source: mainline/uspace/drv/bus/usb/usbhub/usbhub.c@ cd0cf81

/*
 * Copyright (c) 2010 Matus Dekanek
 * Copyright (c) 2011 Jan Vesely
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup drvusbhub
 * @{
 */
/** @file
 * @brief usb hub main functionality
 */

#include <ddf/driver.h>
#include <stdbool.h>
#include <errno.h>
#include <str_error.h>
#include <inttypes.h>
#include <stdio.h>

#include <usb/usb.h>
#include <usb/debug.h>
#include <usb/dev/pipes.h>
#include <usb/classes/classes.h>
#include <usb/descriptor.h>
#include <usb/dev/recognise.h>
#include <usb/dev/request.h>
#include <usb/classes/hub.h>
#include <usb/dev/poll.h>
#include <usbhc_iface.h>

#include "usbhub.h"
#include "status.h"

#define HUB_FNC_NAME "hub"

/** Hub status-change endpoint description.
 *
 * For more information see section 11.15.1 of USB 1.1 specification.
 */
const usb_endpoint_description_t hub_status_change_endpoint_description =
{
        .transfer_type = USB_TRANSFER_INTERRUPT,
        .direction = USB_DIRECTION_IN,
        .interface_class = USB_CLASS_HUB,
        .interface_subclass = 0,
        .interface_protocol = 0,
        .flags = 0
};

/** Standard get hub global status request */
static const usb_device_request_setup_packet_t get_hub_status_request = {
        .request_type = USB_HUB_REQ_TYPE_GET_HUB_STATUS,
        .request = USB_HUB_REQUEST_GET_STATUS,
        .index = 0,
        .value = 0,
        .length = sizeof(usb_hub_status_t),
};

static int usb_set_first_configuration(usb_device_t *usb_device);
static int usb_hub_process_hub_specific_info(usb_hub_dev_t *hub_dev);
static void usb_hub_over_current(const usb_hub_dev_t *hub_dev,
    usb_hub_status_t status);
static void usb_hub_global_interrupt(const usb_hub_dev_t *hub_dev);

static bool usb_hub_polling_error_callback(usb_device_t *dev, int err_code, void *arg)
{
        assert(dev);
        assert(arg);

        usb_log_error("Device %s polling error: %s", usb_device_get_name(dev), str_error(err_code));

        return true;
}

/**
 * Initialize hub device driver structure.
 *
 * Creates hub representation and fibril that periodically checks hub's status.
 * Hub representation is passed to the fibril.
 * @param usb_dev generic usb device information
 * @return error code
 */
int usb_hub_device_add(usb_device_t *usb_dev)
{
        assert(usb_dev);
        /* Create driver soft-state structure */
        usb_hub_dev_t *hub_dev =
            usb_device_data_alloc(usb_dev, sizeof(usb_hub_dev_t));
        if (hub_dev == NULL) {
                usb_log_error("Failed to create hub driver structure.");
                return ENOMEM;
        }
        hub_dev->usb_device = usb_dev;
        hub_dev->speed = usb_device_get_speed(usb_dev);

        fibril_mutex_initialize(&hub_dev->default_address_guard);
        fibril_condvar_initialize(&hub_dev->default_address_cv);

        /* Set hub's first configuration. (There should be only one) */
        int opResult = usb_set_first_configuration(usb_dev);
        if (opResult != EOK) {
                usb_log_error("Could not set hub configuration: %s",
                    str_error(opResult));
                return opResult;
        }

        /* Get port count and create attached_devices. */
        opResult = usb_hub_process_hub_specific_info(hub_dev);
        if (opResult != EOK) {
                usb_log_error("Could process hub specific info, %s",
                    str_error(opResult));
                return opResult;
        }

        /* Create hub control function. */
        usb_log_debug("Creating DDF function '" HUB_FNC_NAME "'.");
        hub_dev->hub_fun = usb_device_ddf_fun_create(hub_dev->usb_device,
            fun_exposed, HUB_FNC_NAME);
        if (hub_dev->hub_fun == NULL) {
                usb_log_error("Failed to create hub function.");
                return ENOMEM;
        }

