source: mainline/uspace/drv/bus/usb/xhci/commands.c@ ef1a3a8

/*
 * Copyright (c) 2017 Jaroslav Jindrak
 * 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 drvusbxhci
 * @{
 */
/** @file
 * @brief Command sending functions.
 */

#include <errno.h>
#include <str_error.h>
#include <usb/debug.h>
#include <usb/host/utils/malloc32.h>
#include "commands.h"
#include "debug.h"
#include "hc.h"
#include "hw_struct/context.h"
#include "hw_struct/trb.h"

#define TRB_SET_TCS(trb, tcs)   (trb).control |= host2xhci(32, ((tcs &0x1) << 9))
#define TRB_SET_TYPE(trb, type) (trb).control |= host2xhci(32, (type) << 10)
#define TRB_SET_DC(trb, dc)     (trb).control |= host2xhci(32, (dc) << 9)
#define TRB_SET_EP(trb, ep)     (trb).control |= host2xhci(32, ((ep) & 0x5) << 16)
#define TRB_SET_STREAM(trb, st) (trb).control |= host2xhci(32, ((st) & 0xFFFF) << 16)
#define TRB_SET_SUSP(trb, susp) (trb).control |= host2xhci(32, ((susp) & 0x1) << 23)
#define TRB_SET_SLOT(trb, slot) (trb).control |= host2xhci(32, (slot) << 24)
#define TRB_SET_DEV_SPEED(trb, speed)   (trb).control |= host2xhci(32, (speed & 0xF) << 16)

/**
 * TODO: Not sure about SCT and DCS (see section 6.4.3.9).
 */
#define TRB_SET_DEQUEUE_PTR(trb, dptr) (trb).parameter |= host2xhci(64, (dptr))
#define TRB_SET_ICTX(trb, phys) (trb).parameter |= host2xhci(64, phys_addr & (~0xF))

#define TRB_GET_CODE(trb) XHCI_DWORD_EXTRACT((trb).status, 31, 24)
#define TRB_GET_SLOT(trb) XHCI_DWORD_EXTRACT((trb).control, 31, 24)
#define TRB_GET_PHYS(trb) (XHCI_QWORD_EXTRACT((trb).parameter, 63, 4) << 4)

/* Control functions */

int xhci_init_commands(xhci_hc_t *hc)
{
        assert(hc);

        list_initialize(&hc->commands);

        fibril_mutex_initialize(&hc->commands_mtx);

        return EOK;
}

void xhci_fini_commands(xhci_hc_t *hc)
{
        // Note: Untested.
        assert(hc);
}

void xhci_cmd_init(xhci_cmd_t *cmd, xhci_cmd_type_t type)
{
        memset(cmd, 0, sizeof(*cmd));

        link_initialize(&cmd->_header.link);

        fibril_mutex_initialize(&cmd->_header.completed_mtx);
        fibril_condvar_initialize(&cmd->_header.completed_cv);

        cmd->_header.cmd = type;
        cmd->_header.timeout = XHCI_DEFAULT_TIMEOUT;
}

void xhci_cmd_fini(xhci_cmd_t *cmd)
{
        list_remove(&cmd->_header.link);

        if (cmd->input_ctx) {
                free32(cmd->input_ctx);
        };

        if (cmd->bandwidth_ctx) {
                free32(cmd->bandwidth_ctx);
        }

        if (cmd->_header.async) {
                free(cmd);
        }
}

static inline xhci_cmd_t *get_command(xhci_hc_t *hc, uint64_t phys)
{
        fibril_mutex_lock(&hc->commands_mtx);

        link_t *cmd_link = list_first(&hc->commands);

        while (cmd_link != NULL) {
                xhci_cmd_t *cmd = list_get_instance(cmd_link, xhci_cmd_t, _header.link);

                if (cmd->_header.trb_phys == phys)
                        break;

                cmd_link = list_next(cmd_link, &hc->commands);
        }

        if (cmd_link != NULL) {
                list_remove(cmd_link);
                fibril_mutex_unlock(&hc->commands_mtx);

