Example #1
0
/**
  Process the events on the port.

  @param  HubIf                 The HUB that has the device connected.
  @param  Port                  The port index of the hub (started with zero).

  @retval EFI_SUCCESS           The device is enumerated (added or removed).
  @retval EFI_OUT_OF_RESOURCES  Failed to allocate resource for the device.
  @retval Others                Failed to enumerate the device.

**/
EFI_STATUS
UsbEnumeratePort (
  IN USB_INTERFACE        *HubIf,
  IN UINT8                Port
  )
{
  USB_HUB_API             *HubApi;
  USB_DEVICE              *Child;
  EFI_USB_PORT_STATUS     PortState;
  EFI_STATUS              Status;

  Child   = NULL;
  HubApi  = HubIf->HubApi;

  //
  // Host learns of the new device by polling the hub for port changes.
  //
  Status = HubApi->GetPortStatus (HubIf, Port, &PortState);

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumeratePort: failed to get state of port %d\n", Port));
    DBG("UsbEnumeratePort: failed to get state of port %d\n", Port);
    return Status;
  }

  //
  // Only handle connection/enable/overcurrent/reset change.
  // Usb super speed hub may report other changes, such as warm reset change. Ignore them.
  //
  if ((PortState.PortChangeStatus & (USB_PORT_STAT_C_CONNECTION | USB_PORT_STAT_C_ENABLE | USB_PORT_STAT_C_OVERCURRENT | USB_PORT_STAT_C_RESET)) == 0) {
    return EFI_SUCCESS;
  }

//  DEBUG (( EFI_D_INFO, "UsbEnumeratePort: port %d state - %02x, change - %02x on %p\n",
//Port, PortState.PortStatus, PortState.PortChangeStatus, HubIf));
  DBG( "UsbEnumeratePort: port %d state - %02x, change - %02x on %p\n",
      Port, PortState.PortStatus, PortState.PortChangeStatus, HubIf);
  //
  // This driver only process two kinds of events now: over current and
  // connect/disconnect. Other three events are: ENABLE, SUSPEND, RESET.
  // ENABLE/RESET is used to reset port. SUSPEND isn't supported.
  //
  
  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_OVERCURRENT)) {     

    if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_OVERCURRENT)) {
      //
      // Case1:
      //   Both OverCurrent and OverCurrentChange set, means over current occurs, 
      //   which probably is caused by short circuit. It has to wait system hardware
      //   to perform recovery.
      //
 //     DEBUG (( EFI_D_ERROR, "UsbEnumeratePort: Critical Over Current\n", Port));
      DBG("UsbEnumeratePort: Critical Over Current\n", Port);
      return EFI_DEVICE_ERROR;
      
    } 
    //
    // Case2:
    //   Only OverCurrentChange set, means system has been recoveried from 
    //   over current. As a result, all ports are nearly power-off, so
    //   it's necessary to detach and enumerate all ports again. 
    //
//    DEBUG (( EFI_D_ERROR, "UsbEnumeratePort: 2.0 device Recovery Over Current\n", Port));
    DBG("UsbEnumeratePort: 2.0 device Recovery Over Current\n", Port);
  }

  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_ENABLE)) {  
    //
    // Case3:
    //   1.1 roothub port reg doesn't reflect over-current state, while its counterpart
    //   on 2.0 roothub does. When over-current has influence on 1.1 device, the port 
    //   would be disabled, so it's also necessary to detach and enumerate again.
    //
//    DEBUG (( EFI_D_ERROR, "UsbEnumeratePort: 1.1 device Recovery Over Current\n", Port));
    DBG("UsbEnumeratePort: 1.1 device Recovery Over Current\n", Port);
  }
  
  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_CONNECTION)) {
    //
    // Case4:
    //   Device connected or disconnected normally. 
    //
//    DEBUG ((EFI_D_ERROR, "UsbEnumeratePort: Device Connect/Discount Normally\n", Port));
    DBG("UsbEnumeratePort: Device Connect/Discount Normally\n");
  }

