/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
                 2011,2012 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @file    usb.c
 * @brief   USB Driver code.
 *
 * @addtogroup USB
 * @{
 */

#include <string.h>

#include "ch.h"
#include "hal.h"
#include "usb.h"

#if HAL_USE_USB || defined(__DOXYGEN__)

/*===========================================================================*/
/* Driver local definitions.                                                 */
/*===========================================================================*/

/*===========================================================================*/
/* Driver exported variables.                                                */
/*===========================================================================*/

/*===========================================================================*/
/* Driver local variables.                                                   */
/*===========================================================================*/

static const uint8_t zero_status[] = {0x00, 0x00};
static const uint8_t active_status[] ={0x00, 0x00};
static const uint8_t halted_status[] = {0x01, 0x00};

/*===========================================================================*/
/* Driver local functions.                                                   */
/*===========================================================================*/

/**
 * @brief  SET ADDRESS transaction callback.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 */
static void set_address(USBDriver *usbp) {

  usbp->address = usbp->setup[2];
  usb_lld_set_address(usbp);
  _usb_isr_invoke_event_cb(usbp, USB_EVENT_ADDRESS);
  usbp->state = USB_SELECTED;
}

/**
 * @brief   Standard requests handler.
 * @details This is the standard requests default handler, most standard
 *          requests are handled here, the user can override the standard
 *          handling using the @p requests_hook_cb hook in the
 *          @p USBConfig structure.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @return              The request handling exit code.
 * @retval FALSE        Request not recognized by the handler or error.
 * @retval TRUE         Request handled.
 */
static bool_t default_handler(USBDriver *usbp) {
  const USBDescriptor *dp;

