esp-idf/components/usb/usb_host.c

/*
 * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/*
Warning: The USB Host Library API is still a beta version and may be subject to change
*/

#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "sdkconfig.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "freertos/semphr.h"
#include "esp_err.h"
#include "esp_log.h"
#include "esp_heap_caps.h"
#include "hub.h"
#include "enum.h"
#include "usbh.h"
#include "hcd.h"
#include "esp_private/usb_phy.h"
#include "usb/usb_host.h"

static portMUX_TYPE host_lock = portMUX_INITIALIZER_UNLOCKED;

#define HOST_ENTER_CRITICAL_ISR()       portENTER_CRITICAL_ISR(&host_lock)
#define HOST_EXIT_CRITICAL_ISR()        portEXIT_CRITICAL_ISR(&host_lock)
#define HOST_ENTER_CRITICAL()           portENTER_CRITICAL(&host_lock)
#define HOST_EXIT_CRITICAL()            portEXIT_CRITICAL(&host_lock)
#define HOST_ENTER_CRITICAL_SAFE()      portENTER_CRITICAL_SAFE(&host_lock)
#define HOST_EXIT_CRITICAL_SAFE()       portEXIT_CRITICAL_SAFE(&host_lock)

#define HOST_CHECK(cond, ret_val) ({                                        \
            if (!(cond)) {                                                  \
                return (ret_val);                                           \
            }                                                               \
})
#define HOST_CHECK_FROM_CRIT(cond, ret_val) ({                              \
            if (!(cond)) {                                                  \
                HOST_EXIT_CRITICAL();                                       \
                return ret_val;                                             \
            }                                                               \
})

#define PROCESS_REQUEST_PENDING_FLAG_USBH       (1 << 0)
#define PROCESS_REQUEST_PENDING_FLAG_HUB        (1 << 1)
#define PROCESS_REQUEST_PENDING_FLAG_ENUM       (1 << 2)

#define SHORT_DESC_REQ_LEN                      8
#define CTRL_TRANSFER_MAX_DATA_LEN              CONFIG_USB_HOST_CONTROL_TRANSFER_MAX_SIZE

typedef struct ep_wrapper_s ep_wrapper_t;
typedef struct interface_s interface_t;
typedef struct client_s client_t;

struct ep_wrapper_s {
    // Dynamic members require a critical section
    struct {
        TAILQ_ENTRY(ep_wrapper_s) tailq_entry;
        union {
            struct {
                uint32_t pending: 1;
                uint32_t reserved31: 31;
            };
        } flags;
        uint32_t num_urb_inflight;
        usbh_ep_event_t last_event;
    } dynamic;
    // Constant members do no change after claiming the interface thus do not require a critical section
    struct {
        usbh_ep_handle_t ep_hdl;
        interface_t *intf_obj;
    } constant;
};

struct interface_s {
    // Dynamic members require a critical section
    struct {
        TAILQ_ENTRY(interface_s) tailq_entry;
    } mux_protected;
    // Constant members do no change after claiming the interface thus do not require a critical section
    struct {
        const usb_intf_desc_t *intf_desc;
        usb_device_handle_t dev_hdl;
        client_t *client_obj;
        ep_wrapper_t *endpoints[0];
    } constant;
};

struct client_s {
    // Dynamic members require a critical section
    struct {
        TAILQ_ENTRY(client_s) tailq_entry;
        TAILQ_HEAD(tailhead_pending_ep, ep_wrapper_s) pending_ep_tailq;
        TAILQ_HEAD(tailhead_idle_ep, ep_wrapper_s) idle_ep_tailq;
        TAILQ_HEAD(tailhead_done_ctrl_xfers, urb_s) done_ctrl_xfer_tailq;
        union {
            struct {
                uint32_t handling_events: 1;
                uint32_t taking_mux: 1;
                uint32_t reserved6: 6;
                uint32_t num_intf_claimed: 8;
                uint32_t reserved16: 16;
            };
            uint32_t val;
        } flags;
        uint32_t num_done_ctrl_xfer;
        uint32_t opened_dev_addr_map;
    } dynamic;
    // Mux protected members must be protected by host library the mux_lock when accessed
    struct {
        TAILQ_HEAD(tailhead_interfaces, interface_s) interface_tailq;
    } mux_protected;
    // Constant members do no change after registration thus do not require a critical section
    struct {
        SemaphoreHandle_t event_sem;
        usb_host_client_event_cb_t event_callback;
        void *callback_arg;
        QueueHandle_t event_msg_queue;
    } constant;
};

typedef struct {
    // Dynamic members require a critical section
    struct {
        // Access to these should be done in a critical section
        uint32_t process_pending_flags;
        uint32_t lib_event_flags;
        union {
            struct {
                uint32_t handling_events: 1;
                uint32_t reserved7: 7;
                uint32_t num_clients: 8;
                uint32_t reserved16: 16;
            };
            uint32_t val;
        } flags;
    } dynamic;
    // Mux protected members must be protected by host library the mux_lock when accessed
    struct {
        TAILQ_HEAD(tailhead_clients, client_s) client_tailq;  // List of all clients registered
    } mux_protected;
    // Constant members do no change after installation thus do not require a critical section
    struct {
        SemaphoreHandle_t event_sem;
        SemaphoreHandle_t mux_lock;
        usb_phy_handle_t phy_handle;    // Will be NULL if host library is installed with skip_phy_setup
        void *enum_client;              // Pointer to Enum driver (acting as a client). Used to reroute completed USBH control transfers
        void *hub_client;               // Pointer to External Hub driver (acting as a client). Used to reroute completed USBH control transfers. NULL, when External Hub Driver not available.
    } constant;
} host_lib_t;

static host_lib_t *p_host_lib_obj = NULL;

const char *USB_HOST_TAG = "USB HOST";

// ----------------------------------------------------- Helpers -------------------------------------------------------

static inline void _record_client_opened_device(client_t *client_obj, uint8_t dev_addr)
{
    assert(dev_addr != 0);
    client_obj->dynamic.opened_dev_addr_map |= (1 << (dev_addr - 1));
}

static inline void _clear_client_opened_device(client_t *client_obj, uint8_t dev_addr)
{
    assert(dev_addr != 0);
    client_obj->dynamic.opened_dev_addr_map &= ~(1 << (dev_addr - 1));
}

static inline bool _check_client_opened_device(client_t *client_obj, uint8_t dev_addr)
{
    bool ret;

    if (dev_addr != 0) {
        ret = client_obj->dynamic.opened_dev_addr_map & (1 << (dev_addr - 1));
    } else {
        ret = false;
    }

    return ret;
}

static bool _unblock_client(client_t *client_obj, bool in_isr)
{
    bool yield;

    HOST_EXIT_CRITICAL_SAFE();
    if (in_isr) {
        BaseType_t xTaskWoken = pdFALSE;
        xSemaphoreGiveFromISR(client_obj->constant.event_sem, &xTaskWoken);
        yield = (xTaskWoken == pdTRUE);
    } else {
        xSemaphoreGive(client_obj->constant.event_sem);
        yield = false;
    }
    HOST_ENTER_CRITICAL_SAFE();

    return yield;
}

static bool _unblock_lib(bool in_isr)
{
    bool yield;