        /* Bind hub control function. */
        opResult = ddf_fun_bind(hub_dev->hub_fun);
        if (opResult != EOK) {
                usb_log_error("Failed to bind hub function: %s.",
                   str_error(opResult));
                ddf_fun_destroy(hub_dev->hub_fun);
                return opResult;
        }

        /* Start hub operation. */
        usb_polling_t *polling = &hub_dev->polling;
        opResult = usb_polling_init(polling);
        if (opResult != EOK) {
                /* Function is already bound */
                ddf_fun_unbind(hub_dev->hub_fun);
                ddf_fun_destroy(hub_dev->hub_fun);
                usb_log_error("Failed to initialize polling fibril: %s.",
                    str_error(opResult));
                return opResult;
        }

        polling->device = hub_dev->usb_device;
        polling->ep_mapping = usb_device_get_mapped_ep_desc(hub_dev->usb_device,
            &hub_status_change_endpoint_description);
        polling->request_size = ((hub_dev->port_count + 1 + 7) / 8);
        polling->buffer = malloc(polling->request_size);
        polling->on_data = hub_port_changes_callback;
        polling->on_error = usb_hub_polling_error_callback;
        polling->arg = hub_dev;

        opResult = usb_polling_start(polling);
        if (opResult != EOK) {
                /* Polling is already initialized. */
                free(polling->buffer);
                usb_polling_fini(polling);
                ddf_fun_unbind(hub_dev->hub_fun);
                ddf_fun_destroy(hub_dev->hub_fun);
                usb_log_error("Failed to create polling fibril: %s.",
                    str_error(opResult));
                return opResult;
        }

        usb_log_info("Controlling %s-speed hub '%s' (%p: %zu ports).",
            usb_str_speed(hub_dev->speed),
            usb_device_get_name(hub_dev->usb_device), hub_dev,
            hub_dev->port_count);

        return EOK;
}

static int usb_hub_cleanup(usb_hub_dev_t *hub)
{
        free(hub->polling.buffer);
        usb_polling_fini(&hub->polling);

        for (size_t port = 0; port < hub->port_count; ++port) {
                usb_port_fini(&hub->ports[port].base);
        }
        free(hub->ports);

        const int ret = ddf_fun_unbind(hub->hub_fun);
        if (ret != EOK) {
                usb_log_error("(%p) Failed to unbind '%s' function: %s.",
                   hub, HUB_FNC_NAME, str_error(ret));
                return ret;
        }
        ddf_fun_destroy(hub->hub_fun);

        usb_log_info("(%p) USB hub driver stopped and cleaned.", hub);

        /* Device data (usb_hub_dev_t) will be freed by usbdev. */
        return EOK;
}

/**
 * Turn off power to all ports.
 *
 * @param usb_dev generic usb device information
 * @return error code
 */
int usb_hub_device_remove(usb_device_t *usb_dev)
{
        assert(usb_dev);
        usb_hub_dev_t *hub = usb_device_data_get(usb_dev);
        assert(hub);

        usb_log_info("(%p) USB hub removed, joining polling fibril.", hub);

        /* Join polling fibril (ignoring error code). */
        usb_polling_join(&hub->polling);
        usb_log_info("(%p) USB hub polling stopped, freeing memory.", hub);

        /* Destroy hub. */
        return usb_hub_cleanup(hub);
}

/**
 * Remove all attached devices
 * @param usb_dev generic usb device information
 * @return error code
 */
int usb_hub_device_gone(usb_device_t *usb_dev)
{
        assert(usb_dev);
        usb_hub_dev_t *hub = usb_device_data_get(usb_dev);
        assert(hub);

        usb_log_info("(%p) USB hub gone, joining polling fibril.", hub);

        /* Join polling fibril (ignoring error code). */
        usb_polling_join(&hub->polling);
        usb_log_info("(%p) USB hub polling stopped, freeing memory.", hub);

