *dev;
	struct libusb_device_handle *handle = NULL;
	size_t i = 0;
	int r;

	if (libusb_get_device_list(ctx, &devs) < 0)
		return NULL;

	while ((dev = devs[i++]) != NULL) {
		struct libusb_device_descriptor desc;
		r = libusb_get_device_descriptor(dev, &desc);
		if (r < 0)
			goto out;
		if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
			found = dev;
			break;
		}
	}

	if (found) {
		r = libusb_open(found, &handle);
		if (r < 0)
			handle = NULL;
	}

out:
	libusb_free_device_list(devs, 1);
	return handle;
}

static void do_close(struct libusb_context *ctx,
	struct libusb_device_handle *dev_handle)
{
	pthread_mutex_lock(&ctx->open_devs_lock);
	list_del(&dev_handle->list);
	pthread_mutex_unlock(&ctx->open_devs_lock);

	usbi_backend->close(dev_handle);
	libusb_unref_device(dev_handle->dev);
	free(dev_handle);
}

/** \ingroup dev
 * Close a device handle. Should be called on all open handles before your
 * application exits.
 *
 * Internally, this function destroys the reference that was added by
 * libusb_open() on the given device.
 *
 * This is a non-blocking function; no requests are sent over the bus.
 *
 * \param dev_handle the handle to close
 */
API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
{
	struct libusb_context *ctx;
	unsigned char dummy = 1;
	ssize_t r;

	if (!dev_handle)
		return;
	usbi_dbg("");

	ctx = HANDLE_CTX(dev_handle);

	/* Similarly to libusb_open(), we want to interrupt all event handlers
	 * at this point. More importantly, we want to perform the actual close of
	 * the device while holding the event handling lock (preventing any other
	 * thread from doing event handling) because we will be removing a file
	 * descriptor from the polling loop. */

	/* record that we are messing with poll fds */
	pthread_mutex_lock(&ctx->pollfd_modify_lock);
	ctx->pollfd_modify++;
	pthread_mutex_unlock(&ctx->pollfd_modify_lock);

	/* write some data on control pipe to interrupt event handlers */
	r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
	if (r <= 0) {
		usbi_warn(ctx, "internal signalling write failed, closing anyway");
		do_close(ctx, dev_handle);
		pthread_mutex_lock(&ctx->pollfd_modify_lock);
		ctx->pollfd_modify--;
		pthread_mutex_unlock(&ctx->pollfd_modify_lock);
		return;
	}

	/* take event handling lock */
	libusb_lock_events(ctx);

	/* read the dummy data */
	r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
	if (r <= 0)
		usbi_warn(ctx, "internal signalling read failed, closing anyway");

	/* Close the device */
	do_close(ctx, dev_handle);

	/* we're done with modifying poll fds */
	pthread_mutex_lock(&ctx->pollfd_modify_lock);
	ctx->pollfd_modify--;
	pthread_mutex_unlock(&ctx->pollfd_modify_lock);

	/* Release event handling lock and wake up event waiters */
	libusb_unlock_events(ctx);
}

/** \ingroup dev
 * Get the underlying device for a handle. This function does not modify
 * the reference count of the returned device, so do not feel compelled to
 * unreference it when you are done.
 * \param dev_handle a device handle
 * \returns the underlying device
 */
API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
{
	return dev_handle->dev;
}

/** \ingroup dev
 * Determine the bConfigurationValue of the currently active configuration.
 *
 * You could formulate your own control request to obtain this information,
 * but this function has the advantage that it may be able to retrieve the
 * information from operating system caches (no I/O involved).
 *
 * If the OS does not cache this information, then this function will block
 * while a control transfer is submitted to retrieve the information.
 *
 * This function will return a value of 0 in the <tt>config</tt> output
 * parameter if the device is in unconfigured state.
 *
 * \param dev a device handle
 * \param config output location for the bConfigurationValue of the active
 * configuration (only valid for return code 0)
 * \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_get_configuration(libusb_device_handle *dev,
	int *config)
{
	int r = LIBUSB_ERROR_NOT_SUPPORTED;

	usbi_dbg("");
	if (usbi_backend->get_configuration)
		r = usbi_backend->get_configuration(dev, config);

	if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
		uint8_t tmp = 0;
		usbi_dbg("falling back to control message");
		r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
			LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
		if (r == 0) {
			usbi_err(HANDLE_CTX(dev), "zero bytes returned in ctrl transfer?");
			r = LIBUSB_ERROR_IO;
		} else if (r == 1) {
			r = 0;
			*config = tmp;
		} else {
			usbi_dbg("control failed, error %d", r);
		}
	}

	if (r == 0)
		usbi_dbg("active config %d", *config);

	return r;
}

/** \ingroup dev
 * Set the active configuration for a device.
 *
 * The operating system may or may not have already set an active
 * configuration on the device. It is up to your application to ensure the
 * correct configuration is selected before you attempt to claim interfaces
 * and perform other operations.
 *
 * If you call this function on a device already configured with the selected
 * configuration, then this function will act as a lightweight device reset:
 * it will issue a SET_CONFIGURATION request using the current configuration,
 * causing most USB-related device state to be reset (altsetting reset to zero,
 * endpoint halts cleared, toggles reset).
 *
 * You cannot change/reset configuration if your application has claimed
 * interfaces - you should free them with libusb_release_interface() first.
 * You cannot change/reset configuration if other applications or drivers have
 * claimed interfaces.
 *
 * A configuration value of -1 will put the device in unconfigured state.
 * The USB specifications state that a configuration value of 0 does this,
 * however buggy devices exist which actually have a configuration 0.
 *
 * You should always use this function rather than formulating your own
 * SET_CONFIGURATION control request. This is because the underlying operating
 * system needs to know when such changes happen.
 *
 * This is a blocking function.
 *
 * \param dev a device handle
 * \param configuration the bConfigurationValue of the configuration you
 * wish to activate, or -1 if you wish to put the device in unconfigured state
 * \returns 0 on success
 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
 * \returns another LIBUSB_ERROR code on other failure
 */
API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
	int configuration)
{
	usbi_dbg("configuration %d", configuration);
	return usbi_backend->set_configuration(dev, configuration);
}

/** \ingroup dev
 * Claim an interface on a given device handle. You must claim the interface
 * you wish to use before you can perform I/O on any of its endpoints.
 *
 * It is legal to attempt to claim an already-claimed interface, in which
 * case libusb just returns 0 without doing anything.
 *
 * Claiming of interfaces is a purely logical operation; it does not cause
 * any requests to be sent over the bus. Interface claiming is used to
 * instruct the underlying operating system that your application wishes
 * to take ownership of the interface.
 *
 * This is a non-blocking function.
 *
 * \param dev a device handle
 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
 * wish to claim
 * \returns 0 on success
 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
 * interface
 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
 * \returns a LIBUSB_ERROR code on other failure
 */
API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
	int interface_number)
{
	int r = 0;

	usbi_dbg("interface %d", interface_number);
	if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
		return LIBUSB_ERROR_INVALID_PARAM;

	pthread_mutex_lock(&dev->lock);
	if (dev->claimed_interfaces & (1 << interface_number))
		goto out;

	r = usbi_backend->claim_interface(dev, interface_number);
	if (r == 0)
		dev->claimed_interfaces |= 1 << interface_number;

out:
	pthread_mutex_unlock(&dev->lock);
	return r;
}

/** \ingroup dev
 * Release an interface previously claimed with libusb_claim_interface(). You
 * should release all claimed interfaces before closing a device handle.
 *