    HOST_EXIT_CRITICAL_SAFE();
    if (in_isr) {
        BaseType_t xTaskWoken = pdFALSE;
        xSemaphoreGiveFromISR(p_host_lib_obj->constant.event_sem, &xTaskWoken);
        yield = (xTaskWoken == pdTRUE);
    } else {
        xSemaphoreGive(p_host_lib_obj->constant.event_sem);
        yield = false;
    }
    HOST_ENTER_CRITICAL_SAFE();

    return yield;
}

static inline bool _is_internal_client(void *client)
{
    if (p_host_lib_obj->constant.enum_client && (client == p_host_lib_obj->constant.enum_client)) {
        return true;
    }
#if ENABLE_USB_HUBS
    if (p_host_lib_obj->constant.hub_client && (client == p_host_lib_obj->constant.hub_client)) {
        return true;
    }
#endif // ENABLE_USB_HUBS
    return false;
}

static void send_event_msg_to_clients(const usb_host_client_event_msg_t *event_msg, bool send_to_all, uint8_t opened_dev_addr)
{
    // Lock client list
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    // Send event message to relevant or all clients
    client_t *client_obj;
    TAILQ_FOREACH(client_obj, &p_host_lib_obj->mux_protected.client_tailq, dynamic.tailq_entry) {
        if (!send_to_all) {
            // Check if client opened the device
            HOST_ENTER_CRITICAL();
            bool send = _check_client_opened_device(client_obj, opened_dev_addr);
            HOST_EXIT_CRITICAL();
            if (!send) {
                continue;
            }
        }
        // Send the event message
        if (xQueueSend(client_obj->constant.event_msg_queue, event_msg, 0) == pdTRUE) {
            HOST_ENTER_CRITICAL();
            _unblock_client(client_obj, false);
            HOST_EXIT_CRITICAL();
        } else {
            ESP_LOGE(USB_HOST_TAG, "Client event message queue full");
        }
    }
    // Unlock client list
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);
}

// ---------------------------------------------------- Callbacks ------------------------------------------------------

// ------------------- Library Related ---------------------

static bool proc_req_callback(usb_proc_req_source_t source, bool in_isr, void *arg)
{
    HOST_ENTER_CRITICAL_SAFE();
    // Store the processing request source
    switch (source) {
    case USB_PROC_REQ_SOURCE_USBH:
        p_host_lib_obj->dynamic.process_pending_flags |= PROCESS_REQUEST_PENDING_FLAG_USBH;
        break;
    case USB_PROC_REQ_SOURCE_HUB:
        p_host_lib_obj->dynamic.process_pending_flags |= PROCESS_REQUEST_PENDING_FLAG_HUB;
        break;
    case USB_PROC_REQ_SOURCE_ENUM:
        p_host_lib_obj->dynamic.process_pending_flags |= PROCESS_REQUEST_PENDING_FLAG_ENUM;
        break;
    }
    bool yield = _unblock_lib(in_isr);
    HOST_EXIT_CRITICAL_SAFE();

    return yield;
}

static void usbh_event_callback(usbh_event_data_t *event_data, void *arg)
{
    switch (event_data->event) {
    case USBH_EVENT_CTRL_XFER: {
        assert(event_data->ctrl_xfer_data.urb != NULL);
        assert(event_data->ctrl_xfer_data.urb->usb_host_client != NULL);
        // Redistribute completed control transfers to the clients that submitted them
        if (_is_internal_client(event_data->ctrl_xfer_data.urb->usb_host_client)) {
            // Simply call the transfer callback
            event_data->ctrl_xfer_data.urb->transfer.callback(&event_data->ctrl_xfer_data.urb->transfer);
        } else {
            client_t *client_obj = (client_t *)event_data->ctrl_xfer_data.urb->usb_host_client;
            HOST_ENTER_CRITICAL();
            TAILQ_INSERT_TAIL(&client_obj->dynamic.done_ctrl_xfer_tailq, event_data->ctrl_xfer_data.urb, tailq_entry);
            client_obj->dynamic.num_done_ctrl_xfer++;
            _unblock_client(client_obj, false);
            HOST_EXIT_CRITICAL();
        }
        break;
    }
    case USBH_EVENT_NEW_DEV: {
        // Prepare a NEW_DEV client event message, the send it to all clients
        usb_host_client_event_msg_t event_msg = {
            .event = USB_HOST_CLIENT_EVENT_NEW_DEV,
            .new_dev.address = event_data->new_dev_data.dev_addr,
        };
        send_event_msg_to_clients(&event_msg, true, 0);
#if ENABLE_USB_HUBS
        hub_notify_new_dev(event_data->new_dev_data.dev_addr);
#endif // ENABLE_USB_HUBS
        break;
    }
    case USBH_EVENT_DEV_GONE: {
#if ENABLE_USB_HUBS
        hub_notify_dev_gone(event_data->new_dev_data.dev_addr);
#endif // ENABLE_USB_HUBS
        // Prepare event msg, send only to clients that have opened the device
        usb_host_client_event_msg_t event_msg = {
            .event = USB_HOST_CLIENT_EVENT_DEV_GONE,
            .dev_gone.dev_hdl = event_data->dev_gone_data.dev_hdl,
        };
        send_event_msg_to_clients(&event_msg, false, event_data->dev_gone_data.dev_addr);
        break;
    }
    case USBH_EVENT_DEV_FREE: {
        // Let the Hub driver know that the device is free and its port can be recycled
        // Port could be absent, no need to verify
        hub_port_recycle(event_data->dev_free_data.parent_dev_hdl,
                         event_data->dev_free_data.port_num,
                         event_data->dev_free_data.dev_uid);
        break;
    }
    case USBH_EVENT_ALL_FREE: {
        // Notify the lib handler that all devices are free
        HOST_ENTER_CRITICAL();
        p_host_lib_obj->dynamic.lib_event_flags |= USB_HOST_LIB_EVENT_FLAGS_ALL_FREE;
        _unblock_lib(false);
        HOST_EXIT_CRITICAL();
        break;
    }
    default:
        abort();    // Should never occur
        break;
    }
}

static void hub_event_callback(hub_event_data_t *event_data, void *arg)
{
    switch (event_data->event) {
    case HUB_EVENT_CONNECTED:
        // Start enumeration process
        enum_start(event_data->connected.uid);
        break;
    case HUB_EVENT_RESET_COMPLETED:
        // Proceed enumeration process
        ESP_ERROR_CHECK(enum_proceed(event_data->reset_completed.uid));
        break;
    case HUB_EVENT_DISCONNECTED:
        // Cancel enumeration process
        enum_cancel(event_data->disconnected.uid);
        // We allow this to fail in case the device object was already freed
        usbh_devs_remove(event_data->disconnected.uid);
        break;
    default:
        abort();    // Should never occur
        break;
    }
}

static void enum_event_callback(enum_event_data_t *event_data, void *arg)
{
    enum_event_t event = event_data->event;

    switch (event) {
    case ENUM_EVENT_STARTED:
        // Enumeration process started
        break;
    case ENUM_EVENT_RESET_REQUIRED:
        hub_port_reset(event_data->reset_req.parent_dev_hdl, event_data->reset_req.parent_port_num);
        break;
    case ENUM_EVENT_COMPLETED:
        // Notify port that device completed enumeration
        hub_port_active(event_data->complete.parent_dev_hdl, event_data->complete.parent_port_num);
        // Propagate a new device event
        ESP_ERROR_CHECK(usbh_devs_new_dev_event(event_data->complete.dev_hdl));
        break;
    case ENUM_EVENT_CANCELED:
        // Enumeration canceled
        break;
    default:
        abort();    // Should never occur
        break;
    }
}

// ------------------- Client Related ----------------------

static bool endpoint_callback(usbh_ep_handle_t ep_hdl, usbh_ep_event_t ep_event, void *user_arg, bool in_isr)
{
    ep_wrapper_t *ep_wrap = (ep_wrapper_t *)user_arg;
    client_t *client_obj = (client_t *)ep_wrap->constant.intf_obj->constant.client_obj;

    HOST_ENTER_CRITICAL_SAFE();
    // Store the event to be handled later. Note that we allow overwriting of events because more severe will halt the pipe prevent any further events.
    ep_wrap->dynamic.last_event = ep_event;
    // Add the EP to the client's pending list if it's not in the list already
    if (!ep_wrap->dynamic.flags.pending) {
        ep_wrap->dynamic.flags.pending = 1;
        TAILQ_REMOVE(&client_obj->dynamic.idle_ep_tailq, ep_wrap, dynamic.tailq_entry);
        TAILQ_INSERT_TAIL(&client_obj->dynamic.pending_ep_tailq, ep_wrap, dynamic.tailq_entry);
    }
    bool yield = _unblock_client(client_obj, in_isr);
    HOST_EXIT_CRITICAL_SAFE();

    return yield;
}

static void get_config_desc_transfer_cb(usb_transfer_t *transfer)
{
    SemaphoreHandle_t transfer_done = (SemaphoreHandle_t)transfer->context;
    xSemaphoreGive(transfer_done);
}