        /* Destroy hub. */
        return usb_hub_cleanup(hub);
}

/** Callback for polling hub for changes.
 *
 * @param dev Device where the change occured.
 * @param change_bitmap Bitmap of changed ports.
 * @param change_bitmap_size Size of the bitmap in bytes.
 * @param arg Custom argument, points to @c usb_hub_dev_t.
 * @return Whether to continue polling.
 */
bool hub_port_changes_callback(usb_device_t *dev,
    uint8_t *change_bitmap, size_t change_bitmap_size, void *arg)
{
        usb_hub_dev_t *hub = arg;
        assert(hub);

        /* It is an error condition if we didn't receive enough data */
        if (change_bitmap_size == 0) {
                return false;
        }

        /* Lowest bit indicates global change */
        const bool change = change_bitmap[0] & 1;
        if (change) {
                usb_hub_global_interrupt(hub);
        }

        /* N + 1 bit indicates change on port N */
        for (size_t port = 0; port < hub->port_count; ++port) {
                const size_t bit = port + 1;
                const bool change = (change_bitmap[bit / 8] >> (bit % 8)) & 1;
                if (change) {
                        usb_hub_port_process_interrupt(&hub->ports[port]);
                }
        }
        return true;
}

/**
 * Load hub-specific information into hub_dev structure and process if needed
 *
 * Read port count and initialize structures holding per port information.
 * If there are any non-removable devices, start initializing them.
 * This function is hub-specific and should be run only after the hub is
 * configured using usb_set_first_configuration function.
 * @param hub_dev hub representation
 * @return error code
 */
static int usb_hub_process_hub_specific_info(usb_hub_dev_t *hub_dev)
{
        assert(hub_dev);

        /* Get hub descriptor. */
        usb_log_debug("(%p): Retrieving descriptor.", hub_dev);
        usb_pipe_t *control_pipe =
            usb_device_get_default_pipe(hub_dev->usb_device);

        usb_descriptor_type_t desc_type = hub_dev->speed >= USB_SPEED_SUPER
                ? USB_DESCTYPE_SSPEED_HUB : USB_DESCTYPE_HUB;

        usb_hub_descriptor_header_t descriptor;
        size_t received_size;
        int opResult = usb_request_get_descriptor(control_pipe,
            USB_REQUEST_TYPE_CLASS, USB_REQUEST_RECIPIENT_DEVICE,
            desc_type, 0, 0, &descriptor,
            sizeof(usb_hub_descriptor_header_t), &received_size);
        if (opResult != EOK) {
                usb_log_error("(%p): Failed to receive hub descriptor: %s.",
                    hub_dev, str_error(opResult));
                return opResult;
        }

        usb_log_debug("(%p): Setting port count to %d.", hub_dev,
            descriptor.port_count);
        hub_dev->port_count = descriptor.port_count;
        hub_dev->control_pipe = control_pipe;

        usb_log_debug("(%p): Setting hub depth to %u.", hub_dev,
            usb_device_get_depth(hub_dev->usb_device));
        if ((opResult = usb_hub_set_depth(hub_dev))) {
                usb_log_error("(%p): Failed to set hub depth: %s.",
                    hub_dev, str_error(opResult));
                return opResult;
        }

        hub_dev->ports = calloc(hub_dev->port_count, sizeof(usb_hub_port_t));
        if (!hub_dev->ports) {
                return ENOMEM;
        }

        for (size_t port = 0; port < hub_dev->port_count; ++port) {
                usb_hub_port_init(&hub_dev->ports[port], hub_dev, port + 1);
        }

        hub_dev->power_switched =
            !(descriptor.characteristics & HUB_CHAR_NO_POWER_SWITCH_FLAG);
        hub_dev->per_port_power =
            descriptor.characteristics & HUB_CHAR_POWER_PER_PORT_FLAG;

        if (!hub_dev->power_switched) {
                usb_log_info("(%p): Power switching not supported, "
                    "ports always powered.", hub_dev);
                return EOK;
        }

        usb_log_info("(%p): Hub port power switching enabled (%s).", hub_dev,
            hub_dev->per_port_power ? "per port" : "ganged");