                return list_get_instance(cmd_link, xhci_cmd_t, _header.link);
        }

        fibril_mutex_unlock(&hc->commands_mtx);
        return NULL;
}

static inline int enqueue_command(xhci_hc_t *hc, xhci_cmd_t *cmd, unsigned doorbell, unsigned target)
{
        assert(hc);
        assert(cmd);

        fibril_mutex_lock(&hc->commands_mtx);
        list_append(&cmd->_header.link, &hc->commands);
        fibril_mutex_unlock(&hc->commands_mtx);

        xhci_trb_ring_enqueue(&hc->command_ring, &cmd->_header.trb, &cmd->_header.trb_phys);
        hc_ring_doorbell(hc, doorbell, target);

        usb_log_debug2("HC(%p): Sent command:", hc);
        xhci_dump_trb(&cmd->_header.trb);

        return EOK;
}

void xhci_stop_command_ring(xhci_hc_t *hc)
{
        assert(hc);

        XHCI_REG_SET(hc->op_regs, XHCI_OP_CS, 1);

        /**
         * Note: There is a bug in qemu that checks CS only when CRCR_HI
         *       is written, this (and the read/write in abort) ensures
         *       the command rings stops.
         */
        XHCI_REG_WR(hc->op_regs, XHCI_OP_CRCR_HI, XHCI_REG_RD(hc->op_regs, XHCI_OP_CRCR_HI));
}

void xhci_abort_command_ring(xhci_hc_t *hc)
{
        assert(hc);

        XHCI_REG_WR(hc->op_regs, XHCI_OP_CA, 1);
        XHCI_REG_WR(hc->op_regs, XHCI_OP_CRCR_HI, XHCI_REG_RD(hc->op_regs, XHCI_OP_CRCR_HI));
}

void xhci_start_command_ring(xhci_hc_t *hc)
{
        assert(hc);

        XHCI_REG_WR(hc->op_regs, XHCI_OP_CRR, 1);
        hc_ring_doorbell(hc, 0, 0);
}

static const char *trb_codes [] = {
#define TRBC(t) [XHCI_TRBC_##t] = #t
        TRBC(INVALID),
        TRBC(SUCCESS),
        TRBC(DATA_BUFFER_ERROR),
        TRBC(BABBLE_DETECTED_ERROR),
        TRBC(USB_TRANSACTION_ERROR),
        TRBC(TRB_ERROR),
        TRBC(STALL_ERROR),
        TRBC(RESOURCE_ERROR),
        TRBC(BANDWIDTH_ERROR),
        TRBC(NO_SLOTS_ERROR),
        TRBC(INVALID_STREAM_ERROR),
        TRBC(SLOT_NOT_ENABLED_ERROR),
        TRBC(EP_NOT_ENABLED_ERROR),
        TRBC(SHORT_PACKET),
        TRBC(RING_UNDERRUN),
        TRBC(RING_OVERRUN),
        TRBC(VF_EVENT_RING_FULL),
        TRBC(PARAMETER_ERROR),
        TRBC(BANDWIDTH_OVERRUN_ERROR),
        TRBC(CONTEXT_STATE_ERROR),
        TRBC(NO_PING_RESPONSE_ERROR),
        TRBC(EVENT_RING_FULL_ERROR),
        TRBC(INCOMPATIBLE_DEVICE_ERROR),
        TRBC(MISSED_SERVICE_ERROR),
        TRBC(COMMAND_RING_STOPPED),
        TRBC(COMMAND_ABORTED),
        TRBC(STOPPED),
        TRBC(STOPPED_LENGTH_INVALID),
        TRBC(STOPPED_SHORT_PACKET),
        TRBC(MAX_EXIT_LATENCY_TOO_LARGE_ERROR),
        [30] = "<reserved>",
        TRBC(ISOCH_BUFFER_OVERRUN),
        TRBC(EVENT_LOST_ERROR),
        TRBC(UNDEFINED_ERROR),
        TRBC(INVALID_STREAM_ID_ERROR),
        TRBC(SECONDARY_BANDWIDTH_ERROR),
        TRBC(SPLIT_TRANSACTION_ERROR),
        [XHCI_TRBC_MAX] = NULL
#undef TRBC
};

