Function sim_usbdev_epread

arch/sim/src/sim/sim_usbdev.c:527–588

 ****************************************************************************/

static int sim_usbdev_epread(uint16_t addr, uint8_t *data, uint16_t len)
{
  struct sim_usbdev_s *priv = &g_sim_usbdev;
  struct sim_ep_s *privep;
  struct sim_req_s *privreq;
  uint8_t *dest;
  uint8_t epno;
  int readlen;

  /* Get the unadorned endpoint number */

  epno = USB_EPNO(addr);
  privep = &priv->eps[epno];

  usbtrace(TRACE_READ(USB_EPNO(privep->ep.eplog)), len);

  /* We get here when an IN endpoint interrupt occurs.  So now we know that
   * there is no TX transfer in progress.
   */

  while (privep->epstate == SIM_EPSTATE_IDLE && len > 0)
    {
      /* Check the request from the head of the endpoint request queue */

      privreq = sim_rqpeek(&privep->reqq);
      if (!privreq)
        {
          return -ENOENT;
        }

      /* Get the source and destination transfer addresses */

      dest = privreq->req.buf + privreq->req.xfrd;

      /* Get the number of bytes to read from packet memory */

      readlen = MIN(privreq->req.len - privreq->req.xfrd, len);

      /* Receive the next packet */

      memcpy(dest, data, readlen);

      /* If the receive buffer is full or this is a partial packet,
       * then we are finished with the request buffer).
       */

      privreq->req.xfrd += readlen;
      len -= readlen;
      data += readlen;

      if (len < privep->ep.maxpacket ||
          privreq->req.xfrd >= privreq->req.len)
        {
          /* Return the read request to the class driver. */

          usbtrace(TRACE_COMPLETE(epno), privreq->req.xfrd);
          sim_reqcomplete(privep, OK);
        }