Commit 84d77833 authored by Dean Camera's avatar Dean Camera
Browse files

Remove ConfigDescriptor.c/.h files from the ClassDriver Host demos, as they...

Remove ConfigDescriptor.c/.h files from the ClassDriver Host demos, as they will be obsoleted when the Host mode class drivers are complete. Add new StillImage stub class driver common header.
parent 345506b1
/*
LUFA Library
Copyright (C) Dean Camera, 2009.
dean [at] fourwalledcubicle [dot] com
www.fourwalledcubicle.com
*/
/*
Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness. In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.
*/
/** \file
*
* USB Device Configuration Descriptor processing routines, to determine the correct pipe configurations
* needed to communication with an attached USB device. Descriptors are special computer-readable structures
* which the host requests upon device enumeration, to determine the device's capabilities and functions.
*/
#include "ConfigDescriptor.h"
/** Reads and processes an attached device's descriptors, to determine compatibility and pipe configurations. This
* routine will read in the entire configuration descriptor, and configure the hosts pipes to correctly communicate
* with compatible devices.
*
* This routine searches for a CDC interface descriptor containing bulk data IN and OUT endpoints, and an interrupt event endpoint.
*
* \return An error code from the CDCHost_GetConfigDescriptorDataCodes_t enum.
*/
uint8_t ProcessConfigurationDescriptor(void)
{
uint8_t* ConfigDescriptorData;
uint16_t ConfigDescriptorSize;
uint8_t FoundEndpoints = 0;
/* Get Configuration Descriptor size from the device */
if (USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, NULL) != HOST_SENDCONTROL_Successful)
return ControlError;
/* Ensure that the Configuration Descriptor isn't too large */
if (ConfigDescriptorSize > MAX_CONFIG_DESCRIPTOR_SIZE)
return DescriptorTooLarge;
/* Allocate enough memory for the entire config descriptor */
ConfigDescriptorData = alloca(ConfigDescriptorSize);
/* Retrieve the entire configuration descriptor into the allocated buffer */
USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, ConfigDescriptorData);
/* Validate returned data - ensure first entry is a configuration header descriptor */
if (DESCRIPTOR_TYPE(ConfigDescriptorData) != DTYPE_Configuration)
return InvalidConfigDataReturned;
/* Get the CDC control interface from the configuration descriptor */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextCDCControlInterface) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Descriptor not found, error out */
return NoCDCInterfaceFound;
}
/* Get the IN and OUT data endpoints for the CDC interface */
while (FoundEndpoints != ((1 << CDC_NOTIFICATIONPIPE) | (1 << CDC_DATAPIPE_IN) | (1 << CDC_DATAPIPE_OUT)))
{
/* Fetch the next bulk or interrupt endpoint from the current CDC interface */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextInterfaceCDCDataEndpoint) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Check to see if the control interface's notification pipe has been found, if so search for the data interface */
if (FoundEndpoints & (1 << CDC_NOTIFICATIONPIPE))
{
/* Get the next CDC data interface from the configuration descriptor (CDC class has two CDC interfaces) */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextCDCDataInterface) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Descriptor not found, error out */
return NoCDCInterfaceFound;
}
}
else
{
/* Clear the found endpoints mask, since any already processed endpoints aren't in the CDC interface we need */
FoundEndpoints = 0;
/* Disable any already configured pipes from the invalid CDC interfaces */
Pipe_SelectPipe(CDC_NOTIFICATIONPIPE);
Pipe_DisablePipe();
Pipe_SelectPipe(CDC_DATAPIPE_IN);
Pipe_DisablePipe();
Pipe_SelectPipe(CDC_DATAPIPE_OUT);
Pipe_DisablePipe();
/* Get the next CDC control interface from the configuration descriptor (CDC class has two CDC interfaces) */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextCDCControlInterface) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Descriptor not found, error out */
return NoCDCInterfaceFound;
}
}
