USBD_SelectConfigUrbAllocateAndBuild routine

The USBD_SelectConfigUrbAllocateAndBuild routine allocates and formats a URB structure that is required to select a configuration for a USB device.

Note  In Windows 8, USBD_SelectConfigUrbAllocateAndBuild replaces USBD_CreateConfigurationRequestEx and USBD_CreateConfigurationRequest.

Syntax

NTSTATUS USBD_SelectConfigUrbAllocateAndBuild(
  _In_   USBD_HANDLE USBDHandle,
  _In_   PUSB_CONFIGURATION_DESCRIPTOR ConfigurationDescriptor,
  _In_   PUSBD_INTERFACE_LIST_ENTRY InterfaceList,
  _Out_  PURB *Urb
);

Parameters

USBDHandle [in]

USBD handle that is retrieved by the client driver in a previous call to the USBD_CreateHandle routine.

ConfigurationDescriptor [in]

Pointer to a caller-allocated USB_CONFIGURATION_DESCRIPTOR structure that contains the configuration descriptor for the configuration to be selected. Typically, the client driver submits an URB of the type URB_FUNCTION_GET_DESCRIPTOR_FROM_DEVICE (see _URB_CONTROL_DESCRIPTOR_REQUEST) to retrieve information about configurations, interfaces, endpoints, the vendor, and class-specific descriptors from a USB device. When the client driver specifies USB_CONFIGURATION_DESCRIPTOR_TYPE as the descriptor type, the request retrieves all device information in a USB_CONFIGURATION_DESCRIPTOR structure. The driver then passes the received pointer to the USB_CONFIGURATION_DESCRIPTOR structure in the ConfigurationDescriptor parameter.

InterfaceList [in]

Pointer to the first element of a caller-allocated array of USBD_INTERFACE_LIST_ENTRY structures. The length of the array depends on the number of interfaces in the configuration descriptor. For more information, see Remarks.

Urb [out]

Pointer to a URB structure that receives the URB allocated by USBD_SelectConfigUrbAllocateAndBuild. The client driver must free the URB when the driver has finished using it by calling USBD_UrbFree.

Return value

The USBD_SelectConfigUrbAllocateAndBuild routine returns an NT status code.

Possible values include, but are not limited to, the status codes listed in the following table.

Remarks

Before calling USBD_SelectConfigUrbAllocateAndBuild, the client driver must perform the following tasks:

1. Get the number of interfaces in the configuration. This information is contained in the bNumInterfaces member of the USB_CONFIGURATION_DESCRIPTOR structure pointed to by ConfigurationDescriptor.
2. Create an array of USBD_INTERFACE_LIST_ENTRY structures. The number of elements in the array must be one more than the number of interfaces. Initialize the array by calling RtlZeroMemory.
3. Obtain an interface descriptor for each interface (or its alternate setting) in the configuration. You can obtain those interface descriptors by calling USBD_ParseConfigurationDescriptorEx.
4. For each element (except the last element) in the array, set the InterfaceDescriptor member to the address of an interface descriptor. For the first element in the array, set the InterfaceDescriptor member to the address of the interface descriptor that represents the first interface in the configuration. Similarly for the nth element in the array, set the InterfaceDescriptor member to the address of the interface descriptor that represents the nth interface in the configuration.
5. The InterfaceDescriptor member of the last element must be set to NULL.

USBD_SelectConfigUrbAllocateAndBuild performs the following tasks:

• Creates an URB and fills it with information about the specified configuration, its interfaces and endpoints, and sets the request type to URB_FUNCTION_SELECT_CONFIGURATION.
• Fills a USBD_INTERFACE_INFORMATION structure in the URB for each interface.
• Sets the Interface member of the nth element of the caller-provided USBD_INTERFACE_LIST_ENTRY array to the address of the corresponding USBD_INTERFACE_INFORMATION structure in the URB.

You can use the received pointer to the URB structure to submit a select-configuration request to the USB driver stack to set the specified configuration. In addition, you can use the Interface member of each USBD_INTERFACE_INFORMATION structure in the array to get information about the interface. Within each USBD_INTERFACE_INFORMATION structure, the Pipes member is an array of USBD_PIPE_INFORMATION structures. Each USBD_PIPE_INFORMATION structure contains information about the pipes opened (by the USB driver stack) for the endpoints in that interface. You can obtain pipe handles from the array and store them for future I/O requests to the device.

Requirements

See also

USBD_CreateHandle

USBD_CreateConfigurationRequestEx

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Build date: 12/5/2013