// ------------------------------------------------ Library Functions --------------------------------------------------

// ----------------------- Public --------------------------

esp_err_t usb_host_install(const usb_host_config_t *config)
{
    HOST_CHECK(config != NULL, ESP_ERR_INVALID_ARG);
    HOST_ENTER_CRITICAL();
    HOST_CHECK_FROM_CRIT(p_host_lib_obj == NULL, ESP_ERR_INVALID_STATE);
    HOST_EXIT_CRITICAL();

    esp_err_t ret;
    host_lib_t *host_lib_obj = heap_caps_calloc(1, sizeof(host_lib_t), MALLOC_CAP_DEFAULT);
    SemaphoreHandle_t event_sem = xSemaphoreCreateBinary();
    SemaphoreHandle_t mux_lock = xSemaphoreCreateMutex();
    if (host_lib_obj == NULL || event_sem == NULL || mux_lock == NULL) {
        ret = ESP_ERR_NO_MEM;
        goto alloc_err;
    }
    // Initialize host library object
    TAILQ_INIT(&host_lib_obj->mux_protected.client_tailq);
    host_lib_obj->constant.event_sem = event_sem;
    host_lib_obj->constant.mux_lock = mux_lock;

    /*
    Install each layer of the Host stack (listed below) from the lowest layer to the highest
    - USB PHY
    - HCD
    - USBH
    - Enum
    - Hub
    */

    // Install USB PHY (if necessary). USB PHY driver will also enable the underlying Host Controller
    if (!config->skip_phy_setup) {
        // Host Library defaults to internal PHY
        usb_phy_config_t phy_config = {
            .controller = USB_PHY_CTRL_OTG,
            .target = USB_PHY_TARGET_INT,
            .otg_mode = USB_OTG_MODE_HOST,
            .otg_speed = USB_PHY_SPEED_UNDEFINED,   // In Host mode, the speed is determined by the connected device
            .ext_io_conf = NULL,
            .otg_io_conf = NULL,
        };
        ret = usb_new_phy(&phy_config, &host_lib_obj->constant.phy_handle);
        if (ret != ESP_OK) {
            goto phy_err;
        }
    }

    // Install HCD
    hcd_config_t hcd_config = {
        .intr_flags = config->intr_flags
    };
    ret = hcd_install(&hcd_config);
    if (ret != ESP_OK) {
        goto hcd_err;
    }

    // Install USBH
    usbh_config_t usbh_config = {
        .proc_req_cb = proc_req_callback,
        .proc_req_cb_arg = NULL,
        .event_cb = usbh_event_callback,
        .event_cb_arg = NULL,
    };
    ret = usbh_install(&usbh_config);
    if (ret != ESP_OK) {
        goto usbh_err;
    }

    // Install Enumeration driver
    enum_config_t enum_config = {
        .proc_req_cb = proc_req_callback,
        .proc_req_cb_arg = NULL,
        .enum_event_cb = enum_event_callback,
        .enum_event_cb_arg = NULL,
#if ENABLE_ENUM_FILTER_CALLBACK
        .enum_filter_cb = config->enum_filter_cb,
        .enum_filter_cb_arg = NULL,
#endif // ENABLE_ENUM_FILTER_CALLBACK
    };
    ret = enum_install(&enum_config, &host_lib_obj->constant.enum_client);
    if (ret != ESP_OK) {
        goto enum_err;
    }

    // Install Hub
    hub_config_t hub_config = {
        .proc_req_cb = proc_req_callback,
        .proc_req_cb_arg = NULL,
        .event_cb = hub_event_callback,
        .event_cb_arg = NULL,
    };
    ret = hub_install(&hub_config, &host_lib_obj->constant.hub_client);
    if (ret != ESP_OK) {
        goto hub_err;
    }

    // Assign host library object
    HOST_ENTER_CRITICAL();
    if (p_host_lib_obj != NULL) {
        HOST_EXIT_CRITICAL();
        ret = ESP_ERR_INVALID_STATE;
        goto assign_err;
    }
    p_host_lib_obj = host_lib_obj;
    HOST_EXIT_CRITICAL();

    // Start the root hub
    ESP_ERROR_CHECK(hub_root_start());
    ret = ESP_OK;
    return ret;

assign_err:
    ESP_ERROR_CHECK(hub_uninstall());
hub_err:
    ESP_ERROR_CHECK(enum_uninstall());
enum_err:
    ESP_ERROR_CHECK(usbh_uninstall());
usbh_err:
    ESP_ERROR_CHECK(hcd_uninstall());
hcd_err:
    if (host_lib_obj->constant.phy_handle) {
        ESP_ERROR_CHECK(usb_del_phy(host_lib_obj->constant.phy_handle));
    }
phy_err:
alloc_err:
    if (mux_lock) {
        vSemaphoreDelete(mux_lock);
    }
    if (event_sem) {
        vSemaphoreDelete(event_sem);
    }
    heap_caps_free(host_lib_obj);
    return ret;
}

esp_err_t usb_host_uninstall(void)
{
    // All devices must have been freed at this point
    HOST_ENTER_CRITICAL();
    HOST_CHECK_FROM_CRIT(p_host_lib_obj != NULL, ESP_ERR_INVALID_STATE);
    HOST_CHECK_FROM_CRIT(p_host_lib_obj->dynamic.process_pending_flags == 0 &&
                         p_host_lib_obj->dynamic.lib_event_flags == 0 &&
                         p_host_lib_obj->dynamic.flags.val == 0,
                         ESP_ERR_INVALID_STATE);
    HOST_EXIT_CRITICAL();

    // Stop the root hub
    ESP_ERROR_CHECK(hub_root_stop());

    // Unassign the host library object
    HOST_ENTER_CRITICAL();
    host_lib_t *host_lib_obj = p_host_lib_obj;
    p_host_lib_obj = NULL;
    HOST_EXIT_CRITICAL();

    /*
    Uninstall each layer of the Host stack (listed below) from the highest layer to the lowest
    - Hub
    - Enum
    - USBH
    - HCD
    - USB PHY
    */
    ESP_ERROR_CHECK(hub_uninstall());
    ESP_ERROR_CHECK(enum_uninstall());
    ESP_ERROR_CHECK(usbh_uninstall());
    ESP_ERROR_CHECK(hcd_uninstall());
    // If the USB PHY was setup, then delete it
    if (host_lib_obj->constant.phy_handle) {
        ESP_ERROR_CHECK(usb_del_phy(host_lib_obj->constant.phy_handle));
    }

    // Free memory objects
    vSemaphoreDelete(host_lib_obj->constant.mux_lock);
    vSemaphoreDelete(host_lib_obj->constant.event_sem);
    heap_caps_free(host_lib_obj);
    return ESP_OK;
}

esp_err_t usb_host_lib_handle_events(TickType_t timeout_ticks, uint32_t *event_flags_ret)
{
    // Check arguments and state
    HOST_CHECK(p_host_lib_obj != NULL, ESP_ERR_INVALID_STATE);

    esp_err_t ret = (timeout_ticks == 0) ? ESP_OK : ESP_ERR_TIMEOUT;    // We don't want to return ESP_ERR_TIMEOUT if we aren't blocking
    uint32_t event_flags;

    HOST_ENTER_CRITICAL();
    // Set handling_events flag. This prevents the host library from being uninstalled
    p_host_lib_obj->dynamic.flags.handling_events = 1;
    HOST_EXIT_CRITICAL();

    while (1) {
        // Loop until there are no more events
        if (xSemaphoreTake(p_host_lib_obj->constant.event_sem, timeout_ticks) == pdFALSE) {
            // Timed out waiting for semaphore or currently no events
            break;
        }

