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IOHIDDescriptorParser.h

Includes:

Overview

Functions

HIDCloseReportDescriptor: Disposes of the memory the parser allocated for the HIDOpenReportDescriptor function.
HIDGetButtonCapabilities: Returns the button capabilities structures for a HID device based on the given preparsed data.
HIDGetButtonCaps: Returns the button capabilities structures for a HID device based on the given preparsed data.
HIDGetButtons: The HIDGetButtons function takes a report from a HID device and gets the current state of the buttons in that report.
HIDGetButtonsOnPage: Retrieves the button stat information for buttons on a specified usage page.
HIDGetCapabilities: Returns the capabilities of a HID device based on the given preparsed data.
HIDGetCaps: Returns the capabilities of a HID device based on the given preparsed data.
HIDGetCollectionNodes: Returns an array of HIDCollectionNode structures that describe the relationships and layout of the link collections within this top level collection.
HIDGetScaledUsageValue: The HIDGetScaledUsageValue function returns the capabilities for all buttons for a given top level collection.
HIDGetSpecificButtonCapabilities: Retrieves the capabilities for all buttons in a specific type of report that meet the search criteria.
HIDGetSpecificButtonCaps: Retrieves the capabilities for all buttons in a specific type of report that meet the search criteria.
HIDGetSpecificValueCapabilities: Retrieves the capabilities for all values in a specific type of report that meet the search criteria.
HIDGetSpecificValueCaps: Retrieves the capabilities for all values in a specific type of report that meet the search criteria.
HIDGetUsageValue: The HIDGetUsageValue function returns a value from a device data report given a selected search criteria.
HIDGetUsageValueArray: The HIDGetUsageValueArray function returns a value from a device data report given a selected search criteria.
HIDGetValueCapabilities: The HIDGetValueCapabilities function retrieves the capabilities for all values for a specified top level collection.
HIDGetValueCaps: The HIDGetValueCaps function retrieves the capabilities for all values for a specified top level collection.
HIDMaxUsageListLength: The HIDMaxUsageListLength function returns the maximum number of buttons that can be returned from a given report type for the top level collection.
HIDOpenReportDescriptor: The HIDOpenReportDescriptor function allocates the memory the parser needs to handle the given report descriptor, and then parses the report descriptor.
HIDSetButton: The HIDSetButton function takes a report from a HID device and sets the current state of the specified button in that report.
HIDSetButtons: The HIDSetButtons function takes a report from a HID device and returns the current state of the buttons in that report.
HIDSetScaledUsageValue: The HIDSetScaledUsageValue function takes a signed physical (scaled) number and converts it to the logical, or device representation and inserts it in a given report.
HIDSetUsageValue: The HIDSetUsageValue function sets a value in a give report.
HIDSetUsageValueArray: The HIDSetUsageValueArray function sets an array of values in a given report.
HIDUsageListDifference: The HIDUsageListDifference function compares and provides the differences between two lists of buttons.

HIDCloseReportDescriptor

Disposes of the memory the parser allocated for the HIDOpenReportDescriptor function.

extern OSStatus HIDCloseReportDescriptor (
    HIDPreparsedDataRef preparsedDataRef);

Parameters

hidReportDescriptor: Contains a pointer to the actual HID report descriptor from the USB device's firmware
preparsedDataRef: Preparsed data reference for the report that is returned by the HIDOpenReportDescriptor function. After making a call to the HIDCloseReportDescriptor function, the preparsedDataRef is invalid and should not be used.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetButtonCapabilities

Returns the button capabilities structures for a HID device based on the given preparsed data.

extern OSStatus HIDGetButtonCapabilities (
    HIDReportType reportType, 
    HIDButtonCapabilitiesPtr buttonCaps, 
    UInt32 *buttonCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the scaled value. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport
buttonCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDButtonCapabilities structures. The structures contain information for all buttons that meet the search criteria
buttonCapsSize: Contains the size of the buttonCaps array passed in to the function and is set to the number of elements actually placed in the array after the call completes.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetButtonCaps

Returns the button capabilities structures for a HID device based on the given preparsed data.