  /* Decoding the request.*/
  switch (((usbp->setup[0] & (USB_RTYPE_RECIPIENT_MASK |
                              USB_RTYPE_TYPE_MASK)) |
           (usbp->setup[1] << 8))) {
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_GET_STATUS << 8):
    /* Just returns the current status word.*/
    usbSetupTransfer(usbp, (uint8_t *)&usbp->status, 2, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_CLEAR_FEATURE << 8):
    /* Only the DEVICE_REMOTE_WAKEUP is handled here, any other feature
       number is handled as an error.*/
    if (usbp->setup[2] == USB_FEATURE_DEVICE_REMOTE_WAKEUP) {
      usbp->status &= ~2;
      usbSetupTransfer(usbp, NULL, 0, NULL);
      return TRUE;
    }
    return FALSE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_SET_FEATURE << 8):
    /* Only the DEVICE_REMOTE_WAKEUP is handled here, any other feature
       number is handled as an error.*/
    if (usbp->setup[2] == USB_FEATURE_DEVICE_REMOTE_WAKEUP) {
      usbp->status |= 2;
      usbSetupTransfer(usbp, NULL, 0, NULL);
      return TRUE;
    }
    return FALSE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_SET_ADDRESS << 8):
    /* The SET_ADDRESS handling can be performed here or postponed after
       the status packed depending on the USB_SET_ADDRESS_MODE low
       driver setting.*/
#if USB_SET_ADDRESS_MODE == USB_EARLY_SET_ADDRESS
    if ((usbp->setup[0] == USB_RTYPE_RECIPIENT_DEVICE) &&
        (usbp->setup[1] == USB_REQ_SET_ADDRESS))
      set_address(usbp);
    usbSetupTransfer(usbp, NULL, 0, NULL);
#else
    usbSetupTransfer(usbp, NULL, 0, set_address);
#endif
    return TRUE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_GET_DESCRIPTOR << 8):
    /* Handling descriptor requests from the host.*/
    dp = usbp->config->get_descriptor_cb(
           usbp, usbp->setup[3], usbp->setup[2],
           usbFetchWord(&usbp->setup[4]));
    if (dp == NULL)
      return FALSE;
    usbSetupTransfer(usbp, (uint8_t *)dp->ud_string, dp->ud_size, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_GET_CONFIGURATION << 8):
    /* Returning the last selected configuration.*/
    usbSetupTransfer(usbp, &usbp->configuration, 1, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_SET_CONFIGURATION << 8):
    /* Handling configuration selection from the host.*/
    usbp->configuration = usbp->setup[2];
    if (usbp->configuration == 0)
      usbp->state = USB_SELECTED;
    else
      usbp->state = USB_ACTIVE;
    _usb_isr_invoke_event_cb(usbp, USB_EVENT_CONFIGURED);
    usbSetupTransfer(usbp, NULL, 0, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_INTERFACE | (USB_REQ_GET_STATUS << 8):
  case USB_RTYPE_RECIPIENT_ENDPOINT | (USB_REQ_SYNCH_FRAME << 8):
    /* Just sending two zero bytes, the application can change the behavior
       using a hook..*/
    usbSetupTransfer(usbp, (uint8_t *)zero_status, 2, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_ENDPOINT | (USB_REQ_GET_STATUS << 8):
    /* Sending the EP status.*/
    if (usbp->setup[4] & 0x80) {
      switch (usb_lld_get_status_in(usbp, usbp->setup[4] & 0x0F)) {
      case EP_STATUS_STALLED:
        usbSetupTransfer(usbp, (uint8_t *)halted_status, 2, NULL);
        return TRUE;
      case EP_STATUS_ACTIVE:
        usbSetupTransfer(usbp, (uint8_t *)active_status, 2, NULL);
        return TRUE;
      default:
        return FALSE;
      }
    }
    else {
      switch (usb_lld_get_status_out(usbp, usbp->setup[4] & 0x0F)) {
      case EP_STATUS_STALLED:
        usbSetupTransfer(usbp, (uint8_t *)halted_status, 2, NULL);
        return TRUE;
      case EP_STATUS_ACTIVE:
        usbSetupTransfer(usbp, (uint8_t *)active_status, 2, NULL);
        return TRUE;
      default:
        return FALSE;
      }
    }
  case USB_RTYPE_RECIPIENT_ENDPOINT | (USB_REQ_CLEAR_FEATURE << 8):
    /* Only ENDPOINT_HALT is handled as feature.*/
    if (usbp->setup[2] != USB_FEATURE_ENDPOINT_HALT)
      return FALSE;
    /* Clearing the EP status, not valid for EP0, it is ignored in that case.*/
    if ((usbp->setup[4] & 0x0F) > 0) {
      if (usbp->setup[4] & 0x80)
        usb_lld_clear_in(usbp, usbp->setup[4] & 0x0F);
      else
        usb_lld_clear_out(usbp, usbp->setup[4] & 0x0F);
    }
    usbSetupTransfer(usbp, NULL, 0, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_ENDPOINT | (USB_REQ_SET_FEATURE << 8):
    /* Only ENDPOINT_HALT is handled as feature.*/
    if (usbp->setup[2] != USB_FEATURE_ENDPOINT_HALT)
      return FALSE;
    /* Stalling the EP, not valid for EP0, it is ignored in that case.*/
    if ((usbp->setup[4] & 0x0F) > 0) {
      if (usbp->setup[4] & 0x80)
        usb_lld_stall_in(usbp, usbp->setup[4] & 0x0F);
      else
        usb_lld_stall_out(usbp, usbp->setup[4] & 0x0F);
    }
    usbSetupTransfer(usbp, NULL, 0, NULL);
    return TRUE;
  case USB_RTYPE_RECIPIENT_DEVICE | (USB_REQ_SET_DESCRIPTOR << 8):
  case USB_RTYPE_RECIPIENT_INTERFACE | (USB_REQ_CLEAR_FEATURE << 8):
  case USB_RTYPE_RECIPIENT_INTERFACE | (USB_REQ_SET_FEATURE << 8):
  case USB_RTYPE_RECIPIENT_INTERFACE | (USB_REQ_GET_INTERFACE << 8):
  case USB_RTYPE_RECIPIENT_INTERFACE | (USB_REQ_SET_INTERFACE << 8):
    /* All the above requests are not handled here, if you need them then
       use the hook mechanism and provide handling.*/
  default:
    return FALSE;
  }
}

/*===========================================================================*/
/* Driver exported functions.                                                */
/*===========================================================================*/

/**
 * @brief   USB Driver initialization.
 * @note    This function is implicitly invoked by @p halInit(), there is
 *          no need to explicitly initialize the driver.
 *
 * @init
 */
void usbInit(void) {

  usb_lld_init();
}

/**
 * @brief   Initializes the standard part of a @p USBDriver structure.
 *
 * @param[out] usbp     pointer to the @p USBDriver object
 *
 * @init
 */
void usbObjectInit(USBDriver *usbp) {

  usbp->state        = USB_STOP;
  usbp->config       = NULL;
  usbp->param        = NULL;
  usbp->transmitting = 0;
  usbp->receiving    = 0;
}