  // 
  // Following as the above cases, it's safety to remove and create again.
  //
  Child = UsbFindChild (HubIf, Port);
  
  if (Child != NULL) {
//    DEBUG (( EFI_D_INFO, "UsbEnumeratePort: device at port %d removed from root hub %p\n", Port, HubIf));
    DBG("UsbEnumeratePort: device at port %d removed from root hub %p\n", Port, HubIf);
    UsbRemoveDevice (Child);
  }
  
  if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_CONNECTION)) {
    //
    // Now, new device connected, enumerate and configure the device 
    //
//   DEBUG (( EFI_D_INFO, "UsbEnumeratePort: new device connected at port %d\n", Port));
    DBG("UsbEnumeratePort: new device connected at port %d\n", Port);
    Status = UsbEnumerateNewDev (HubIf, Port);
  
  } else {
//    DEBUG (( EFI_D_INFO, "UsbEnumeratePort: device disconnected event on port %d\n", Port));
    DBG("UsbEnumeratePort: device disconnected event on port %d status=0x%x\n", Port, PortState.PortStatus);
  }
  
  HubApi->ClearPortChange (HubIf, Port);
  DBG("ClearPortChange\n");
  return Status;
}
Example #2
0
STATIC
EFI_STATUS
UsbEnumeratePort (
  IN USB_INTERFACE        *HubIf,
  IN UINT8                Port
  )
/*++

Routine Description:

  Process the events on the port.

Arguments:

  HubIf - The HUB that has the device connected
  Port  - The port index of the hub (started with zero)

Returns:

  EFI_SUCCESS          - The device is enumerated (added or removed)
  EFI_OUT_OF_RESOURCES - Failed to allocate resource for the device
  Others               - Failed to enumerate the device

--*/
{
  USB_HUB_API             *HubApi;
  USB_DEVICE              *Child;
  EFI_USB_PORT_STATUS     PortState;
  EFI_STATUS              Status;

  Child   = NULL;
  HubApi  = HubIf->HubApi;
  
  //
  // Host learns of the new device by polling the hub for port changes.
  //
  Status = HubApi->GetPortStatus (HubIf, Port, &PortState);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumeratePort: failed to get state of port %d\n", Port));
    return Status;
  }

  if (PortState.PortChangeStatus == 0) {
    return EFI_SUCCESS;
  }

  USB_DEBUG (("UsbEnumeratePort: port %d state - %x, change - %x\n", 
              Port, PortState.PortStatus, PortState.PortChangeStatus));

  //
  // This driver only process two kinds of events now: over current and 
  // connect/disconnect. Other three events are: ENABLE, SUSPEND, RESET.
  // ENABLE/RESET is used to reset port. SUSPEND isn't supported.
  //
  
  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_OVERCURRENT)) {     

    if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_OVERCURRENT)) {
      //
      // Case1:
      //   Both OverCurrent and OverCurrentChange set, means over current occurs, 
      //   which probably is caused by short circuit. It has to wait system hardware
      //   to perform recovery.
      //
      USB_DEBUG (("UsbEnumeratePort: Critical Over Current\n", Port));
      return EFI_DEVICE_ERROR;
      
    } 
    //
    // Case2:
    //   Only OverCurrentChange set, means system has been recoveried from 
    //   over current. As a result, all ports are nearly power-off, so
    //   it's necessary to detach and enumerate all ports again. 
    //
    USB_DEBUG (("UsbEnumeratePort: 2.0 Device Recovery Over Current\n", Port)); 
  }

  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_ENABLE)) {  
    //
    // Case3:
    //   1.1 roothub port reg doesn't reflect over-current state, while its counterpart
    //   on 2.0 roothub does. When over-current has influence on 1.1 device, the port 
    //   would be disabled, so it's also necessary to detach and enumerate again.
    //
    USB_DEBUG (("UsbEnumeratePort: 1.1 Device Recovery Over Current\n", Port));
  }
  
  if (USB_BIT_IS_SET (PortState.PortChangeStatus, USB_PORT_STAT_C_CONNECTION)) {
    //
    // Case4:
    //   Device connected or disconnected normally. 
    //
    USB_DEBUG (("UsbEnumeratePort: Device Connect/Discount Normally\n", Port));
  }