        for (unsigned int port = 0; port < hub_dev->port_count; ++port) {
                usb_log_debug("(%p): Powering port %u.", hub_dev, port + 1);
                const int ret = usb_hub_set_port_feature(hub_dev, port + 1, USB_HUB_FEATURE_PORT_POWER);

                if (ret != EOK) {
                        usb_log_error("(%p-%u): Cannot power on port: %s.",
                            hub_dev, hub_dev->ports[port].port_number,
                            str_error(ret));
                } else {
                        if (!hub_dev->per_port_power) {
                                usb_log_debug("(%p) Ganged power switching, port %u is probably already powered.", hub_dev, port + 1);
                        } else {
                                usb_log_warning("(%p): Failed to power port %u.", hub_dev, port + 1);
                        }
                }
        }
        return EOK;
}

/**
 * Set configuration of and USB device
 *
 * Check whether there is at least one configuration and sets the first one.
 * This function should be run prior to running any hub-specific action.
 * @param usb_device usb device representation
 * @return error code
 */
static int usb_set_first_configuration(usb_device_t *usb_device)
{
        assert(usb_device);
        /* Get number of possible configurations from device descriptor */
        const size_t configuration_count =
            usb_device_descriptors(usb_device)->device.configuration_count;
        usb_log_debug("Hub has %zu configurations.", configuration_count);

        if (configuration_count < 1) {
                usb_log_error("There are no configurations available");
                return EINVAL;
        }

        const size_t config_size =
            usb_device_descriptors(usb_device)->full_config_size;
        const usb_standard_configuration_descriptor_t *config_descriptor =
            usb_device_descriptors(usb_device)->full_config;

        if (config_size < sizeof(usb_standard_configuration_descriptor_t)) {
            usb_log_error("Configuration descriptor is not big enough"
                " to fit standard configuration descriptor.\n");
            return EOVERFLOW;
        }

        /* Set configuration. Use the configuration that was in
         * usb_device->descriptors.configuration i.e. The first one. */
        const int opResult = usb_request_set_configuration(
            usb_device_get_default_pipe(usb_device),
            config_descriptor->configuration_number);
        if (opResult != EOK) {
                usb_log_error("Failed to set hub configuration: %s.",
                    str_error(opResult));
        } else {
                usb_log_debug("\tUsed configuration %d",
                    config_descriptor->configuration_number);
        }
        return opResult;
}

/**
 * Process hub over current change
 *
 * This means either to power off the hub or power it on.
 * @param hub_dev hub instance
 * @param status hub status bitmask
 * @return error code
 */
static void usb_hub_over_current(const usb_hub_dev_t *hub_dev,
    usb_hub_status_t status)
{
        if (status & USB_HUB_STATUS_OVER_CURRENT) {
                /* Hub should remove power from all ports if it detects OC */
                usb_log_warning("(%p) Detected hub over-current condition, "
                    "all ports should be powered off.", hub_dev);
                return;
        }

        /* Ports are always powered. */
        if (!hub_dev->power_switched)
                return;

        /* Over-current condition is gone, it is safe to turn the ports on. */
        for (size_t port = 0; port < hub_dev->port_count; ++port) {
                const int ret = usb_hub_set_port_feature(hub_dev, port, USB_HUB_FEATURE_PORT_POWER);
                if (ret != EOK) {
                        usb_log_warning("(%p-%u): HUB OVER-CURRENT GONE: Cannot"
                            " power on port: %s\n", hub_dev,
                            hub_dev->ports[port].port_number, str_error(ret));
                } else {
                        if (!hub_dev->per_port_power)
                                return;
                }
        }
}

/**
 * Set feature on the real hub port.
 *
 * @param port Port structure.
 * @param feature Feature selector.
 */
int usb_hub_set_depth(const usb_hub_dev_t *hub)
{
        assert(hub);

        /* Slower hubs do not care about depth */
        if (hub->speed < USB_SPEED_SUPER)
                return EOK;

        const usb_device_request_setup_packet_t set_request = {
                .request_type = USB_HUB_REQ_TYPE_SET_HUB_DEPTH,
                .request = USB_HUB_REQUEST_SET_HUB_DEPTH,
                .value = uint16_host2usb(usb_device_get_depth(hub->usb_device) - 1),
                .index = 0,
                .length = 0,
        };
        return usb_pipe_control_write(hub->control_pipe, &set_request,
            sizeof(set_request), NULL, 0);
}