/**
 * @brief   Configures and activates the USB peripheral.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] config    pointer to the @p USBConfig object
 *
 * @api
 */
void usbStart(USBDriver *usbp, const USBConfig *config) {
  unsigned i;

  chDbgCheck((usbp != NULL) && (config != NULL), "usbStart");

  chSysLock();
  chDbgAssert((usbp->state == USB_STOP) || (usbp->state == USB_READY),
              "usbStart(), #1", "invalid state");
  usbp->config = config;
  for (i = 0; i <= USB_MAX_ENDPOINTS; i++)
    usbp->epc[i] = NULL;
  usb_lld_start(usbp);
  usbp->state = USB_READY;
  chSysUnlock();
}

/**
 * @brief   Deactivates the USB peripheral.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 *
 * @api
 */
void usbStop(USBDriver *usbp) {

  chDbgCheck(usbp != NULL, "usbStop");

  chSysLock();
  chDbgAssert((usbp->state == USB_STOP) || (usbp->state == USB_READY),
              "usbStop(), #1", "invalid state");
  usb_lld_stop(usbp);
  usbp->state = USB_STOP;
  chSysUnlock();
}

/**
 * @brief   Enables an endpoint.
 * @details This function enables an endpoint, both IN and/or OUT directions
 *          depending on the configuration structure.
 * @note    This function must be invoked in response of a SET_CONFIGURATION
 *          or SET_INTERFACE message.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 * @param[in] epcp      the endpoint configuration
 *
 * @iclass
 */
void usbInitEndpointI(USBDriver *usbp, usbep_t ep,
                      const USBEndpointConfig *epcp) {

  chDbgCheckClassI();
  chDbgCheck((usbp != NULL) && (epcp != NULL), "usbInitEndpointI");
  chDbgAssert(usbp->state == USB_ACTIVE,
              "usbEnableEndpointI(), #1", "invalid state");
  chDbgAssert(usbp->epc[ep] == NULL,
              "usbEnableEndpointI(), #2", "already initialized");

  /* Logically enabling the endpoint in the USBDriver structure.*/
  if (epcp->in_state != NULL)
    memset(epcp->in_state, 0, sizeof(USBInEndpointState));
  if (epcp->out_state != NULL)
    memset(epcp->out_state, 0, sizeof(USBOutEndpointState));

  usbp->epc[ep] = epcp;

  /* Low level endpoint activation.*/
  usb_lld_init_endpoint(usbp, ep);
}

/**
 * @brief   Disables all the active endpoints.
 * @details This function disables all the active endpoints except the
 *          endpoint zero.
 * @note    This function must be invoked in response of a SET_CONFIGURATION
 *          message with configuration number zero.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 *
 * @iclass
 */
void usbDisableEndpointsI(USBDriver *usbp) {
  unsigned i;

  chDbgCheckClassI();
  chDbgCheck(usbp != NULL, "usbDisableEndpointsI");
  chDbgAssert(usbp->state == USB_SELECTED,
              "usbDisableEndpointsI(), #1", "invalid state");

  usbp->transmitting &= ~1;
  usbp->receiving    &= ~1;
  for (i = 1; i <= USB_MAX_ENDPOINTS; i++)
    usbp->epc[i] = NULL;

  /* Low level endpoints deactivation.*/
  usb_lld_disable_endpoints(usbp);
}

/**
 * @brief   Prepares for a receive transaction on an OUT endpoint.
 * @post    The endpoint is ready for @p usbStartReceiveI().
 * @note    This function can be called both in ISR and thread context.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 * @param[out] buf      buffer where to copy the received data
 * @param[in] n         transaction size
 *
 * @special
 */
void usbPrepareReceive(USBDriver *usbp, usbep_t ep, uint8_t *buf, size_t n) {
  USBOutEndpointState *osp = usbp->epc[ep]->out_state;

  osp->rxqueued           = FALSE;
  osp->mode.linear.rxbuf  = buf;
  osp->rxsize             = n;
  osp->rxcnt              = 0;

