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Configuration Descriptor Parser
USB Descriptors

USB Configuration Descriptor definitions. More...

## Macros
#define | DESCRIPTOR_CAST(DescriptorPtr, Type) (*DESCRIPTOR_PCAST(DescriptorPtr, Type))
#define | DESCRIPTOR_PCAST(DescriptorPtr, Type) ((Type*)(DescriptorPtr))
#define | DESCRIPTOR_SIZE(DescriptorPtr) DESCRIPTOR_PCAST(DescriptorPtr, USB_Descriptor_Header_t)->Size
#define | DESCRIPTOR_TYPE(DescriptorPtr) DESCRIPTOR_PCAST(DescriptorPtr, USB_Descriptor_Header_t)->Type

## Typedefs
typedef uint8_t(* | ConfigComparatorPtr_t )(void *)

## Enumerations
enum | DSearch_Comp_Return_ErrorCodes_t { DESCRIPTOR_SEARCH_COMP_Found = 0, DESCRIPTOR_SEARCH_COMP_Fail = 1, DESCRIPTOR_SEARCH_COMP_EndOfDescriptor = 2 }
enum | DSearch_Return_ErrorCodes_t { DESCRIPTOR_SEARCH_Found = 0, DESCRIPTOR_SEARCH_Fail = 1, DESCRIPTOR_SEARCH_NotFound = 2 }
enum | USB_Host_GetConfigDescriptor_ErrorCodes_t { HOST_GETCONFIG_Successful = 0, HOST_GETCONFIG_DeviceDisconnect = 1, HOST_GETCONFIG_PipeError = 2, HOST_GETCONFIG_SetupStalled = 3, HOST_GETCONFIG_SoftwareTimeOut = 4, HOST_GETCONFIG_BuffOverflow = 5, HOST_GETCONFIG_InvalidData = 6 }

## Functions
static void | USB_GetNextDescriptor (uint16_t *const BytesRem, void **CurrConfigLoc) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2)
uint8_t | USB_GetNextDescriptorComp (uint16_t *const BytesRem, void **const CurrConfigLoc, ConfigComparatorPtr_t const ComparatorRoutine) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2) ATTR_NON_NULL_PTR_ARG(3)
void | USB_GetNextDescriptorOfType (uint16_t *const BytesRem, void **const CurrConfigLoc, const uint8_t Type) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2)
void | USB_GetNextDescriptorOfTypeAfter (uint16_t *const BytesRem, void **const CurrConfigLoc, const uint8_t Type, const uint8_t AfterType) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2)
void | USB_GetNextDescriptorOfTypeBefore (uint16_t *const BytesRem, void **const CurrConfigLoc, const uint8_t Type, const uint8_t BeforeType) ATTR_NON_NULL_PTR_ARG(1) ATTR_NON_NULL_PTR_ARG(2)
uint8_t | USB_Host_GetDeviceConfigDescriptor (const uint8_t ConfigNumber, uint16_t *const ConfigSizePtr, void *const BufferPtr, const uint16_t BufferSize) ATTR_NON_NULL_PTR_ARG(2) ATTR_NON_NULL_PTR_ARG(3)

## Detailed Description

This section of the library gives a friendly API which can be used in host applications to easily parse an attached device's configuration descriptor so that endpoint, interface and other descriptor data can be extracted and used as needed.

## Macro Definition Documentation

#define DESCRIPTOR_CAST | ( |  | DescriptorPtr,
|  |  | Type
| ) |  | (*DESCRIPTOR_PCAST(DescriptorPtr, Type))

Casts a pointer to a descriptor inside the configuration descriptor into the given descriptor type (as an actual struct instance rather than a pointer to a struct).

Usage Example:

uint8_t* CurrDescriptor = &ConfigDescriptor[0]; // Pointing to the configuration header
USB_Descriptor_Configuration_Header_t ConfigHeader = DESCRIPTOR_CAST(CurrDescriptor,
USB_Descriptor_Configuration_Header_t);
// Can now access elements of the configuration header struct using the . operator

#define DESCRIPTOR_PCAST | ( |  | DescriptorPtr,
|  |  | Type
| ) |  | ((Type*)(DescriptorPtr))

Casts a pointer to a descriptor inside the configuration descriptor into a pointer to the given descriptor type.