/**
 * Set feature on the real hub port.
 *
 * @param port Port structure.
 * @param feature Feature selector.
 */
int usb_hub_set_port_feature(const usb_hub_dev_t *hub, size_t port_number, usb_hub_class_feature_t feature)
{
        assert(hub);
        const usb_device_request_setup_packet_t clear_request = {
                .request_type = USB_HUB_REQ_TYPE_SET_PORT_FEATURE,
                .request = USB_DEVREQ_SET_FEATURE,
                .index = uint16_host2usb(port_number),
                .value = feature,
                .length = 0,
        };
        return usb_pipe_control_write(hub->control_pipe, &clear_request,
            sizeof(clear_request), NULL, 0);
}

/**
 * Clear feature on the real hub port.
 *
 * @param port Port structure.
 * @param feature Feature selector.
 */
int usb_hub_clear_port_feature(const usb_hub_dev_t *hub, size_t port_number, usb_hub_class_feature_t feature)
{
        assert(hub);
        const usb_device_request_setup_packet_t clear_request = {
                .request_type = USB_HUB_REQ_TYPE_CLEAR_PORT_FEATURE,
                .request = USB_DEVREQ_CLEAR_FEATURE,
                .value = feature,
                .index = uint16_host2usb(port_number),
                .length = 0,
        };
        return usb_pipe_control_write(hub->control_pipe,
            &clear_request, sizeof(clear_request), NULL, 0);
}

/**
 * Retrieve port status.
 *
 * @param[in] port Port structure
 * @param[out] status Where to store the port status.
 * @return Error code.
 */
int usb_hub_get_port_status(const usb_hub_dev_t *hub, size_t port_number, usb_port_status_t *status)
{
        assert(hub);
        assert(status);

        /* USB hub specific GET_PORT_STATUS request. See USB Spec 11.16.2.6
         * Generic GET_STATUS request cannot be used because of the difference
         * in status data size (2B vs. 4B)*/
        const usb_device_request_setup_packet_t request = {
                .request_type = USB_HUB_REQ_TYPE_GET_PORT_STATUS,
                .request = USB_HUB_REQUEST_GET_STATUS,
                .value = 0,
                .index = uint16_host2usb(port_number),
                .length = sizeof(usb_port_status_t),
        };
        size_t recv_size;

        uint32_t buffer;
        const int rc = usb_pipe_control_read(hub->control_pipe,
            &request, sizeof(usb_device_request_setup_packet_t),
            &buffer, sizeof(buffer), &recv_size);
        if (rc != EOK)
                return rc;

        if (recv_size != sizeof(*status))
                return ELIMIT;

        *status = uint32_usb2host(buffer);
        return EOK;
}

/**
 * Process hub interrupts.
 *
 * The change can be either in the over-current condition or local-power change.
 * @param hub_dev hub instance
 */
static void usb_hub_global_interrupt(const usb_hub_dev_t *hub_dev)
{
        assert(hub_dev);
        assert(hub_dev->usb_device);
        usb_log_debug("(%p): Global interrupt on th hub.",  hub_dev);
        usb_pipe_t *control_pipe =
            usb_device_get_default_pipe(hub_dev->usb_device);

        usb_hub_status_t status;
        size_t rcvd_size;
        /* NOTE: We can't use standard USB GET_STATUS request, because
         * hubs reply is 4byte instead of 2 */
        const int opResult = usb_pipe_control_read(control_pipe,
            &get_hub_status_request, sizeof(get_hub_status_request),
            &status, sizeof(usb_hub_status_t), &rcvd_size);
        if (opResult != EOK) {
                usb_log_error("(%p): Could not get hub status: %s.", hub_dev,
                    str_error(opResult));
                return;
        }
        if (rcvd_size != sizeof(usb_hub_status_t)) {
                usb_log_error("(%p): Received status has incorrect size: "
                    "%zu != %zu", hub_dev, rcvd_size, sizeof(usb_hub_status_t));
                return;
        }