  // 
  // Following as the above cases, it's safety to remove and create again.
  //
  Child = UsbFindChild (HubIf, Port);
  
  if (Child != NULL) {
    USB_DEBUG (("UsbEnumeratePort: device at port %d removed from system\n", Port));
    UsbRemoveDevice (Child);
  }
  
  if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_CONNECTION)) {
    //
    // Now, new device connected, enumerate and configure the device 
    //
    USB_DEBUG (("UsbEnumeratePort: new device connected at port %d\n", Port));
    Status = UsbEnumerateNewDev (HubIf, Port);
  
  } else {
    USB_DEBUG (("UsbEnumeratePort: device disconnected event on port %d\n", Port));
  }
  
  HubApi->ClearPortChange (HubIf, Port);
  return Status;
}
Example #3
0
/**
  Enumerate and configure the new device on the port of this HUB interface.

  @param  HubIf                 The HUB that has the device connected.
  @param  Port                  The port index of the hub (started with zero).

  @retval EFI_SUCCESS           The device is enumerated (added or removed).
  @retval EFI_OUT_OF_RESOURCES  Failed to allocate resource for the device.
  @retval Others                Failed to enumerate the device.

**/
EFI_STATUS
UsbEnumerateNewDev (
  IN USB_INTERFACE        *HubIf,
  IN UINT8                Port
  )
{
  USB_BUS                 *Bus;
  USB_HUB_API             *HubApi;
  USB_DEVICE              *Child;
  USB_DEVICE              *Parent;
  EFI_USB_PORT_STATUS     PortState;
  UINTN                   Address;
  UINT8                   Config;
  EFI_STATUS              Status;

  Parent  = HubIf->Device;
  Bus     = Parent->Bus;
  HubApi  = HubIf->HubApi;  
  Address = Bus->MaxDevices;
  DBG("USB_WAIT_PORT_STABLE_STALL\n");
  gBS->Stall (USB_WAIT_PORT_STABLE_STALL); //100ms
  
  //
  // Hub resets the device for at least 10 milliseconds.
  // Host learns device speed. If device is of low/full speed
  // and the hub is a EHCI root hub, ResetPort will release
  // the device to its companion UHCI and return an error.
  //
  Status = HubApi->ResetPort (HubIf, Port);

  if (EFI_ERROR (Status)) {
 //   DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to reset port %d - %r\n", Port, Status));

    return Status;
  }

//  DEBUG (( EFI_D_INFO, "UsbEnumerateNewDev: hub port %d is reset\n", Port));

  Child = UsbCreateDevice (HubIf, Port);

  if (Child == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // OK, now identify the device speed. After reset, hub
  // fully knows the actual device speed.
  //
  DBG("GetPortStatus\n");
  Status = HubApi->GetPortStatus (HubIf, Port, &PortState);

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to get speed of port %d\n", Port));
    goto ON_ERROR;
  }

  if (!USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_CONNECTION)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: No device presented at port %d\n", Port));
    goto ON_ERROR;
  } else if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_SUPER_SPEED)){
    Child->Speed      = EFI_USB_SPEED_SUPER;
    Child->MaxPacket0 = 512;
  } else if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_HIGH_SPEED)) {
    Child->Speed      = EFI_USB_SPEED_HIGH;
    Child->MaxPacket0 = 64;
  } else if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_LOW_SPEED)) {
    Child->Speed      = EFI_USB_SPEED_LOW;
    Child->MaxPacket0 = 8;
  } else {
    Child->Speed      = EFI_USB_SPEED_FULL;
    Child->MaxPacket0 = 8;
  }