  usb_lld_prepare_receive(usbp, ep);
}

/**
 * @brief   Prepares for a transmit transaction on an IN endpoint.
 * @post    The endpoint is ready for @p usbStartTransmitI().
 * @note    This function can be called both in ISR and thread context.
 * @note    The queue must contain at least the amount of data specified
 *          as transaction size.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 * @param[in] buf       buffer where to fetch the data to be transmitted
 * @param[in] n         transaction size
 *
 * @special
 */
void usbPrepareTransmit(USBDriver *usbp, usbep_t ep,
                        const uint8_t *buf, size_t n) {
  USBInEndpointState *isp = usbp->epc[ep]->in_state;

  isp->txqueued           = FALSE;
  isp->mode.linear.txbuf  = buf;
  isp->txsize             = n;
  isp->txcnt              = 0;

  usb_lld_prepare_transmit(usbp, ep);
}

/**
 * @brief   Prepares for a receive transaction on an OUT endpoint.
 * @post    The endpoint is ready for @p usbStartReceiveI().
 * @note    This function can be called both in ISR and thread context.
 * @note    The queue must have enough free space to accommodate the
 *          specified transaction size rounded to the next packet size
 *          boundary. For example if the transaction size is 1 and the
 *          packet size is 64 then the queue must have space for at least
 *          64 bytes.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 * @param[in] iqp       input queue to be filled with incoming data
 * @param[in] n         transaction size
 *
 * @special
 */
void usbPrepareQueuedReceive(USBDriver *usbp, usbep_t ep,
                             InputQueue *iqp, size_t n) {
  USBOutEndpointState *osp = usbp->epc[ep]->out_state;

  osp->rxqueued           = TRUE;
  osp->mode.queue.rxqueue = iqp;
  osp->rxsize             = n;
  osp->rxcnt              = 0;

  usb_lld_prepare_receive(usbp, ep);
}

/**
 * @brief   Prepares for a transmit transaction on an IN endpoint.
 * @post    The endpoint is ready for @p usbStartTransmitI().
 * @note    This function can be called both in ISR and thread context.
 * @note    The transmit transaction size is equal to the data contained
 *          in the queue.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 * @param[in] oqp       output queue to be fetched for outgoing data
 * @param[in] n         transaction size
 *
 * @special
 */
void usbPrepareQueuedTransmit(USBDriver *usbp, usbep_t ep,
                              OutputQueue *oqp, size_t n) {
  USBInEndpointState *isp = usbp->epc[ep]->in_state;

  isp->txqueued           = TRUE;
  isp->mode.queue.txqueue = oqp;
  isp->txsize             = n;
  isp->txcnt              = 0;

  usb_lld_prepare_transmit(usbp, ep);
}

/**
 * @brief   Starts a receive transaction on an OUT endpoint.
 * @post    The endpoint callback is invoked when the transfer has been
 *          completed.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 *
 * @return              The operation status.
 * @retval FALSE        Operation started successfully.
 * @retval TRUE         Endpoint busy, operation not started.
 *
 * @iclass
 */
bool_t usbStartReceiveI(USBDriver *usbp, usbep_t ep) {

  chDbgCheckClassI();
  chDbgCheck(usbp != NULL, "usbStartReceiveI");

  if (usbGetReceiveStatusI(usbp, ep))
    return TRUE;

  usbp->receiving |= (1 << ep);
  usb_lld_start_out(usbp, ep);
  return FALSE;
}

/**
 * @brief   Starts a transmit transaction on an IN endpoint.
 * @post    The endpoint callback is invoked when the transfer has been
 *          completed.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 *
 * @return              The operation status.
 * @retval FALSE        Operation started successfully.
 * @retval TRUE         Endpoint busy, operation not started.
 *
 * @iclass
 */
bool_t usbStartTransmitI(USBDriver *usbp, usbep_t ep) {

  chDbgCheckClassI();
  chDbgCheck(usbp != NULL, "usbStartTransmitI");

  if (usbGetTransmitStatusI(usbp, ep))
    return TRUE;

  usbp->transmitting |= (1 << ep);
  usb_lld_start_in(usbp, ep);
  return FALSE;
}

/**
 * @brief   Stalls an OUT endpoint.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 *
 * @return              The operation status.
 * @retval FALSE        Endpoint stalled.
 * @retval TRUE         Endpoint busy, not stalled.
 *
 * @iclass
 */
bool_t usbStallReceiveI(USBDriver *usbp, usbep_t ep) {