static void report_error(int code)
{
        if (code < XHCI_TRBC_MAX && trb_codes[code] != NULL)
                usb_log_error("Command resulted in error: %s.", trb_codes[code]);
        else
                usb_log_error("Command resulted in reserved or vendor specific error.");
}

int xhci_handle_command_completion(xhci_hc_t *hc, xhci_trb_t *trb)
{
        // TODO: Update dequeue ptrs.
        assert(hc);
        assert(trb);

        usb_log_debug2("HC(%p) Command completed.", hc);

        int code;
        uint64_t phys;
        xhci_cmd_t *command;

        code = TRB_GET_CODE(*trb);
        phys = TRB_GET_PHYS(*trb);;
        command = get_command(hc, phys);
        if (command == NULL) {
                // TODO: STOP & ABORT may not have command structs in the list!
                usb_log_warning("No command struct for this completion event found.");

                if (code != XHCI_TRBC_SUCCESS)
                        report_error(code);

                return EOK;
        }

        /* Semantics of NO_OP_CMD is that success is marked as a TRB error. */
        if (command->_header.cmd == XHCI_CMD_NO_OP && code == XHCI_TRBC_TRB_ERROR)
                code = XHCI_TRBC_SUCCESS;

        command->status = code;
        command->slot_id = TRB_GET_SLOT(*trb);

        usb_log_debug2("Completed command trb: %s", xhci_trb_str_type(TRB_TYPE(command->_header.trb)));

        if (code != XHCI_TRBC_SUCCESS) {
                report_error(code);
                xhci_dump_trb(&command->_header.trb);
        }

        switch (TRB_TYPE(command->_header.trb)) {
        case XHCI_TRB_TYPE_NO_OP_CMD:
                break;
        case XHCI_TRB_TYPE_ENABLE_SLOT_CMD:
                break;
        case XHCI_TRB_TYPE_DISABLE_SLOT_CMD:
                break;
        case XHCI_TRB_TYPE_ADDRESS_DEVICE_CMD:
                break;
        case XHCI_TRB_TYPE_CONFIGURE_ENDPOINT_CMD:
                break;
        case XHCI_TRB_TYPE_EVALUATE_CONTEXT_CMD:
                break;
        case XHCI_TRB_TYPE_RESET_ENDPOINT_CMD:
                break;
        case XHCI_TRB_TYPE_STOP_ENDPOINT_CMD:
                // Note: If the endpoint was in the middle of a transfer, then the xHC
                //       will add a Transfer TRB before the Event TRB, research that and
                //       handle it appropriately!
                break;
        case XHCI_TRB_TYPE_RESET_DEVICE_CMD:
                break;
        default:
                usb_log_debug2("Unsupported command trb: %s", xhci_trb_str_type(TRB_TYPE(command->_header.trb)));

                command->_header.completed = true;
                return ENAK;
        }

        fibril_mutex_lock(&command->_header.completed_mtx);
        command->_header.completed = true;
        fibril_condvar_broadcast(&command->_header.completed_cv);
        fibril_mutex_unlock(&command->_header.completed_mtx);

        if (command->_header.async) {
                /* Free the command and other DS upon completion. */
                xhci_cmd_fini(command);
        }

        return EOK;
}

/* Command-issuing functions */

static int no_op_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_NO_OP_CMD);

        return enqueue_command(hc, cmd, 0, 0);
}

static int enable_slot_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_ENABLE_SLOT_CMD);
        cmd->_header.trb.control |= host2xhci(32, XHCI_REG_RD(hc->xecp, XHCI_EC_SP_SLOT_TYPE) << 16);

        return enqueue_command(hc, cmd, 0, 0);
}

static int disable_slot_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_DISABLE_SLOT_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int address_device_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);
        assert(cmd->input_ctx);

        /**
         * TODO: Requirements for this command:
         *           dcbaa[slot_id] is properly sized and initialized
         *           ictx has valids slot context and endpoint 0, all
         *           other should be ignored at this point (see section 4.6.5).
         */

        xhci_trb_clean(&cmd->_header.trb);

        uint64_t phys_addr = (uint64_t) addr_to_phys(cmd->input_ctx);
        TRB_SET_ICTX(cmd->_header.trb, phys_addr);