Usage Example:

uint8_t* CurrDescriptor = &ConfigDescriptor[0]; // Pointing to the configuration header
USB_Descriptor_Configuration_Header_t* ConfigHeaderPtr = DESCRIPTOR_PCAST(CurrDescriptor,
USB_Descriptor_Configuration_Header_t);
// Can now access elements of the configuration header struct using the -> indirection operator

#define DESCRIPTOR_SIZE | ( |  | DescriptorPtr | ) | DESCRIPTOR_PCAST(DescriptorPtr, USB_Descriptor_Header_t)->Size

Returns the descriptor's size, expressed as the 8-bit value indicating the number of bytes.

#define DESCRIPTOR_TYPE | ( |  | DescriptorPtr | ) | DESCRIPTOR_PCAST(DescriptorPtr, USB_Descriptor_Header_t)->Type

Returns the descriptor's type, expressed as the 8-bit type value in the header of the descriptor. This value's meaning depends on the descriptor's placement in the descriptor, but standard type values can be accessed in the USB_DescriptorTypes_t enum.

## Typedef Documentation

typedef uint8_t(* ConfigComparatorPtr_t)(void *)

Type define for a Configuration Descriptor comparator function (function taking a pointer to an array of type void, returning a uint8_t value).

See also
  USB_GetNextDescriptorComp function for more details.

## Enumeration Type Documentation

enum DSearch_Comp_Return_ErrorCodes_t

Enum for return values of USB_GetNextDescriptorComp().

Enumerator
DESCRIPTOR_SEARCH_COMP_Found | Configuration descriptor now points to descriptor which matches search criteria of the given comparator function.
DESCRIPTOR_SEARCH_COMP_Fail | Comparator function returned DESCRIPTOR_SEARCH_Fail.
DESCRIPTOR_SEARCH_COMP_EndOfDescriptor | End of configuration descriptor reached before match found.

enum DSearch_Return_ErrorCodes_t

Enum for return values of a descriptor comparator function.

Enumerator
DESCRIPTOR_SEARCH_Found | Current descriptor matches comparator criteria.
DESCRIPTOR_SEARCH_Fail | No further descriptor could possibly match criteria, fail the search.
DESCRIPTOR_SEARCH_NotFound | Current descriptor does not match comparator criteria.

enum USB_Host_GetConfigDescriptor_ErrorCodes_t

Enum for the possible return codes of the USB_Host_GetDeviceConfigDescriptor() function.

Enumerator
HOST_GETCONFIG_Successful | No error occurred while retrieving the configuration descriptor.
HOST_GETCONFIG_DeviceDisconnect | The attached device was disconnected while retrieving the configuration descriptor.
HOST_GETCONFIG_PipeError | An error occurred in the pipe while sending the request.
HOST_GETCONFIG_SetupStalled | The attached device stalled the request to retrieve the configuration descriptor.
HOST_GETCONFIG_SoftwareTimeOut | The request or data transfer timed out.
HOST_GETCONFIG_BuffOverflow | The device's configuration descriptor is too large to fit into the allocated buffer.
HOST_GETCONFIG_InvalidData | The device returned invalid configuration descriptor data.

## Function Documentation

static void USB_GetNextDescriptor | ( | uint16_t *const | BytesRem,
|  | void ** | CurrConfigLoc
| ) |  |
| inline static

Skips over the current sub-descriptor inside the configuration descriptor, so that the pointer then points to the next sub-descriptor. The bytes remaining value is automatically decremented.

Parameters

  [in,out] | BytesRem | Pointer to the number of bytes remaining of the configuration descriptor.
  [in,out] | CurrConfigLoc | Pointer to the current descriptor inside the configuration descriptor.

uint8_t USB_GetNextDescriptorComp | ( | uint16_t *const | BytesRem,
|  | void **const | CurrConfigLoc,
|  | ConfigComparatorPtr_t const | ComparatorRoutine
| ) |  |

Searches for the next descriptor in the given configuration descriptor using a pre-made comparator function. The routine updates the position and remaining configuration descriptor bytes values automatically. If a comparator routine fails a search, the descriptor pointer is retreated back so that the next descriptor search invocation will start from the descriptor which first caused the original search to fail. This behavior allows for one comparator to be used immediately after another has failed, starting the second search from the descriptor which failed the first.