        // Read and clear process pending flags
        HOST_ENTER_CRITICAL();
        uint32_t process_pending_flags = p_host_lib_obj->dynamic.process_pending_flags;
        p_host_lib_obj->dynamic.process_pending_flags = 0;
        HOST_EXIT_CRITICAL();

        if (process_pending_flags & PROCESS_REQUEST_PENDING_FLAG_USBH) {
            ESP_ERROR_CHECK(usbh_process());
        }
        if (process_pending_flags & PROCESS_REQUEST_PENDING_FLAG_HUB) {
            ESP_ERROR_CHECK(hub_process());
        }
        if (process_pending_flags & PROCESS_REQUEST_PENDING_FLAG_ENUM) {
            ESP_ERROR_CHECK(enum_process());
        }

        ret = ESP_OK;
        // Set timeout_ticks to 0 so that we can check for events again without blocking
        timeout_ticks = 0;
    }

    HOST_ENTER_CRITICAL();
    p_host_lib_obj->dynamic.flags.handling_events = 0;
    // Read and clear any event flags
    event_flags = p_host_lib_obj->dynamic.lib_event_flags;
    p_host_lib_obj->dynamic.lib_event_flags = 0;
    HOST_EXIT_CRITICAL();

    if (event_flags_ret != NULL) {
        *event_flags_ret = event_flags;
    }
    return ret;
}

esp_err_t usb_host_lib_unblock(void)
{
    // All devices must have been freed at this point
    HOST_ENTER_CRITICAL();
    HOST_CHECK_FROM_CRIT(p_host_lib_obj != NULL, ESP_ERR_INVALID_STATE);
    _unblock_lib(false);
    HOST_EXIT_CRITICAL();
    return ESP_OK;
}

esp_err_t usb_host_lib_info(usb_host_lib_info_t *info_ret)
{
    HOST_CHECK(info_ret != NULL, ESP_ERR_INVALID_ARG);
    int num_devs_temp;
    int num_clients_temp;
    HOST_ENTER_CRITICAL();
    HOST_CHECK_FROM_CRIT(p_host_lib_obj != NULL, ESP_ERR_INVALID_STATE);
    num_clients_temp = p_host_lib_obj->dynamic.flags.num_clients;
    HOST_EXIT_CRITICAL();
    usbh_devs_num(&num_devs_temp);

    // Write back return values
    info_ret->num_devices = num_devs_temp;
    info_ret->num_clients = num_clients_temp;
    return ESP_OK;
}

// ------------------------------------------------ Client Functions ---------------------------------------------------

// ----------------------- Private -------------------------

static void _handle_pending_ep(client_t *client_obj)
{
    // Handle each EP on the pending list
    while (!TAILQ_EMPTY(&client_obj->dynamic.pending_ep_tailq)) {
        // Get the next pending EP.
        ep_wrapper_t *ep_wrap = TAILQ_FIRST(&client_obj->dynamic.pending_ep_tailq);
        TAILQ_REMOVE(&client_obj->dynamic.pending_ep_tailq, ep_wrap, dynamic.tailq_entry);
        TAILQ_INSERT_TAIL(&client_obj->dynamic.idle_ep_tailq, ep_wrap, dynamic.tailq_entry);
        ep_wrap->dynamic.flags.pending = 0;
        usbh_ep_event_t last_event = ep_wrap->dynamic.last_event;
        uint32_t num_urb_dequeued = 0;

        HOST_EXIT_CRITICAL();
        // Handle pipe event
        switch (last_event) {
        case USBH_EP_EVENT_ERROR_XFER:
        case USBH_EP_EVENT_ERROR_URB_NOT_AVAIL:
        case USBH_EP_EVENT_ERROR_OVERFLOW:
        case USBH_EP_EVENT_ERROR_STALL:
            // The endpoint is now stalled. Flush all pending URBs
            ESP_ERROR_CHECK(usbh_ep_command(ep_wrap->constant.ep_hdl, USBH_EP_CMD_FLUSH));
            // All URBs in this pipe are now retired waiting to be dequeued. Fall through to dequeue them
            __attribute__((fallthrough));
        case USBH_EP_EVENT_URB_DONE: {
            // Dequeue all URBs and run their transfer callback
            urb_t *urb;
            usbh_ep_dequeue_urb(ep_wrap->constant.ep_hdl, &urb);
            while (urb != NULL) {
                // Clear the transfer's in-flight flag to indicate the transfer is no longer in-flight
                urb->usb_host_inflight = false;
                urb->transfer.callback(&urb->transfer);
                num_urb_dequeued++;
                usbh_ep_dequeue_urb(ep_wrap->constant.ep_hdl, &urb);
            }
            break;
        }
        default:
            abort();    // Should never occur
            break;
        }
        HOST_ENTER_CRITICAL();

        // Update the endpoint's number of URB's in-flight
        assert(num_urb_dequeued <= ep_wrap->dynamic.num_urb_inflight);
        ep_wrap->dynamic.num_urb_inflight -= num_urb_dequeued;
    }
}

// ----------------------- Public --------------------------

esp_err_t usb_host_client_register(const usb_host_client_config_t *client_config, usb_host_client_handle_t *client_hdl_ret)
{
    HOST_CHECK(p_host_lib_obj, ESP_ERR_INVALID_STATE);
    HOST_CHECK(client_config != NULL && client_hdl_ret != NULL, ESP_ERR_INVALID_ARG);
    HOST_CHECK(client_config->max_num_event_msg > 0, ESP_ERR_INVALID_ARG);
    if (!client_config->is_synchronous) {
        // Asynchronous clients must provide a
        HOST_CHECK(client_config->async.client_event_callback != NULL, ESP_ERR_INVALID_ARG);
    }

    esp_err_t ret;
    // Create client object
    client_t *client_obj = heap_caps_calloc(1, sizeof(client_t), MALLOC_CAP_DEFAULT);
    SemaphoreHandle_t event_sem = xSemaphoreCreateBinary();
    QueueHandle_t event_msg_queue = xQueueCreate(client_config->max_num_event_msg, sizeof(usb_host_client_event_msg_t));
    if (client_obj == NULL || event_sem == NULL || event_msg_queue == NULL) {
        ret = ESP_ERR_NO_MEM;
        goto alloc_err;
    }
    // Initialize client object
    TAILQ_INIT(&client_obj->dynamic.pending_ep_tailq);
    TAILQ_INIT(&client_obj->dynamic.idle_ep_tailq);
    TAILQ_INIT(&client_obj->mux_protected.interface_tailq);
    TAILQ_INIT(&client_obj->dynamic.done_ctrl_xfer_tailq);
    client_obj->constant.event_sem = event_sem;
    client_obj->constant.event_callback = client_config->async.client_event_callback;
    client_obj->constant.callback_arg = client_config->async.callback_arg;
    client_obj->constant.event_msg_queue = event_msg_queue;

    // Add client to the host library's list of clients
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    HOST_ENTER_CRITICAL();
    p_host_lib_obj->dynamic.flags.num_clients++;
    HOST_EXIT_CRITICAL();
    TAILQ_INSERT_TAIL(&p_host_lib_obj->mux_protected.client_tailq, client_obj, dynamic.tailq_entry);
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);

    // Write back client handle
    *client_hdl_ret = (usb_host_client_handle_t)client_obj;
    ret = ESP_OK;
    return ret;

alloc_err:
    if (event_msg_queue) {
        vQueueDelete(event_msg_queue);
    }
    if (event_sem) {
        vSemaphoreDelete(event_sem);
    }
    heap_caps_free(client_obj);
    return ESP_OK;
}

esp_err_t usb_host_client_deregister(usb_host_client_handle_t client_hdl)
{
    HOST_CHECK(client_hdl != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;
    esp_err_t ret;