        /**
         * Note: According to section 6.4.3.4, we can set the 9th bit
         *       of the control field of the trb (BSR) to 1 and then the xHC
         *       will not issue the SET_ADDRESS request to the USB device.
         *       This can be used to provide compatibility with legacy USB devices
         *       that require their device descriptor to be read before such request.
         */
        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_ADDRESS_DEVICE_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int configure_endpoint_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        if (!cmd->deconfigure) {
                /* If the DC flag is on, input context is not evaluated. */
                assert(cmd->input_ctx);

                uint64_t phys_addr = (uint64_t) addr_to_phys(cmd->input_ctx);
                TRB_SET_ICTX(cmd->_header.trb, phys_addr);
        }

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_CONFIGURE_ENDPOINT_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);
        TRB_SET_DC(cmd->_header.trb, cmd->deconfigure);

        return enqueue_command(hc, cmd, 0, 0);
}

static int evaluate_context_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);
        assert(cmd->input_ctx);

        /**
         * Note: All Drop Context flags of the input context shall be 0,
         *       all Add Context flags shall be initialize to indicate IDs
         *       of the contexts affected by the command.
         *       Refer to sections 6.2.2.3 and 6.3.3.3 for further info.
         */
        xhci_trb_clean(&cmd->_header.trb);

        uint64_t phys_addr = (uint64_t) addr_to_phys(cmd->input_ctx);
        TRB_SET_ICTX(cmd->_header.trb, phys_addr);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_EVALUATE_CONTEXT_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int reset_endpoint_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        /**
         * Note: TCS can have values 0 or 1. If it is set to 0, see sectuon 4.5.8 for
         *       information about this flag.
         */
        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_RESET_ENDPOINT_CMD);
        TRB_SET_TCS(cmd->_header.trb, cmd->tcs);
        TRB_SET_EP(cmd->_header.trb, cmd->endpoint_id);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int stop_endpoint_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_STOP_ENDPOINT_CMD);
        TRB_SET_EP(cmd->_header.trb, cmd->endpoint_id);
        TRB_SET_SUSP(cmd->_header.trb, cmd->susp);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int set_tr_dequeue_pointer_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_SET_TR_DEQUEUE_POINTER_CMD);
        TRB_SET_EP(cmd->_header.trb, cmd->endpoint_id);
        TRB_SET_STREAM(cmd->_header.trb, cmd->stream_id);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);
        TRB_SET_DEQUEUE_PTR(cmd->_header.trb, cmd->dequeue_ptr);

        /**
         * TODO: Set DCS (see section 4.6.10).
         */

        return enqueue_command(hc, cmd, 0, 0);
}

static int reset_device_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_RESET_DEVICE_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);

        return enqueue_command(hc, cmd, 0, 0);
}

static int get_port_bandwidth_cmd(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        xhci_trb_clean(&cmd->_header.trb);

        uint64_t phys_addr = (uint64_t) addr_to_phys(cmd->bandwidth_ctx);
        TRB_SET_ICTX(cmd->_header.trb, phys_addr);

        TRB_SET_TYPE(cmd->_header.trb, XHCI_TRB_TYPE_GET_PORT_BANDWIDTH_CMD);
        TRB_SET_SLOT(cmd->_header.trb, cmd->slot_id);
        TRB_SET_DEV_SPEED(cmd->_header.trb, cmd->device_speed);

        return enqueue_command(hc, cmd, 0, 0);
}

/* The table of command-issuing functions. */

typedef int (*cmd_handler) (xhci_hc_t *hc, xhci_cmd_t *cmd);