/* Fetch the next bulk or interrupt endpoint from the current CDC interface */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextInterfaceCDCDataEndpoint) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Descriptor not found, error out */
return NoEndpointFound;
}
}
USB_Descriptor_Endpoint_t* EndpointData = DESCRIPTOR_PCAST(ConfigDescriptorData, USB_Descriptor_Endpoint_t);
/* Check if the found endpoint is a interrupt or bulk type descriptor */
if ((EndpointData->Attributes & EP_TYPE_MASK) == EP_TYPE_INTERRUPT)
{
/* If the endpoint is a IN type interrupt endpoint */
if (EndpointData->EndpointAddress & ENDPOINT_DESCRIPTOR_DIR_IN)
{
/* Configure the notification pipe */
Pipe_ConfigurePipe(CDC_NOTIFICATIONPIPE, EP_TYPE_INTERRUPT, PIPE_TOKEN_IN,
EndpointData->EndpointAddress, EndpointData->EndpointSize, PIPE_BANK_SINGLE);
Pipe_SetInfiniteINRequests();
Pipe_SetInterruptPeriod(EndpointData->PollingIntervalMS);
/* Set the flag indicating that the notification pipe has been found */
FoundEndpoints |= (1 << CDC_NOTIFICATIONPIPE);
}
}
else
{
/* Check if the endpoint is a bulk IN or bulk OUT endpoint */
if (EndpointData->EndpointAddress & ENDPOINT_DESCRIPTOR_DIR_IN)
{
/* Configure the data IN pipe */
Pipe_ConfigurePipe(CDC_DATAPIPE_IN, EP_TYPE_BULK, PIPE_TOKEN_IN,
EndpointData->EndpointAddress, EndpointData->EndpointSize, PIPE_BANK_SINGLE);
Pipe_SetInfiniteINRequests();
Pipe_Unfreeze();
/* Set the flag indicating that the data IN pipe has been found */
FoundEndpoints |= (1 << CDC_DATAPIPE_IN);
}
else
{
/* Configure the data OUT pipe */
Pipe_ConfigurePipe(CDC_DATAPIPE_OUT, EP_TYPE_BULK, PIPE_TOKEN_OUT,
EndpointData->EndpointAddress, EndpointData->EndpointSize, PIPE_BANK_SINGLE);
Pipe_Unfreeze();
/* Set the flag indicating that the data OUT pipe has been found */
FoundEndpoints |= (1 << CDC_DATAPIPE_OUT);
}
}
}
/* Valid data found, return success */
return SuccessfulConfigRead;
}
/** Descriptor comparator function. This comparator function is can be called while processing an attached USB device's
* configuration descriptor, to search for a specific sub descriptor. It can also be used to abort the configuration
* descriptor processing if an incompatible descriptor configuration is found.
*
* This comparator searches for the next Interface descriptor of the correct CDC control Class, Subclass and Protocol values.
*
* \return A value from the DSEARCH_Return_ErrorCodes_t enum
*/
uint8_t DComp_NextCDCControlInterface(void* CurrentDescriptor)
{
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Interface)
{
/* Check the CDC descriptor class, subclass and protocol, break out if correct control interface found */
if ((DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).Class == CDC_CONTROL_CLASS) &&
(DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).SubClass == CDC_CONTROL_SUBCLASS) &&
(DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).Protocol == CDC_CONTROL_PROTOCOL))
{
return DESCRIPTOR_SEARCH_Found;
}
}
return DESCRIPTOR_SEARCH_NotFound;
}
/** Descriptor comparator function. This comparator function is can be called while processing an attached USB device's
* configuration descriptor, to search for a specific sub descriptor. It can also be used to abort the configuration
* descriptor processing if an incompatible descriptor configuration is found.
*
* This comparator searches for the next Interface descriptor of the correct CDC data Class, Subclass and Protocol values.
*
* \return A value from the DSEARCH_Return_ErrorCodes_t enum
*/
uint8_t DComp_NextCDCDataInterface(void* CurrentDescriptor)
{
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Interface)
{
/* Check the CDC descriptor class, subclass and protocol, break out if correct data interface found */
if ((DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).Class == CDC_DATA_CLASS) &&
(DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).SubClass == CDC_DATA_SUBCLASS) &&
(DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).Protocol == CDC_DATA_PROTOCOL))
{
return DESCRIPTOR_SEARCH_Found;
}
}
return DESCRIPTOR_SEARCH_NotFound;
}
/** Descriptor comparator function. This comparator function is can be called while processing an attached USB device's
* configuration descriptor, to search for a specific sub descriptor. It can also be used to abort the configuration
* descriptor processing if an incompatible descriptor configuration is found.