  chDbgCheckClassI();
  chDbgCheck(usbp != NULL, "usbStallReceiveI");

  if (usbGetReceiveStatusI(usbp, ep))
    return TRUE;

  usb_lld_stall_out(usbp, ep);
  return FALSE;
}

/**
 * @brief   Stalls an IN endpoint.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number
 *
 * @return              The operation status.
 * @retval FALSE        Endpoint stalled.
 * @retval TRUE         Endpoint busy, not stalled.
 *
 * @iclass
 */
bool_t usbStallTransmitI(USBDriver *usbp, usbep_t ep) {

  chDbgCheckClassI();
  chDbgCheck(usbp != NULL, "usbStallTransmitI");

  if (usbGetTransmitStatusI(usbp, ep))
    return TRUE;

  usb_lld_stall_in(usbp, ep);
  return FALSE;
}

/**
 * @brief   USB reset routine.
 * @details This function must be invoked when an USB bus reset condition is
 *          detected.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 *
 * @notapi
 */
void _usb_reset(USBDriver *usbp) {
  unsigned i;

  usbp->state         = USB_READY;
  usbp->status        = 0;
  usbp->address       = 0;
  usbp->configuration = 0;
  usbp->transmitting  = 0;
  usbp->receiving     = 0;

  /* Invalidates all endpoints into the USBDriver structure.*/
  for (i = 0; i <= USB_MAX_ENDPOINTS; i++)
    usbp->epc[i] = NULL;

  /* EP0 state machine initialization.*/
  usbp->ep0state = USB_EP0_WAITING_SETUP;

  /* Low level reset.*/
  usb_lld_reset(usbp);
}

/**
 * @brief   Default EP0 SETUP callback.
 * @details This function is used by the low level driver as default handler
 *          for EP0 SETUP events.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number, always zero
 *
 * @notapi
 */
void _usb_ep0setup(USBDriver *usbp, usbep_t ep) {
  size_t max;

  usbp->ep0state = USB_EP0_WAITING_SETUP;
  usbReadSetup(usbp, ep, usbp->setup);

  /* First verify if the application has an handler installed for this
     request.*/
  if (!(usbp->config->requests_hook_cb) ||
      !(usbp->config->requests_hook_cb(usbp))) {
    /* Invoking the default handler, if this fails then stalls the
       endpoint zero as error.*/
    if (((usbp->setup[0] & USB_RTYPE_TYPE_MASK) != USB_RTYPE_TYPE_STD) ||
        !default_handler(usbp)) {
      /* Error response, the state machine goes into an error state, the low
         level layer will have to reset it to USB_EP0_WAITING_SETUP after
         receiving a SETUP packet.*/
      usb_lld_stall_in(usbp, 0);
      usb_lld_stall_out(usbp, 0);
      _usb_isr_invoke_event_cb(usbp, USB_EVENT_STALLED);
      usbp->ep0state = USB_EP0_ERROR;
      return;
    }
  }

  /* Transfer preparation. The request handler must have populated
     correctly the fields ep0next, ep0n and ep0endcb using the macro
     usbSetupTransfer().*/
  max = usbFetchWord(&usbp->setup[6]);
  /* The transfer size cannot exceed the specified amount.*/
  if (usbp->ep0n > max)
    usbp->ep0n = max;
  if ((usbp->setup[0] & USB_RTYPE_DIR_MASK) == USB_RTYPE_DIR_DEV2HOST) {
    /* IN phase.*/
    if (usbp->ep0n > 0) {
      /* Starts the transmit phase.*/
      usbp->ep0state = USB_EP0_TX;
      usbPrepareTransmit(usbp, 0, usbp->ep0next, usbp->ep0n);
      chSysLockFromIsr();
      usbStartTransmitI(usbp, 0);
      chSysUnlockFromIsr();
    }
    else {
      /* No transmission phase, directly receiving the zero sized status
         packet.*/
      usbp->ep0state = USB_EP0_WAITING_STS;
      usbPrepareReceive(usbp, 0, NULL, 0);
      chSysLockFromIsr();
      usbStartReceiveI(usbp, 0);
      chSysUnlockFromIsr();
    }
  }
  else {
    /* OUT phase.*/
    if (usbp->ep0n > 0) {
      /* Starts the receive phase.*/
      usbp->ep0state = USB_EP0_RX;
      usbPrepareReceive(usbp, 0, usbp->ep0next, usbp->ep0n);
      chSysLockFromIsr();
      usbStartReceiveI(usbp, 0);
      chSysUnlockFromIsr();
    }
    else {
      /* No receive phase, directly sending the zero sized status
         packet.*/
      usbp->ep0state = USB_EP0_SENDING_STS;
      usbPrepareTransmit(usbp, 0, NULL, 0);
      chSysLockFromIsr();
      usbStartTransmitI(usbp, 0);
      chSysUnlockFromIsr();
    }
  }
}