static cmd_handler cmd_handlers [] = {
        [XHCI_CMD_ENABLE_SLOT] = enable_slot_cmd,
        [XHCI_CMD_DISABLE_SLOT] = disable_slot_cmd,
        [XHCI_CMD_ADDRESS_DEVICE] = address_device_cmd,
        [XHCI_CMD_CONFIGURE_ENDPOINT] = configure_endpoint_cmd,
        [XHCI_CMD_EVALUATE_CONTEXT] = evaluate_context_cmd,
        [XHCI_CMD_RESET_ENDPOINT] = reset_endpoint_cmd,
        [XHCI_CMD_STOP_ENDPOINT] = stop_endpoint_cmd,
        [XHCI_CMD_SET_TR_DEQUEUE_POINTER] = set_tr_dequeue_pointer_cmd,
        [XHCI_CMD_RESET_DEVICE] = reset_device_cmd,
        // TODO: Force event (optional normative, for VMM, section 4.6.12).
        [XHCI_CMD_FORCE_EVENT] = NULL,
        // TODO: Negotiate bandwidth (optional normative, section 4.6.13).
        [XHCI_CMD_NEGOTIATE_BANDWIDTH] = NULL,
        // TODO: Set latency tolerance value (optional normative, section 4.6.14).
        [XHCI_CMD_SET_LATENCY_TOLERANCE_VALUE] = NULL,
        // TODO: Get port bandwidth (mandatory, but needs root hub implementation, section 4.6.15).
        [XHCI_CMD_GET_PORT_BANDWIDTH] = get_port_bandwidth_cmd,
        // TODO: Force header (mandatory, but needs root hub implementation, section 4.6.16).
        [XHCI_CMD_FORCE_HEADER] = NULL,
        [XHCI_CMD_NO_OP] = no_op_cmd
};

static int wait_for_cmd_completion(xhci_cmd_t *cmd)
{
        int rv = EOK;

        fibril_mutex_lock(&cmd->_header.completed_mtx);
        while (!cmd->_header.completed) {
                usb_log_debug2("Waiting for event completion: going to sleep.");
                rv = fibril_condvar_wait_timeout(&cmd->_header.completed_cv, &cmd->_header.completed_mtx, cmd->_header.timeout);

                usb_log_debug2("Waiting for event completion: woken: %s", str_error(rv));
                if (rv == ETIMEOUT) {
                        break;
                }
        }
        fibril_mutex_unlock(&cmd->_header.completed_mtx);

        return rv;
}

/** Issue command and block the current fibril until it is completed or timeout
 *  expires. Nothing is deallocated. Caller should always execute `xhci_cmd_fini`.
 */
int xhci_cmd_sync(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        assert(hc);
        assert(cmd);

        int err;

        if (!cmd_handlers[cmd->_header.cmd]) {
                /* Handler not implemented. */
                return ENOTSUP;
        }

        if ((err = cmd_handlers[cmd->_header.cmd](hc, cmd))) {
                /* Command could not be issued. */
                return err;
        }

        if ((err = wait_for_cmd_completion(cmd))) {
                /* Timeout expired or command failed. */
                return err;
        }

        return cmd->status == XHCI_TRBC_SUCCESS ? EOK : EINVAL;
}

/** Does the same thing as `xhci_cmd_sync` and executes `xhci_cmd_fini`. This
 *  is a useful shorthand for issuing commands without out parameters.
 */
int xhci_cmd_sync_fini(xhci_hc_t *hc, xhci_cmd_t *cmd)
{
        const int err = xhci_cmd_sync(hc, cmd);
        xhci_cmd_fini(cmd);

        return err;
}

/** Does the same thing as `xhci_cmd_sync_fini` without blocking the current
 *  fibril. The command is copied to stack memory and `fini` is called upon its completion.
 */
int xhci_cmd_async_fini(xhci_hc_t *hc, xhci_cmd_t *stack_cmd)
{
        assert(hc);
        assert(stack_cmd);

        /* Save the command for later. */
        xhci_cmd_t *heap_cmd = (xhci_cmd_t *) malloc(sizeof(xhci_cmd_t));
        if (!heap_cmd) {
                return ENOMEM;
        }

        /* TODO: Is this good for the mutex and the condvar? */
        memcpy(heap_cmd, stack_cmd, sizeof(xhci_cmd_t));
        heap_cmd->_header.async = true;

        /* Issue the command. */
        int err;

        if (!cmd_handlers[heap_cmd->_header.cmd]) {
                /* Handler not implemented. */
                err = ENOTSUP;
                goto err_heap_cmd;
        }

        if ((err = cmd_handlers[heap_cmd->_header.cmd](hc, heap_cmd))) {
                /* Command could not be issued. */
                goto err_heap_cmd;
        }

        return EOK;

err_heap_cmd:
        free(heap_cmd);
        return err;
}

/**
 * @}
 */