*
* This comparator searches for the next bulk IN or OUT endpoint, or interrupt IN endpoint within the current interface,
* aborting the search if another interface descriptor is found before the required endpoint (so that it may be compared
* using a different comparator to determine if it is another CDC class interface).
*
* \return A value from the DSEARCH_Return_ErrorCodes_t enum
*/
uint8_t DComp_NextInterfaceCDCDataEndpoint(void* CurrentDescriptor)
{
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Endpoint)
{
uint8_t EndpointType = (DESCRIPTOR_CAST(CurrentDescriptor,
USB_Descriptor_Endpoint_t).Attributes & EP_TYPE_MASK);
if ((EndpointType == EP_TYPE_BULK) || (EndpointType == EP_TYPE_INTERRUPT))
return DESCRIPTOR_SEARCH_Found;
}
else if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Interface)
{
return DESCRIPTOR_SEARCH_Fail;
}
return DESCRIPTOR_SEARCH_NotFound;
}
/*
LUFA Library
Copyright (C) Dean Camera, 2009.
dean [at] fourwalledcubicle [dot] com
www.fourwalledcubicle.com
*/
/*
Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness. In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.
*/
/** \file
*
* Header file for ConfigDescriptor.c.
*/
#ifndef _CONFIGDESCRIPTOR_H_
#define _CONFIGDESCRIPTOR_H_
/* Includes: */
#include <LUFA/Drivers/USB/USB.h> // USB Functionality
#include "CDCHost.h"
/* Macros: */
/** Interface Class value for the CDC class */
#define CDC_CONTROL_CLASS 0x02
/** Interface Class value for the CDC Communication Interface subclass */
#define CDC_CONTROL_SUBCLASS 0x02
/** Interface Class value for the CDC protocol */
#define CDC_CONTROL_PROTOCOL 0x01
/** Interface Class value for the CDC data class */
#define CDC_DATA_CLASS 0x0A
/** Interface Class value for the CDC data subclass (unused) */
#define CDC_DATA_SUBCLASS 0x00
/** Interface Class value for the CDC data protocol */
#define CDC_DATA_PROTOCOL 0x00
/** Maximum size of a device configuration descriptor which can be processed by the host, in bytes */
#define MAX_CONFIG_DESCRIPTOR_SIZE 512
/* Enums: */
/** Enum for the possible return codes of the ProcessConfigurationDescriptor() function. */
enum CDCHost_GetConfigDescriptorDataCodes_t
{
SuccessfulConfigRead = 0, /**< Configuration Descriptor was processed successfully */
ControlError = 1, /**< A control request to the device failed to complete successfully */
DescriptorTooLarge = 2, /**< The device's Configuration Descriptor is too large to process */
InvalidConfigDataReturned = 3, /**< The device returned an invalid Configuration Descriptor */
NoCDCInterfaceFound = 4, /**< A compatible CDC interface was not found in the device's Configuration Descriptor */
NoEndpointFound = 5, /**< Compatible CDC endpoints were not found in the device's CDC interface */
};
/* Function Prototypes: */
uint8_t ProcessConfigurationDescriptor(void);
uint8_t DComp_NextCDCControlInterface(void* CurrentDescriptor);
uint8_t DComp_NextCDCDataInterface(void* CurrentDescriptor);
uint8_t DComp_NextInterfaceCDCDataEndpoint(void* CurrentDescriptor);
#endif
/*
LUFA Library
Copyright (C) Dean Camera, 2009.
dean [at] fourwalledcubicle [dot] com
www.fourwalledcubicle.com
*/
/*
Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness. In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.
*/
/** \file
*
* USB Device Configuration Descriptor processing routines, to determine the correct pipe configurations
* needed to communication with an attached USB device. Descriptors are special computer-readable structures
* which the host requests upon device enumeration, to determine the device's capabilities and functions.