    // We take the mux_lock because we need to access the host library's client_tailq
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    HOST_ENTER_CRITICAL();
    // Check that client can currently deregistered
    bool can_deregister;
    if (!TAILQ_EMPTY(&client_obj->dynamic.pending_ep_tailq) ||
            !TAILQ_EMPTY(&client_obj->dynamic.idle_ep_tailq) ||
            !TAILQ_EMPTY(&client_obj->dynamic.done_ctrl_xfer_tailq) ||
            client_obj->dynamic.flags.handling_events ||
            client_obj->dynamic.flags.taking_mux ||
            client_obj->dynamic.flags.num_intf_claimed != 0 ||
            client_obj->dynamic.num_done_ctrl_xfer != 0 ||
            client_obj->dynamic.opened_dev_addr_map != 0) {
        can_deregister = false;
    } else {
        can_deregister = true;
    }
    HOST_EXIT_CRITICAL();
    if (!can_deregister) {
        ret = ESP_ERR_INVALID_STATE;
        goto exit;
    }

    // Remove client object from the library's list of clients
    TAILQ_REMOVE(&p_host_lib_obj->mux_protected.client_tailq, client_obj, dynamic.tailq_entry);
    HOST_ENTER_CRITICAL();
    p_host_lib_obj->dynamic.flags.num_clients--;
    if (p_host_lib_obj->dynamic.flags.num_clients == 0) {
        // This is the last client being deregistered. Notify the lib handler
        p_host_lib_obj->dynamic.lib_event_flags |= USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS;
        _unblock_lib(false);
    }
    HOST_EXIT_CRITICAL();
    // Free client object
    vQueueDelete(client_obj->constant.event_msg_queue);
    vSemaphoreDelete(client_obj->constant.event_sem);
    heap_caps_free(client_obj);
    ret = ESP_OK;
exit:
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);
    return ret;
}

esp_err_t usb_host_client_handle_events(usb_host_client_handle_t client_hdl, TickType_t timeout_ticks)
{
    // Check arguments and state
    HOST_CHECK(client_hdl != NULL, ESP_ERR_INVALID_ARG);
    HOST_CHECK(p_host_lib_obj != NULL, ESP_ERR_INVALID_STATE);

    esp_err_t ret = (timeout_ticks == 0) ? ESP_OK : ESP_ERR_TIMEOUT;    // We don't want to return ESP_ERR_TIMEOUT if we aren't blocking
    client_t *client_obj = (client_t *)client_hdl;

    HOST_ENTER_CRITICAL();
    // Set handling_events flag. This prevents the client from being deregistered
    client_obj->dynamic.flags.handling_events = 1;
    HOST_EXIT_CRITICAL();

    while (1) {
        // Loop until there are no more events
        if (xSemaphoreTake(client_obj->constant.event_sem, timeout_ticks) == pdFALSE) {
            // Timed out waiting for semaphore or currently no events
            break;
        }

        HOST_ENTER_CRITICAL();
        // Handle pending endpoints
        if (!TAILQ_EMPTY(&client_obj->dynamic.pending_ep_tailq)) {
            _handle_pending_ep(client_obj);
        }
        // Handle any done control transfers
        while (client_obj->dynamic.num_done_ctrl_xfer > 0) {
            urb_t *urb = TAILQ_FIRST(&client_obj->dynamic.done_ctrl_xfer_tailq);
            TAILQ_REMOVE(&client_obj->dynamic.done_ctrl_xfer_tailq, urb, tailq_entry);
            client_obj->dynamic.num_done_ctrl_xfer--;
            HOST_EXIT_CRITICAL();
            // Clear the transfer's in-flight flag to indicate the transfer is no longer in-flight
            urb->usb_host_inflight = false;
            // Call the transfer's callback
            urb->transfer.callback(&urb->transfer);
            HOST_ENTER_CRITICAL();
        }
        HOST_EXIT_CRITICAL();

        // Handle event messages
        while (uxQueueMessagesWaiting(client_obj->constant.event_msg_queue) > 0) {
            // Dequeue the event message and call the client event callback
            usb_host_client_event_msg_t event_msg;
            BaseType_t queue_ret = xQueueReceive(client_obj->constant.event_msg_queue, &event_msg, 0);
            assert(queue_ret == pdTRUE);
            client_obj->constant.event_callback(&event_msg, client_obj->constant.callback_arg);
        }

        ret = ESP_OK;
        // Set timeout_ticks to 0 so that we can check for events again without blocking
        timeout_ticks = 0;
    }

    HOST_ENTER_CRITICAL();
    client_obj->dynamic.flags.handling_events = 0;
    HOST_EXIT_CRITICAL();

    return ret;
}

esp_err_t usb_host_client_unblock(usb_host_client_handle_t client_hdl)
{
    HOST_CHECK(client_hdl != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;

    HOST_ENTER_CRITICAL();
    _unblock_client(client_obj, false);
    HOST_EXIT_CRITICAL();

    return ESP_OK;
}

// ------------------------------------------------- Device Handling ---------------------------------------------------

esp_err_t usb_host_device_open(usb_host_client_handle_t client_hdl, uint8_t dev_addr, usb_device_handle_t *dev_hdl_ret)
{
    HOST_CHECK(dev_addr > 0 && client_hdl != NULL && dev_hdl_ret != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;

    esp_err_t ret;
    usb_device_handle_t dev_hdl;
    ret = usbh_devs_open(dev_addr, &dev_hdl);
    if (ret != ESP_OK) {
        goto exit;
    }

    HOST_ENTER_CRITICAL();
    if (_check_client_opened_device(client_obj, dev_addr)) {
        // Client has already opened the device. Close it and return an error
        ret = ESP_ERR_INVALID_STATE;
        HOST_EXIT_CRITICAL();
        goto already_opened;
    }
    // Record in client object that we have opened the device of this address
    _record_client_opened_device(client_obj, dev_addr);
    HOST_EXIT_CRITICAL();

    *dev_hdl_ret = dev_hdl;
    ret = ESP_OK;
    return ret;

already_opened:
    ESP_ERROR_CHECK(usbh_dev_close(dev_hdl));
exit:
    return ret;
}

esp_err_t usb_host_device_close(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl)
{
    HOST_CHECK(dev_hdl != NULL && client_hdl != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;

    // We take the lock because we need to walk the interface list
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    esp_err_t ret;
    // Check that all interfaces claimed by this client do not belong to this device
    bool all_released = true;
    interface_t *intf_obj;
    TAILQ_FOREACH(intf_obj, &client_obj->mux_protected.interface_tailq, mux_protected.tailq_entry) {
        if (intf_obj->constant.dev_hdl == dev_hdl) {
            all_released = false;
            break;
        }
    }
    if (!all_released) {
        ret = ESP_ERR_INVALID_STATE;
        goto exit;
    }

    // Check that client actually opened the device in the first place
    HOST_ENTER_CRITICAL();
    uint8_t dev_addr;
    ESP_ERROR_CHECK(usbh_dev_get_addr(dev_hdl, &dev_addr));
    HOST_CHECK_FROM_CRIT(_check_client_opened_device(client_obj, dev_addr), ESP_ERR_NOT_FOUND);
    if (!_check_client_opened_device(client_obj, dev_addr)) {
        // Client never opened this device
        ret = ESP_ERR_INVALID_STATE;
        HOST_EXIT_CRITICAL();
        goto exit;
    }
    // Proceed to clear the record of the device form the client
    _clear_client_opened_device(client_obj, dev_addr);
    HOST_EXIT_CRITICAL();

    ESP_ERROR_CHECK(usbh_dev_close(dev_hdl));
    ret = ESP_OK;
exit:
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);
    return ret;
}

esp_err_t usb_host_device_free_all(void)
{
    HOST_ENTER_CRITICAL();
    HOST_CHECK_FROM_CRIT(p_host_lib_obj->dynamic.flags.num_clients == 0, ESP_ERR_INVALID_STATE);    // All clients must have been deregistered
    HOST_EXIT_CRITICAL();
    esp_err_t ret;
#if ENABLE_USB_HUBS
    hub_notify_all_free();
#endif // ENABLE_USB_HUBS
    ret = usbh_devs_mark_all_free();
    // If ESP_ERR_NOT_FINISHED is returned, caller must wait for USB_HOST_LIB_EVENT_FLAGS_ALL_FREE to confirm all devices are free
    return ret;
}

esp_err_t usb_host_device_addr_list_fill(int list_len, uint8_t *dev_addr_list, int *num_dev_ret)
{
    HOST_CHECK(dev_addr_list != NULL && num_dev_ret != NULL, ESP_ERR_INVALID_ARG);
    return usbh_devs_addr_list_fill(list_len, dev_addr_list, num_dev_ret);
}