//  DEBUG (( EFI_D_INFO, "UsbEnumerateNewDev: device is of %d speed\n", Child->Speed));
  DBG("UsbEnumerateNewDev: device is of %d speed\n", Child->Speed);
  if (((Child->Speed == EFI_USB_SPEED_LOW) || (Child->Speed == EFI_USB_SPEED_FULL)) &&
      (Parent->Speed == EFI_USB_SPEED_HIGH)) {
    //
    // If the child is a low or full speed device, it is necessary to
    // set the transaction translator. Port TT is 1-based.
    // This is quite simple:
    //  1. if parent is of high speed, then parent is our translator
    //  2. otherwise use parent's translator.
    //
    Child->Translator.TranslatorHubAddress  = Parent->Address;
    Child->Translator.TranslatorPortNumber  = (UINT8) (Port + 1);
  } else {
    Child->Translator = Parent->Translator;
  }
//  DEBUG (( EFI_D_INFO, "UsbEnumerateNewDev: device uses translator (%d, %d)\n",
//           Child->Translator.TranslatorHubAddress,
//           Child->Translator.TranslatorPortNumber));
  DBG("UsbEnumerateNewDev: device uses translator (%d, %d)\n", Child->Translator.TranslatorHubAddress, Child->Translator.TranslatorPortNumber);
  //
  // After port is reset, hub establishes a signal path between
  // the device and host (DEFALUT state). Device's registers are
  // reset, use default address 0 (host enumerates one device at
  // a time) , and ready to respond to control transfer at EP 0.
  //

  //
  // Host assigns an address to the device. Device completes the
  // status stage with default address, then switches to new address.
  // ADDRESS state. Address zero is reserved for root hub.
  //
//  ASSERT (Bus->MaxDevices <= 256);
  for (Address = 1; Address < Bus->MaxDevices; Address++) {
    if (Bus->Devices[Address] == NULL) {
      break;
    }
  }

  if (Address >= Bus->MaxDevices) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: address pool is full for port %d\n", Port));
    DBG("UsbEnumerateNewDev: address pool is full for port %d\n", Port);
    Status = EFI_ACCESS_DENIED;
    goto ON_ERROR;
  }

  Status                = UsbSetAddress (Child, (UINT8)Address);
  Child->Address        = (UINT8)Address;
  Bus->Devices[Address] = Child;

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to set device address - %r\n", Status));
    goto ON_ERROR;
  }

  gBS->Stall (USB_SET_DEVICE_ADDRESS_STALL);

//  DEBUG ((EFI_D_INFO, "UsbEnumerateNewDev: device is now ADDRESSED at %d\n", Address));
  DBG("UsbEnumerateNewDev: device is now ADDRESSED at %d\n", Address);
  //
  // Host sends a Get_Descriptor request to learn the max packet
  // size of default pipe (only part of the device's descriptor).
  //
  Status = UsbGetMaxPacketSize0 (Child);

  if (EFI_ERROR (Status)) {
 //   DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to get max packet for EP 0 - %r\n", Status));
    DBG("UsbEnumerateNewDev: failed to get max packet for EP 0 - %r\n", Status);
    goto ON_ERROR;
  }

//  DEBUG (( EFI_D_INFO, "UsbEnumerateNewDev: max packet size for EP 0 is %d\n", Child->MaxPacket0));

  //
  // Host learns about the device's abilities by requesting device's
  // entire descriptions.
  //
  Status = UsbBuildDescTable (Child);

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to build descriptor table - %r\n", Status));
    DBG("UsbEnumerateNewDev: failed to build descriptor table - %r\n", Status);
    goto ON_ERROR;
  }

  //
  // Select a default configuration: UEFI must set the configuration
  // before the driver can connect to the device.
  //
  Config = Child->DevDesc->Configs[0]->Desc.ConfigurationValue;
  Status = UsbSetConfig (Child, Config);

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to set configure %d - %r\n", Config, Status));
    DBG("UsbEnumerateNewDev: failed to set configure %d - %r\n", Config, Status);
    goto ON_ERROR;
  }