*/
#include "ConfigDescriptor.h"
/** Reads and processes an attached device's descriptors, to determine compatibility and pipe configurations. This
* routine will read in the entire configuration descriptor, and configure the hosts pipes to correctly communicate
* with compatible devices.
*
* This routine searches for a HID interface descriptor containing at least one Interrupt type IN endpoint.
*
* \return An error code from the GenericHIDHost_GetConfigDescriptorDataCodes_t enum.
*/
uint8_t ProcessConfigurationDescriptor(void)
{
uint8_t* ConfigDescriptorData;
uint16_t ConfigDescriptorSize;
uint8_t FoundEndpoints = 0;
/* Get Configuration Descriptor size from the device */
if (USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, NULL) != HOST_SENDCONTROL_Successful)
return ControlError;
/* Ensure that the Configuration Descriptor isn't too large */
if (ConfigDescriptorSize > MAX_CONFIG_DESCRIPTOR_SIZE)
return DescriptorTooLarge;
/* Allocate enough memory for the entire config descriptor */
ConfigDescriptorData = alloca(ConfigDescriptorSize);
/* Retrieve the entire configuration descriptor into the allocated buffer */
USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, ConfigDescriptorData);
/* Validate returned data - ensure first entry is a configuration header descriptor */
if (DESCRIPTOR_TYPE(ConfigDescriptorData) != DTYPE_Configuration)
return InvalidConfigDataReturned;
/* Get the HID interface from the configuration descriptor */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextHIDInterface) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Descriptor not found, error out */
return NoHIDInterfaceFound;
}
while (FoundEndpoints != ((1 << HID_DATA_IN_PIPE) | (1 << HID_DATA_OUT_PIPE)))
{
/* Get the next HID interface's data endpoint descriptor */
if (USB_GetNextDescriptorComp(&ConfigDescriptorSize, &ConfigDescriptorData,
DComp_NextInterfaceHIDDataEndpoint) != DESCRIPTOR_SEARCH_COMP_Found)
{
/* Not all HID devices have an OUT endpoint - if we've reached the end of the HID descriptor
* but only found the mandatory IN endpoint, it's safe to continue with the device enumeration */
if (FoundEndpoints == (1 << HID_DATA_IN_PIPE))
break;
/* Descriptor not found, error out */
return NoEndpointFound;
}
/* Retrieve the endpoint address from the endpoint descriptor */
USB_Descriptor_Endpoint_t* EndpointData = DESCRIPTOR_PCAST(ConfigDescriptorData, USB_Descriptor_Endpoint_t);
/* If the endpoint is a IN type endpoint */
if (EndpointData->EndpointAddress & ENDPOINT_DESCRIPTOR_DIR_IN)
{
/* Configure the HID data IN pipe */
Pipe_ConfigurePipe(HID_DATA_IN_PIPE, EP_TYPE_INTERRUPT, PIPE_TOKEN_IN,
EndpointData->EndpointAddress, EndpointData->EndpointSize, PIPE_BANK_SINGLE);
Pipe_SetInfiniteINRequests();
FoundEndpoints |= (1 << HID_DATA_IN_PIPE);
}
else
{
/* Configure the HID data OUT pipe */
Pipe_ConfigurePipe(HID_DATA_OUT_PIPE, EP_TYPE_INTERRUPT, PIPE_TOKEN_OUT,
EndpointData->EndpointAddress, EndpointData->EndpointSize, PIPE_BANK_SINGLE);
FoundEndpoints |= (1 << HID_DATA_OUT_PIPE);
}
}
/* Valid data found, return success */
return SuccessfulConfigRead;
}
/** Descriptor comparator function. This comparator function is can be called while processing an attached USB device's
* configuration descriptor, to search for a specific sub descriptor. It can also be used to abort the configuration
* descriptor processing if an incompatible descriptor configuration is found.
*
* This comparator searches for the next Interface descriptor of the correct HID Class value.