// ------------------------------------------------- Device Requests ---------------------------------------------------

// ------------------- Cached Requests ---------------------

esp_err_t usb_host_device_info(usb_device_handle_t dev_hdl, usb_device_info_t *dev_info)
{
    HOST_CHECK(dev_hdl != NULL && dev_info != NULL, ESP_ERR_INVALID_ARG);
    return usbh_dev_get_info(dev_hdl, dev_info);
}

// ----------------------------------------------- Descriptor Requests -------------------------------------------------

// ----------------- Cached Descriptors --------------------

esp_err_t usb_host_get_device_descriptor(usb_device_handle_t dev_hdl, const usb_device_desc_t **device_desc)
{
    HOST_CHECK(dev_hdl != NULL && device_desc != NULL, ESP_ERR_INVALID_ARG);
    return usbh_dev_get_desc(dev_hdl, device_desc);
}

esp_err_t usb_host_get_active_config_descriptor(usb_device_handle_t dev_hdl, const usb_config_desc_t **config_desc)
{
    HOST_CHECK(dev_hdl != NULL && config_desc != NULL, ESP_ERR_INVALID_ARG);
    return usbh_dev_get_config_desc(dev_hdl, config_desc);
}

// ----------------- Descriptors Transfer Requests --------------------

static usb_transfer_status_t wait_for_transmission_done(usb_transfer_t *transfer)
{
    SemaphoreHandle_t transfer_done = (SemaphoreHandle_t)transfer->context;
    xSemaphoreTake(transfer_done, portMAX_DELAY);
    usb_transfer_status_t status = transfer->status;

    // EP0 halt->flush->clear is managed by USBH and lower layers
    return status;
}

static esp_err_t get_config_desc_transfer(usb_host_client_handle_t client_hdl, usb_transfer_t *ctrl_transfer, const int bConfigurationValue, const int num_bytes)
{
    const usb_device_desc_t *dev_desc;
    ESP_ERROR_CHECK(usbh_dev_get_desc(ctrl_transfer->device_handle, &dev_desc));

    usb_setup_packet_t *setup_pkt = (usb_setup_packet_t *)ctrl_transfer->data_buffer;
    USB_SETUP_PACKET_INIT_GET_CONFIG_DESC(setup_pkt, bConfigurationValue - 1, num_bytes);
    ctrl_transfer->num_bytes = sizeof(usb_setup_packet_t) + usb_round_up_to_mps(num_bytes, dev_desc->bMaxPacketSize0);

    // IN data stage should return exactly num_bytes (SHORT_DESC_REQ_LEN or wTotalLength) bytes
    const int expect_num_bytes = sizeof(usb_setup_packet_t) + num_bytes;

    // Submit control transfer
    esp_err_t ret = usb_host_transfer_submit_control(client_hdl, ctrl_transfer);
    if (ret != ESP_OK) {
        ESP_LOGE(USB_HOST_TAG, "Submit ctrl transfer failed");
        return ret;
    }

    // Wait for transfer to finish
    const usb_transfer_status_t status_short_desc = wait_for_transmission_done(ctrl_transfer);
    if (status_short_desc != USB_TRANSFER_STATUS_COMPLETED) {
        ESP_LOGE(USB_HOST_TAG, "Get config descriptor transfer status: %d", status_short_desc);
        ret = ESP_ERR_INVALID_STATE;
        return ret;
    }

    // Check IN transfer returned the expected correct number of bytes
    if ((expect_num_bytes != 0) && (ctrl_transfer->actual_num_bytes != expect_num_bytes)) {
        if (ctrl_transfer->actual_num_bytes > expect_num_bytes) {
            // The device returned more bytes than requested.
            // This violates the USB specs chapter 9.3.5, but we can continue
            ESP_LOGW(USB_HOST_TAG, "Incorrect number of bytes returned %d", ctrl_transfer->actual_num_bytes);
            return ESP_OK;
        } else {
            // The device returned less bytes than requested. We cannot continue.
            ESP_LOGE(USB_HOST_TAG, "Incorrect number of bytes returned %d", ctrl_transfer->actual_num_bytes);
            return ESP_ERR_INVALID_RESPONSE;
        }
    }
    return ESP_OK;
}

esp_err_t usb_host_get_config_desc(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bConfigurationValue, const usb_config_desc_t **config_desc_ret)
{
    esp_err_t ret = ESP_OK;
    HOST_CHECK(client_hdl != NULL && dev_hdl != NULL && config_desc_ret != NULL, ESP_ERR_INVALID_ARG);

    // Get number of configurations
    const usb_device_desc_t *dev_desc;
    ESP_ERROR_CHECK(usbh_dev_get_desc(dev_hdl, &dev_desc));

    HOST_CHECK(bConfigurationValue != 0, ESP_ERR_INVALID_ARG);
    HOST_CHECK(bConfigurationValue <= dev_desc->bNumConfigurations, ESP_ERR_NOT_SUPPORTED);

    // Initialize transfer
    usb_transfer_t *ctrl_transfer;
    if (usb_host_transfer_alloc(sizeof(usb_setup_packet_t) + CTRL_TRANSFER_MAX_DATA_LEN, 0, &ctrl_transfer)) {
        return ESP_ERR_NO_MEM;
    }

    SemaphoreHandle_t transfer_done = xSemaphoreCreateBinary();
    if (transfer_done == NULL) {
        ret = ESP_ERR_NO_MEM;
        goto exit;
    }

    ctrl_transfer->device_handle = dev_hdl;
    ctrl_transfer->bEndpointAddress = 0;
    ctrl_transfer->callback = get_config_desc_transfer_cb;
    ctrl_transfer->context = (void *)transfer_done;

    // Initiate control transfer for short config descriptor
    ret = get_config_desc_transfer(client_hdl, ctrl_transfer, bConfigurationValue, SHORT_DESC_REQ_LEN);
    if (ret != ESP_OK) {
        goto exit;
    }

    // Get length of full config descriptor
    const usb_config_desc_t *config_desc_short = (usb_config_desc_t *)(ctrl_transfer->data_buffer + sizeof(usb_setup_packet_t));

    // Initiate control transfer for full config descriptor
    ret = get_config_desc_transfer(client_hdl, ctrl_transfer, bConfigurationValue, config_desc_short->wTotalLength);
    if (ret != ESP_OK) {
        goto exit;
    }

    // Allocate memory to store the configuration descriptor
    const usb_config_desc_t *config_desc_full = (usb_config_desc_t *)(ctrl_transfer->data_buffer + sizeof(usb_setup_packet_t));
    usb_config_desc_t *config_desc = heap_caps_malloc(config_desc_full->wTotalLength, MALLOC_CAP_DEFAULT);
    if (config_desc == NULL) {
        ret = ESP_ERR_NO_MEM;
        goto exit;
    }

    // Copy the configuration descriptor
    memcpy(config_desc, config_desc_full, config_desc_full->wTotalLength);
    *config_desc_ret = config_desc;
    ret = ESP_OK;

exit:
    if (ctrl_transfer) {
        usb_host_transfer_free(ctrl_transfer);
    }
    if (transfer_done != NULL) {
        vSemaphoreDelete(transfer_done);
    }
    return ret;
}

esp_err_t usb_host_get_config_desc_free(const usb_config_desc_t *config_desc)
{
    HOST_CHECK(config_desc != NULL, ESP_ERR_INVALID_ARG);
    heap_caps_free((usb_config_desc_t*)config_desc);
    return ESP_OK;
}

// ----------------------------------------------- Interface Functions -------------------------------------------------