/**
 * @brief   Default EP0 IN callback.
 * @details This function is used by the low level driver as default handler
 *          for EP0 IN events.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number, always zero
 *
 * @notapi
 */
void _usb_ep0in(USBDriver *usbp, usbep_t ep) {
  size_t max;

  (void)ep;
  switch (usbp->ep0state) {
  case USB_EP0_TX:
    max = usbFetchWord(&usbp->setup[6]);
    /* If the transmitted size is less than the requested size and it is a
       multiple of the maximum packet size then a zero size packet must be
       transmitted.*/
    if ((usbp->ep0n < max) &&
        ((usbp->ep0n % usbp->epc[0]->in_maxsize) == 0)) {
      usbPrepareTransmit(usbp, 0, NULL, 0);
      chSysLockFromIsr();
      usbStartTransmitI(usbp, 0);
      chSysUnlockFromIsr();
      return;
    }

    /* Transmit phase over, receiving the zero sized status packet.*/
    usbp->ep0state = USB_EP0_WAITING_STS;
    usbPrepareReceive(usbp, 0, NULL, 0);
    chSysLockFromIsr();
    usbStartReceiveI(usbp, 0);
    chSysUnlockFromIsr();
    return;
  case USB_EP0_SENDING_STS:
    /* Status packet sent, invoking the callback if defined.*/
    if (usbp->ep0endcb != NULL)
      usbp->ep0endcb(usbp);
    usbp->ep0state = USB_EP0_WAITING_SETUP;
    return;
  default:
    ;
  }
  /* Error response, the state machine goes into an error state, the low
     level layer will have to reset it to USB_EP0_WAITING_SETUP after
     receiving a SETUP packet.*/
  usb_lld_stall_in(usbp, 0);
  usb_lld_stall_out(usbp, 0);
  _usb_isr_invoke_event_cb(usbp, USB_EVENT_STALLED);
  usbp->ep0state = USB_EP0_ERROR;
}

/**
 * @brief   Default EP0 OUT callback.
 * @details This function is used by the low level driver as default handler
 *          for EP0 OUT events.
 *
 * @param[in] usbp      pointer to the @p USBDriver object
 * @param[in] ep        endpoint number, always zero
 *
 * @notapi
 */
void _usb_ep0out(USBDriver *usbp, usbep_t ep) {

  (void)ep;
  switch (usbp->ep0state) {
  case USB_EP0_RX:
    /* Receive phase over, sending the zero sized status packet.*/
    usbp->ep0state = USB_EP0_SENDING_STS;
    usbPrepareTransmit(usbp, 0, NULL, 0);
    chSysLockFromIsr();
    usbStartTransmitI(usbp, 0);
    chSysUnlockFromIsr();
    return;
  case USB_EP0_WAITING_STS:
    /* Status packet received, it must be zero sized, invoking the callback
       if defined.*/
    if (usbGetReceiveTransactionSizeI(usbp, 0) != 0)
      break;
    if (usbp->ep0endcb != NULL)
      usbp->ep0endcb(usbp);
    usbp->ep0state = USB_EP0_WAITING_SETUP;
    return;
  default:
    ;
  }
  /* Error response, the state machine goes into an error state, the low
     level layer will have to reset it to USB_EP0_WAITING_SETUP after
     receiving a SETUP packet.*/
  usb_lld_stall_in(usbp, 0);
  usb_lld_stall_out(usbp, 0);
  _usb_isr_invoke_event_cb(usbp, USB_EVENT_STALLED);
  usbp->ep0state = USB_EP0_ERROR;
}

#endif /* HAL_USE_USB */

/** @} */