 // DEBUG (( EFI_D_INFO, "UsbEnumerateNewDev: device %d is now in CONFIGED state\n", Address));
  DBG("UsbEnumerateNewDev: device %d is now in CONFIGED state\n", Address);
  //
  // Host assigns and loads a device driver.
  //
  Status = UsbSelectConfig (Child, Config);

  if (EFI_ERROR (Status)) {
//    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to create interfaces - %r\n", Status));
    DBG("UsbEnumerateNewDev: failed to create interfaces - %r\n", Status);
    goto ON_ERROR;
  }

  //
  // Report Status Code to indicate USB device has been detected by hotplug
  //
  REPORT_STATUS_CODE_WITH_DEVICE_PATH (
    EFI_PROGRESS_CODE,
    (EFI_IO_BUS_USB | EFI_IOB_PC_HOTPLUG),
    Bus->DevicePath
    );
  return EFI_SUCCESS;

ON_ERROR:
  //
  // If reach here, it means the enumeration process on a given port is interrupted due to error.
  // The s/w resources, including the assigned address(Address) and the allocated usb device data
  // structure(Bus->Devices[Address]), will NOT be freed here. These resources will be freed when
  // the device is unplugged from the port or DriverBindingStop() is invoked.
  //
  // This way is used to co-work with the lower layer EDKII UHCI/EHCI/XHCI host controller driver.
  // It's mainly because to keep UEFI spec unchanged EDKII XHCI driver have to maintain a state machine
  // to keep track of the mapping between actual address and request address. If the request address
  // (Address) is freed here, the Address value will be used by next enumerated device. Then EDKII XHCI
  // host controller driver will have wrong information, which will cause further transaction error.
  //
  // EDKII UHCI/EHCI doesn't get impacted as it's make sense to reserve s/w resource till it gets unplugged.
  //
/*
  if (Address != Bus->MaxDevices) {
    Bus->Devices[Address] = NULL;
  }

  if (Child != NULL) {
    UsbFreeDevice (Child);
  }
*/
  return Status;
}
Example #4
0
STATIC
EFI_STATUS
UsbEnumerateNewDev (
  IN USB_INTERFACE        *HubIf,
  IN UINT8                Port
  )
/*++

Routine Description:

  Enumerate and configure the new device on the port of this HUB interface.

Arguments:

  HubIf - The HUB that has the device connected
  Port  - The port index of the hub (started with zero)

Returns:

  EFI_SUCCESS          - The device is enumerated (added or removed)
  EFI_OUT_OF_RESOURCES - Failed to allocate resource for the device
  Others               - Failed to enumerate the device

--*/
{
  USB_BUS                 *Bus;
  USB_HUB_API             *HubApi;
  USB_DEVICE              *Child;
  USB_DEVICE              *Parent;
  EFI_USB_PORT_STATUS     PortState;
  UINT8                   Address;
  UINT8                   Config;
  EFI_STATUS              Status;

  Address = USB_MAX_DEVICES;
  Parent  = HubIf->Device;
  Bus     = Parent->Bus;
  HubApi  = HubIf->HubApi;
  
  gBS->Stall (USB_WAIT_PORT_STABLE_STALL);
  
  //
  // Hub resets the device for at least 10 milliseconds.
  // Host learns device speed. If device is of low/full speed
  // and the hub is a EHCI root hub, ResetPort will release
  // the device to its companion UHCI and return an error.
  //
  Status = HubApi->ResetPort (HubIf, Port);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to reset port %d - %r\n", Port, Status));

    return Status;
  }

  USB_DEBUG (("UsbEnumerateNewDev: hub port %d is reset\n", Port));

  Child = UsbCreateDevice (HubIf, Port);

  if (Child == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
  
  //
  // OK, now identify the device speed. After reset, hub
  // fully knows the actual device speed.
  //
  Status = HubApi->GetPortStatus (HubIf, Port, &PortState);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to get speed of port %d\n", Port));
    goto ON_ERROR;
  }

  if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_LOW_SPEED)) {
    Child->Speed = EFI_USB_SPEED_LOW;  