// ----------------------- Private -------------------------

static esp_err_t ep_wrapper_alloc(usb_device_handle_t dev_hdl, const usb_ep_desc_t *ep_desc, interface_t *intf_obj, ep_wrapper_t **ep_wrap_ret)
{
    ep_wrapper_t *ep_wrap = heap_caps_calloc(1, sizeof(ep_wrapper_t), MALLOC_CAP_DEFAULT);
    if (ep_wrap == NULL) {
        return ESP_ERR_NO_MEM;
    }
    esp_err_t ret;
    usbh_ep_handle_t ep_hdl;
    usbh_ep_config_t ep_config = {
        .bInterfaceNumber = intf_obj->constant.intf_desc->bInterfaceNumber,
        .bAlternateSetting = intf_obj->constant.intf_desc->bAlternateSetting,
        .bEndpointAddress = ep_desc->bEndpointAddress,
        .ep_cb = endpoint_callback,
        .ep_cb_arg = (void *)ep_wrap,
        .context = (void *)ep_wrap,
    };
    ret = usbh_ep_alloc(dev_hdl, &ep_config, &ep_hdl);
    if (ret != ESP_OK) {
        goto alloc_err;
    }
    // Initialize endpoint wrapper item
    ep_wrap->constant.ep_hdl = ep_hdl;
    ep_wrap->constant.intf_obj = intf_obj;
    // Write back result
    *ep_wrap_ret = ep_wrap;
    ret = ESP_OK;
    return ret;

alloc_err:
    heap_caps_free(ep_wrap);
    return ret;
}

static void ep_wrapper_free(usb_device_handle_t dev_hdl, ep_wrapper_t *ep_wrap)
{
    if (ep_wrap == NULL) {
        return;
    }
    // Free the underlying endpoint
    ESP_ERROR_CHECK(usbh_ep_free(ep_wrap->constant.ep_hdl));
    // Free the endpoint wrapper item
    heap_caps_free(ep_wrap);
}

static interface_t *interface_alloc(client_t *client_obj, usb_device_handle_t dev_hdl, const usb_intf_desc_t *intf_desc)
{
    interface_t *intf_obj = heap_caps_calloc(1, sizeof(interface_t) + (sizeof(ep_wrapper_t *) * intf_desc->bNumEndpoints), MALLOC_CAP_DEFAULT);
    if (intf_obj == NULL) {
        return NULL;
    }
    intf_obj->constant.intf_desc = intf_desc;
    intf_obj->constant.client_obj = client_obj;
    intf_obj->constant.dev_hdl = dev_hdl;
    return intf_obj;
}

static void interface_free(interface_t *intf_obj)
{
    if (intf_obj == NULL) {
        return;
    }
    for (int i = 0; i < intf_obj->constant.intf_desc->bNumEndpoints; i++) {
        assert(intf_obj->constant.endpoints[i] == NULL);
    }
    heap_caps_free(intf_obj);
}

static esp_err_t interface_claim(client_t *client_obj, usb_device_handle_t dev_hdl, const usb_config_desc_t *config_desc, uint8_t bInterfaceNumber, uint8_t bAlternateSetting, interface_t **intf_obj_ret)
{
    esp_err_t ret;
    // We need to walk to configuration descriptor to find the correct interface descriptor, and each of its constituent endpoint descriptors
    // Find the interface descriptor and allocate the interface object
    int offset_intf;
    const usb_intf_desc_t *intf_desc = usb_parse_interface_descriptor(config_desc, bInterfaceNumber, bAlternateSetting, &offset_intf);
    if (intf_desc == NULL) {
        ret = ESP_ERR_NOT_FOUND;
        goto exit;
    }
    // Allocate interface object
    interface_t *intf_obj = interface_alloc(client_obj, dev_hdl, intf_desc);
    if (intf_obj == NULL) {
        ret = ESP_ERR_NO_MEM;
        goto exit;
    }
    // Find each endpoint descriptor in the interface by index, and allocate those endpoints
    for (int i = 0; i < intf_desc->bNumEndpoints; i++) {
        int offset_ep = offset_intf;
        const usb_ep_desc_t *ep_desc = usb_parse_endpoint_descriptor_by_index(intf_desc, i, config_desc->wTotalLength, &offset_ep);
        if (ep_desc == NULL) {
            ret = ESP_ERR_NOT_FOUND;
            goto ep_alloc_err;
        }
        // Allocate the endpoint wrapper item
        ep_wrapper_t *ep_wrap;
        ret = ep_wrapper_alloc(dev_hdl, ep_desc, intf_obj, &ep_wrap);
        if (ret != ESP_OK) {
            goto ep_alloc_err;
        }
        // Fill the interface object with the allocated endpoints
        intf_obj->constant.endpoints[i] = ep_wrap;
    }
    // Add interface object to client (safe because we have already taken the mutex)
    TAILQ_INSERT_TAIL(&client_obj->mux_protected.interface_tailq, intf_obj, mux_protected.tailq_entry);
    // Add each endpoint wrapper item to the client's endpoint list
    HOST_ENTER_CRITICAL();
    for (int i = 0; i < intf_desc->bNumEndpoints; i++) {
        TAILQ_INSERT_TAIL(&client_obj->dynamic.idle_ep_tailq, intf_obj->constant.endpoints[i], dynamic.tailq_entry);
    }
    HOST_EXIT_CRITICAL();
    // Write back result
    *intf_obj_ret = intf_obj;
    ret = ESP_OK;
    return ret;

ep_alloc_err:
    for (int i = 0; i < intf_desc->bNumEndpoints; i++) {
        ep_wrapper_free(dev_hdl, intf_obj->constant.endpoints[i]);
        intf_obj->constant.endpoints[i] = NULL;
    }
    interface_free(intf_obj);
exit:
    return ret;
}

static esp_err_t interface_release(client_t *client_obj, usb_device_handle_t dev_hdl, uint8_t bInterfaceNumber)
{
    esp_err_t ret;
    // Find the interface object
    interface_t *intf_obj_iter;
    interface_t *intf_obj = NULL;
    TAILQ_FOREACH(intf_obj_iter, &client_obj->mux_protected.interface_tailq, mux_protected.tailq_entry) {
        if (intf_obj_iter->constant.dev_hdl == dev_hdl && intf_obj_iter->constant.intf_desc->bInterfaceNumber == bInterfaceNumber) {
            intf_obj = intf_obj_iter;
            break;
        }
    }
    if (intf_obj == NULL) {
        ret = ESP_ERR_NOT_FOUND;
        goto exit;
    }

    // Check that all endpoints in the interface are in a state to be freed
    // Todo: Check that each EP is halted before allowing them to be freed (IDF-7273)
    HOST_ENTER_CRITICAL();
    bool can_free = true;
    for (int i = 0; i < intf_obj->constant.intf_desc->bNumEndpoints; i++) {
        ep_wrapper_t *ep_wrap = intf_obj->constant.endpoints[i];
        // Endpoint must not be on the pending list and must not have in-flight URBs
        if (ep_wrap->dynamic.num_urb_inflight != 0 || ep_wrap->dynamic.flags.pending) {
            can_free = false;
            break;
        }
    }
    if (!can_free) {
        HOST_EXIT_CRITICAL();
        ret = ESP_ERR_INVALID_STATE;
        goto exit;
    }
    // Proceed to remove all endpoint wrapper items from the list
    for (int i = 0; i < intf_obj->constant.intf_desc->bNumEndpoints; i++) {
        TAILQ_REMOVE(&client_obj->dynamic.idle_ep_tailq, intf_obj->constant.endpoints[i], dynamic.tailq_entry);
    }
    HOST_EXIT_CRITICAL();

    // Remove the interface object from the list (safe because we have already taken the mutex)
    TAILQ_REMOVE(&client_obj->mux_protected.interface_tailq, intf_obj, mux_protected.tailq_entry);

    // Free each endpoint in the interface
    for (int i = 0; i < intf_obj->constant.intf_desc->bNumEndpoints; i++) {
        ep_wrapper_free(dev_hdl, intf_obj->constant.endpoints[i]);
        intf_obj->constant.endpoints[i] = NULL;
    }
    // Free the interface object itself
    interface_free(intf_obj);
    ret = ESP_OK;
exit:
    return ret;
}