*
* \return A value from the DSEARCH_Return_ErrorCodes_t enum
*/
uint8_t DComp_NextHIDInterface(void* CurrentDescriptor)
{
/* Determine if the current descriptor is an interface descriptor */
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Interface)
{
/* Check the HID descriptor class and protocol, break out if correct class/protocol interface found */
if (DESCRIPTOR_CAST(CurrentDescriptor, USB_Descriptor_Interface_t).Class == HID_CLASS)
{
/* Indicate that the descriptor being searched for has been found */
return DESCRIPTOR_SEARCH_Found;
}
}
/* Current descriptor does not match what this comparator is looking for */
return DESCRIPTOR_SEARCH_NotFound;
}
/** Descriptor comparator function. This comparator function is can be called while processing an attached USB device's
* configuration descriptor, to search for a specific sub descriptor. It can also be used to abort the configuration
* descriptor processing if an incompatible descriptor configuration is found.
*
* This comparator searches for the next Endpoint descriptor inside the current interface descriptor,
* aborting the search if another interface descriptor is found before the required endpoint.
*
* \return A value from the DSEARCH_Return_ErrorCodes_t enum
*/
uint8_t DComp_NextInterfaceHIDDataEndpoint(void* CurrentDescriptor)
{
/* Determine the type of the current descriptor */
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Endpoint)
{
/* Indicate that the descriptor being searched for has been found */
return DESCRIPTOR_SEARCH_Found;
}
else if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Interface)
{
/* Indicate that the search has failed prematurely and should be aborted */
return DESCRIPTOR_SEARCH_Fail;
}
/* Current descriptor does not match what this comparator is looking for */
return DESCRIPTOR_SEARCH_NotFound;
}
......@@ -46,11 +46,10 @@
#include <LUFA/Version.h>
#include <LUFA/Drivers/Misc/TerminalCodes.h>
#include <LUFA/Drivers/USB/USB.h>
#include <LUFA/Drivers/Peripheral/SerialStream.h>
#include <LUFA/Drivers/Board/LEDs.h>
#include "ConfigDescriptor.h"
#include <LUFA/Drivers/USB/USB.h>
#include <LUFA/Drivers/USB/Class/HID.h>
/* Macros: */
/** Pipe number for the HID data IN pipe */
......
......@@ -124,7 +124,6 @@ LUFA_PATH = ../../../..
# List C source files here. (C dependencies are automatically generated.)
SRC = $(TARGET).c \
ConfigDescriptor.c \
$(LUFA_PATH)/LUFA/Drivers/Peripheral/SerialStream.c \
$(LUFA_PATH)/LUFA/Drivers/Peripheral/Serial.c \
$(LUFA_PATH)/LUFA/Drivers/USB/LowLevel/DevChapter9.c \
......
/*
LUFA Library
Copyright (C) Dean Camera, 2009.
dean [at] fourwalledcubicle [dot] com
www.fourwalledcubicle.com
*/
/*
Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness. In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.
*/
/** \file
*
* USB Device Configuration Descriptor processing routines, to determine the correct pipe configurations
* needed to communication with an attached USB device. Descriptors are special computer-readable structures
* which the host requests upon device enumeration, to determine the device's capabilities and functions.
*/
#include "ConfigDescriptor.h"
/** Reads and processes an attached device's descriptors, to determine compatibility and pipe configurations. This
* routine will read in the entire configuration descriptor, and configure the hosts pipes to correctly communicate
* with compatible devices.
*
* This routine searches for a HID interface descriptor containing at least one Interrupt type IN endpoint.
*
* \return An error code from the KeyboardHost_GetConfigDescriptorDataCodes_t enum.
*/
uint8_t ProcessConfigurationDescriptor(void)
{
uint8_t* ConfigDescriptorData;
uint16_t ConfigDescriptorSize;
/* Get Configuration Descriptor size from the device */
if (USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, NULL) != HOST_SENDCONTROL_Successful)
return ControlError;
/* Ensure that the Configuration Descriptor isn't too large */
if (ConfigDescriptorSize > MAX_CONFIG_DESCRIPTOR_SIZE)
return DescriptorTooLarge;
/* Allocate enough memory for the entire config descriptor */
ConfigDescriptorData = alloca(ConfigDescriptorSize);
/* Retrieve the entire configuration descriptor into the allocated buffer */
USB_GetDeviceConfigDescriptor(&ConfigDescriptorSize, ConfigDescriptorData);