  } else if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_HIGH_SPEED)) {
    Child->Speed = EFI_USB_SPEED_HIGH; 

  } else {
    Child->Speed = EFI_USB_SPEED_FULL;
  }

  USB_DEBUG (("UsbEnumerateNewDev: device is of %d speed\n", Child->Speed));

  if (Child->Speed != EFI_USB_SPEED_HIGH) {
    //
    // If the child isn't a high speed device, it is necessary to
    // set the transaction translator. Port TT is 1-based.
    // This is quite simple:
    //  1. if parent is of high speed, then parent is our translator
    //  2. otherwise use parent's translator.
    //
    if (Parent->Speed == EFI_USB_SPEED_HIGH) {
      Child->Translator.TranslatorHubAddress  = Parent->Address;
      Child->Translator.TranslatorPortNumber  = Port + 1;

    } else {
      Child->Translator = Parent->Translator;
    }

    USB_DEBUG (("UsbEnumerateNewDev: device uses translator (%d, %d)\n", 
                Child->Translator.TranslatorHubAddress, 
                Child->Translator.TranslatorPortNumber));
  }
  
  //
  // After port is reset, hub establishes a signal path between
  // the device and host (DEFALUT state). Device¡¯s registers are
  // reset, use default address 0 (host enumerates one device at
  // a time) , and ready to respond to control transfer at EP 0.
  //
  
  //
  // Host sends a Get_Descriptor request to learn the max packet
  // size of default pipe (only part of the device¡¯s descriptor).
  //
  Status = UsbGetMaxPacketSize0 (Child);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to get max packet for EP 0 - %r\n", Status));
    goto ON_ERROR;
  }

  USB_DEBUG (("UsbEnumerateNewDev: max packet size for EP 0 is %d\n", Child->MaxPacket0));

  //
  // Host assigns an address to the device. Device completes the
  // status stage with default address, then switches to new address.
  // ADDRESS state. Address zero is reserved for root hub.
  //
  for (Address = 1; Address < USB_MAX_DEVICES; Address++) {
    if (Bus->Devices[Address] == NULL) {
      break;
    }
  }

  if (Address == USB_MAX_DEVICES) {
    USB_ERROR (("UsbEnumerateNewDev: address pool is full for port %d\n", Port));
    
    Status = EFI_ACCESS_DENIED;
    goto ON_ERROR;
  }

  Bus->Devices[Address] = Child;
  Status                = UsbSetAddress (Child, Address);
  Child->Address        = Address;
  
  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to set device address - %r\n", Status));
    goto ON_ERROR;
  }
  
  gBS->Stall (USB_SET_DEVICE_ADDRESS_STALL);

  USB_DEBUG (("UsbEnumerateNewDev: device is now ADDRESSED at %d\n", Address));

  //
  // Host learns about the device¡¯s abilities by requesting device's
  // entire descriptions.
  //
  Status = UsbBuildDescTable (Child);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to build descriptor table - %r\n", Status));
    goto ON_ERROR;
  }
  
  //
  // Select a default configuration: UEFI must set the configuration
  // before the driver can connect to the device.
  //
  Config = Child->DevDesc->Configs[0]->Desc.ConfigurationValue;
  Status = UsbSetConfig (Child, Config);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to set configure %d - %r\n", Config, Status));
    goto ON_ERROR;
  }

  USB_DEBUG (("UsbEnumerateNewDev: device %d is now in CONFIGED state\n", Address));
  
  //
  // Host assigns and loads a device driver. 
  //
  Status = UsbSelectConfig (Child, Config);

  if (EFI_ERROR (Status)) {
    USB_ERROR (("UsbEnumerateNewDev: failed to create interfaces - %r\n", Status));  
    goto ON_ERROR;
  }

  return EFI_SUCCESS;

ON_ERROR:
  if (Address != USB_MAX_DEVICES) {
    Bus->Devices[Address] = NULL;
  }

  if (Child != NULL) {
    UsbFreeDevice (Child);
  }

  return Status;
}