// ----------------------- Public --------------------------

esp_err_t usb_host_interface_claim(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bInterfaceNumber, uint8_t bAlternateSetting)
{
    HOST_CHECK(client_hdl != NULL && dev_hdl != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;

    HOST_ENTER_CRITICAL();
    uint8_t dev_addr;
    ESP_ERROR_CHECK(usbh_dev_get_addr(dev_hdl, &dev_addr));
    // Check if client actually opened device
    HOST_CHECK_FROM_CRIT(_check_client_opened_device(client_obj, dev_addr), ESP_ERR_INVALID_STATE);
    client_obj->dynamic.flags.taking_mux = 1;
    HOST_EXIT_CRITICAL();

    // Take mux lock. This protects the client being released or other clients from claiming interfaces
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    esp_err_t ret;
    const usb_config_desc_t *config_desc;
    ESP_ERROR_CHECK(usbh_dev_get_config_desc(dev_hdl, &config_desc));
    interface_t *intf_obj;
    // Claim interface
    ret = interface_claim(client_obj, dev_hdl, config_desc, bInterfaceNumber, bAlternateSetting, &intf_obj);
    if (ret != ESP_OK) {
        goto exit;
    }
    ret = ESP_OK;
exit:
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);

    HOST_ENTER_CRITICAL();
    if (ret == ESP_OK) {
        client_obj->dynamic.flags.num_intf_claimed++;
    }
    client_obj->dynamic.flags.taking_mux = 0;
    HOST_EXIT_CRITICAL();
    return ret;
}

esp_err_t usb_host_interface_release(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bInterfaceNumber)
{
    HOST_CHECK(client_hdl != NULL && dev_hdl != NULL, ESP_ERR_INVALID_ARG);
    client_t *client_obj = (client_t *)client_hdl;

    HOST_ENTER_CRITICAL();
    uint8_t dev_addr;
    ESP_ERROR_CHECK(usbh_dev_get_addr(dev_hdl, &dev_addr));
    // Check if client actually opened device
    HOST_CHECK_FROM_CRIT(_check_client_opened_device(client_obj, dev_addr), ESP_ERR_INVALID_STATE);
    client_obj->dynamic.flags.taking_mux = 1;
    HOST_EXIT_CRITICAL();

    // Take mux lock. This protects the client being released or other clients from claiming interfaces
    xSemaphoreTake(p_host_lib_obj->constant.mux_lock, portMAX_DELAY);
    esp_err_t ret = interface_release(client_obj, dev_hdl, bInterfaceNumber);
    xSemaphoreGive(p_host_lib_obj->constant.mux_lock);

    HOST_ENTER_CRITICAL();
    if (ret == ESP_OK) {
        client_obj->dynamic.flags.num_intf_claimed--;
    }
    client_obj->dynamic.flags.taking_mux = 0;
    HOST_EXIT_CRITICAL();

    return ret;
}

esp_err_t usb_host_endpoint_halt(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)
{
    esp_err_t ret;
    usbh_ep_handle_t ep_hdl;

    ret = usbh_ep_get_handle(dev_hdl, bEndpointAddress, &ep_hdl);
    if (ret != ESP_OK) {
        goto exit;
    }
    ret = usbh_ep_command(ep_hdl, USBH_EP_CMD_HALT);

exit:
    return ret;
}

esp_err_t usb_host_endpoint_flush(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)
{
    esp_err_t ret;
    usbh_ep_handle_t ep_hdl;

    ret = usbh_ep_get_handle(dev_hdl, bEndpointAddress, &ep_hdl);
    if (ret != ESP_OK) {
        goto exit;
    }
    ret = usbh_ep_command(ep_hdl, USBH_EP_CMD_FLUSH);

exit:
    return ret;
}

esp_err_t usb_host_endpoint_clear(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)
{
    esp_err_t ret;
    usbh_ep_handle_t ep_hdl;

    ret = usbh_ep_get_handle(dev_hdl, bEndpointAddress, &ep_hdl);
    if (ret != ESP_OK) {
        goto exit;
    }
    ret = usbh_ep_command(ep_hdl, USBH_EP_CMD_CLEAR);

exit:
    return ret;
}

// ------------------------------------------------ Asynchronous I/O ---------------------------------------------------

// ----------------------- Public --------------------------

esp_err_t usb_host_transfer_alloc(size_t data_buffer_size, int num_isoc_packets, usb_transfer_t **transfer)
{
    urb_t *urb = urb_alloc(data_buffer_size, num_isoc_packets);
    if (urb == NULL) {
        return ESP_ERR_NO_MEM;
    }
    *transfer = &urb->transfer;
    return ESP_OK;
}

esp_err_t usb_host_transfer_free(usb_transfer_t *transfer)
{
    if (transfer == NULL) {
        return ESP_OK;
    }
    urb_t *urb = __containerof(transfer, urb_t, transfer);
    urb_free(urb);
    return ESP_OK;
}

esp_err_t usb_host_transfer_submit(usb_transfer_t *transfer)
{
    HOST_CHECK(transfer != NULL, ESP_ERR_INVALID_ARG);
    // Check that transfer and target endpoint are valid
    HOST_CHECK(transfer->device_handle != NULL, ESP_ERR_INVALID_ARG);   // Target device must be set
    HOST_CHECK((transfer->bEndpointAddress & USB_B_ENDPOINT_ADDRESS_EP_NUM_MASK) != 0, ESP_ERR_INVALID_ARG);

    usbh_ep_handle_t ep_hdl;
    ep_wrapper_t *ep_wrap = NULL;
    urb_t *urb_obj = __containerof(transfer, urb_t, transfer);
    esp_err_t ret;

    ret = usbh_ep_get_handle(transfer->device_handle, transfer->bEndpointAddress, &ep_hdl);
    if (ret != ESP_OK) {
        goto err;
    }
    ep_wrap = usbh_ep_get_context(ep_hdl);
    assert(ep_wrap != NULL);
    // Check that we are not submitting a transfer already in-flight
    HOST_CHECK(!urb_obj->usb_host_inflight, ESP_ERR_NOT_FINISHED);
    urb_obj->usb_host_inflight = true;
    HOST_ENTER_CRITICAL();
    ep_wrap->dynamic.num_urb_inflight++;
    HOST_EXIT_CRITICAL();

    ret = usbh_ep_enqueue_urb(ep_hdl, urb_obj);
    if (ret != ESP_OK) {
        goto submit_err;
    }
    return ret;

submit_err:
    HOST_ENTER_CRITICAL();
    ep_wrap->dynamic.num_urb_inflight--;
    HOST_EXIT_CRITICAL();
    urb_obj->usb_host_inflight = false;
err:
    return ret;
}

esp_err_t usb_host_transfer_submit_control(usb_host_client_handle_t client_hdl, usb_transfer_t *transfer)
{
    HOST_CHECK(client_hdl != NULL && transfer != NULL, ESP_ERR_INVALID_ARG);
    // Check that control transfer is valid
    HOST_CHECK(transfer->device_handle != NULL, ESP_ERR_INVALID_ARG);   // Target device must be set
    // Control transfers must be targeted at EP 0
    HOST_CHECK((transfer->bEndpointAddress & USB_B_ENDPOINT_ADDRESS_EP_NUM_MASK) == 0, ESP_ERR_INVALID_ARG);

    usb_device_handle_t dev_hdl = transfer->device_handle;
    urb_t *urb_obj = __containerof(transfer, urb_t, transfer);
    // Check that we are not submitting a transfer already in-flight
    HOST_CHECK(!urb_obj->usb_host_inflight, ESP_ERR_NOT_FINISHED);
    urb_obj->usb_host_inflight = true;
    // Save client handle into URB
    urb_obj->usb_host_client = (void *)client_hdl;

    esp_err_t ret;
    ret = usbh_dev_submit_ctrl_urb(dev_hdl, urb_obj);
    if (ret != ESP_OK) {
        urb_obj->usb_host_inflight = false;
    }
    return ret;
}