        /* Handle status changes */
        if (status & USB_HUB_STATUS_C_OVER_CURRENT) {
                usb_hub_over_current(hub_dev, status);
                /* Ack change in hub OC flag */
                const int ret = usb_request_clear_feature(
                    control_pipe, USB_REQUEST_TYPE_CLASS,
                    USB_REQUEST_RECIPIENT_DEVICE,
                    USB_HUB_FEATURE_C_HUB_OVER_CURRENT, 0);
                if (ret != EOK) {
                        usb_log_error("(%p): Failed to clear hub over-current "
                            "change flag: %s.\n", hub_dev, str_error(opResult));
                }
        }

        if (status & USB_HUB_STATUS_C_LOCAL_POWER) {
                /* NOTE: Handling this is more complicated.
                 * If the transition is from bus power to local power, all
                 * is good and we may signal the parent hub that we don't
                 * need the power.
                 * If the transition is from local power to bus power
                 * the hub should turn off all the ports and devices need
                 * to be reinitialized taking into account the limited power
                 * that is now available.
                 * There is no support for power distribution in HelenOS,
                 * (or other OSes/hub devices that I've seen) so this is not
                 * implemented.
                 * Just ACK the change.
                 */
                const int ret = usb_request_clear_feature(
                    control_pipe, USB_REQUEST_TYPE_CLASS,
                    USB_REQUEST_RECIPIENT_DEVICE,
                    USB_HUB_FEATURE_C_HUB_LOCAL_POWER, 0);
                if (opResult != EOK) {
                        usb_log_error("(%p): Failed to clear hub power change "
                            "flag: %s.\n", hub_dev, str_error(ret));
                }
        }
}

static FIBRIL_CONDVAR_INITIALIZE(global_hub_default_address_cv);

/**
 * Reserve a default address for a port across all other devices connected to
 * the bus. We aggregate requests for ports to minimize delays between
 * connecting multiple devices from one hub - which happens e.g. when the hub
 * is connected with already attached devices.
 */
int usb_hub_reserve_default_address(usb_hub_dev_t *hub, async_exch_t *exch, usb_port_t *port)
{
        assert(hub);
        assert(exch);
        assert(port);
        assert(fibril_mutex_is_locked(&port->guard));

        fibril_mutex_lock(&hub->default_address_guard);
        if (hub->default_address_requests++ == 0) {
                /* We're the first to request the address, we can just do it */
                fibril_mutex_unlock(&hub->default_address_guard);
                int err;
                while ((err = usbhc_reserve_default_address(exch)) == EAGAIN) {
                        // We ignore the return value here, as we cannot give up now.
                        usb_port_condvar_wait_timeout(port, &global_hub_default_address_cv, 500000);
                }
                return err;
        } else {
                /* Drop the port guard, we're going to wait */
                fibril_mutex_unlock(&port->guard);

                /* Wait for a signal */
                fibril_condvar_wait(&hub->default_address_cv, &hub->default_address_guard);

                /* Remember ABBA, first drop the hub guard */
                fibril_mutex_unlock(&hub->default_address_guard);
                fibril_mutex_lock(&port->guard);
                return EOK;
        }
}

/**
 * Release the default address from a port.
 */
int usb_hub_release_default_address(usb_hub_dev_t *hub, async_exch_t *exch)
{
        int ret = EOK;

        fibril_mutex_lock(&hub->default_address_guard);
        if (--hub->default_address_requests == 0) {
                // We must do it in critical section to prevent other fibril
                // from requesting the address before we release
                ret = usbhc_release_default_address(exch);
                // This is optimistic optimization - it may wake one hub from polling sleep
                fibril_condvar_signal(&global_hub_default_address_cv);
        } else {
                fibril_condvar_signal(&hub->default_address_cv);
        }
        fibril_mutex_unlock(&hub->default_address_guard);

        return ret;
}

/**
 * @}
 */