Comparator functions should be standard functions which accept a pointer to the header of the current descriptor inside the configuration descriptor which is being compared, and should return a value from the DSearch_Return_ErrorCodes_t enum as a uint8_t value.

Note
  This function is available in USB Host mode only.

Parameters

  [in,out] | BytesRem | Pointer to an int storing the remaining bytes in the configuration descriptor.
  [in,out] | CurrConfigLoc | Pointer to the current position in the configuration descriptor.
  [in] | ComparatorRoutine | Name of the comparator search function to use on the configuration descriptor.

Returns
  Value of one of the members of the DSearch_Comp_Return_ErrorCodes_t enum.

Usage Example:

uint8_t EndpointSearcher(void* CurrentDescriptor); // Comparator Prototype
uint8_t EndpointSearcher(void* CurrentDescriptor)
{
if (DESCRIPTOR_TYPE(CurrentDescriptor) == DTYPE_Endpoint)
return DESCRIPTOR_SEARCH_Found;
else
return DESCRIPTOR_SEARCH_NotFound;
}
//...
// After retrieving configuration descriptor:
if (USB_Host_GetNextDescriptorComp(&BytesRemaining, &CurrentConfigLoc, EndpointSearcher) ==
Descriptor_Search_Comp_Found)
{
// Do something with the endpoint descriptor
}

void USB_GetNextDescriptorOfType | ( | uint16_t *const | BytesRem,
|  | void **const | CurrConfigLoc,
|  | const uint8_t | Type
| ) |  |

Skips to the next sub-descriptor inside the configuration descriptor of the specified type value. The bytes remaining value is automatically decremented.

Parameters

  [in,out] | BytesRem | Pointer to the number of bytes remaining of the configuration descriptor.
  [in,out] | CurrConfigLoc | Pointer to the current descriptor inside the configuration descriptor.
  [in] | Type | Descriptor type value to search for.

void USB_GetNextDescriptorOfTypeAfter | ( | uint16_t *const | BytesRem,
|  | void **const | CurrConfigLoc,
|  | const uint8_t | Type,
|  | const uint8_t | AfterType
| ) |  |

Skips to the next sub-descriptor inside the configuration descriptor of the specified type value, which must come after a descriptor of the second given type value. The bytes remaining value is automatically decremented.

Parameters

  [in,out] | BytesRem | Pointer to the number of bytes remaining of the configuration descriptor.
  [in,out] | CurrConfigLoc | Pointer to the current descriptor inside the configuration descriptor.
  [in] | Type | Descriptor type value to search for.
  [in] | AfterType | Descriptor type value which must be reached before the given Type descriptor.

void USB_GetNextDescriptorOfTypeBefore | ( | uint16_t *const | BytesRem,
|  | void **const | CurrConfigLoc,
|  | const uint8_t | Type,
|  | const uint8_t | BeforeType
| ) |  |

Skips to the next sub-descriptor inside the configuration descriptor of the specified type value, which must come before a descriptor of the second given type value. If the BeforeType type descriptor is reached first, the number of bytes remaining to process is set to zero and the function exits. The bytes remaining value is automatically decremented.

Parameters

  [in,out] | BytesRem | Pointer to the number of bytes remaining of the configuration descriptor.
  [in,out] | CurrConfigLoc | Pointer to the current descriptor inside the configuration descriptor.
  [in] | Type | Descriptor type value to search for.
  [in] | BeforeType | Descriptor type value which must not be reached before the given Type descriptor.

uint8_t USB_Host_GetDeviceConfigDescriptor | ( | const uint8_t | ConfigNumber,
|  | uint16_t *const | ConfigSizePtr,
|  | void *const | BufferPtr,
|  | const uint16_t | BufferSize
| ) |  |

Retrieves the configuration descriptor data from an attached device via a standard request into a buffer, including validity and size checking to prevent a buffer overflow.

Parameters

  [in] | ConfigNumber | Device configuration descriptor number to fetch from the device (usually set to 1 for single configuration devices).
  [in,out] | ConfigSizePtr | Pointer to a location for storing the retrieved configuration descriptor size.
  [out] | BufferPtr | Pointer to the buffer for storing the configuration descriptor data.
  [out] | BufferSize | Size of the allocated buffer where the configuration descriptor is to be stored.

Returns
  A value from the USB_Host_GetConfigDescriptor_ErrorCodes_t enum.