extern OSStatus HIDGetButtonCaps (
    HIDReportType reportType, 
    HIDButtonCapsPtr buttonCaps, 
    UInt32 *buttonCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the scaled value. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport
buttonCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDButtonCaps structures. The structures contain information for all buttons that meet the search criteria
buttonCapsSize: Contains the size of the buttonCaps array passed in to the function and is set to the number of elements actually placed in the array after the call completes.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetButtons

The HIDGetButtons function takes a report from a HID device and gets the current state of the buttons in that report.

extern OSStatus HIDGetButtons (
    HIDReportType reportType, 
    UInt32 collection, 
    HIDUsageAndPagePtr usageList, 
    UInt32 *usageListSize, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report, provided in the report parameter, from which to retrieve the buttons. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport or kHIDFeatureReport
collection: Optionally specifies the link collection identifier used to retrieve only specific button states. If this value is non-zero, only the buttons that are part of the given collection are returned.
usageList: On return, points to a caller-allocated buffer that contains the usages of all the buttons that are pressed.
usageListSize: Is the size, in array elements, of the buffer provided in the usageList parameter. On return, this parameter contains the number of button states that were set by this routine. If the error kHIDBufferToSmallErr was returned, this parameter contains the number of array elements required to hold all button data requested. The maximum number of buttons that can ever be returned for a given type of report can be obtained by calling the HIDMaxUsageListLength function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the length, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetButtonsOnPage

Retrieves the button stat information for buttons on a specified usage page.

extern OSStatus HIDGetButtonsOnPage (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage *usageList, 
    UInt32 *usageListSize, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report, provided in the report parameter, from which to retrieve the buttons. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport or kHIDFeatureReport.
usagePage: Specifies the usage page of the buttons for which to retrieve the current state.
collection: Optionally specifies the link collection identifier used to retrieve only specific button states. If this value is non-zero, only the buttons that are part of the given collection are returned.
usageList: On return, points to a caller-allocated buffer that contains the usages of all the buttons that are perssed and belong to the usage page specified in the usagePage parameter.
usageListSize: Is the size, in array elements, of the buffer provided in the usageList parameter. On return, this parameter contains the number of button states that were set by this routine. If the error kHIDBufferTooSmallErr was returned, this parameter contains the number of array elements required to hold all button data requested. The maximum number of buttons that can ever be returned for a given type of report can be obtained by calling the HIDMaxUsageListLength function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetCapabilities

Returns the capabilities of a HID device based on the given preparsed data.

extern OSStatus HIDGetCapabilities (
    HIDPreparsedDataRef preparsedDataRef, 
    HIDCapabilitiesPtr capabilities);

Parameters

preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
capabilities: Points to a caller allocated buffer, that upon return contains the parsed capability information for this HID device.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetCaps

Returns the capabilities of a HID device based on the given preparsed data.

extern OSStatus HIDGetCaps (
    HIDPreparsedDataRef preparsedDataRef, 
    HIDCapsPtr capabilities);

Parameters

preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
capabilities: Points to a caller allocated buffer, that upon return contains the parsed capability information for this HID device.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDGetCollectionNodes

Returns an array of HIDCollectionNode structures that describe the relationships and layout of the link collections within this top level collection.

extern OSStatus HIDGetCollectionNodes (
    HIDCollectionNodePtr collectionNodes, 
    UInt32 *collectionNodesSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

collectionNodes: Points to a caller-allocated array of HIDCollectionNode structures in which this routine returns an entry for each collection within the top level collection. A collection is a group of corresponding HID descriptors containing input, output, and feature items that have some common relationship to one another. For example, a pointer collection contains items for x and y position data, and button data.
collectionNodesSize: On input, specifies the length in array elements of the buffer provided at collectionNodes. On output, this parameter is set to the number of entries in the collectionNodes array that were initialized.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The length of the buffer required, in array elements, for an entire collection node array is found in the HIDCaps structure member numberCollectionNodes. You obtain the HIDCaps information by calling the HIDGetCaps function. For information on the relationships of link collections described by the data returned from this routine, see the descripton of the HIDCollectionNode structure.

HIDGetScaledUsageValue

The HIDGetScaledUsageValue function returns the capabilities for all buttons for a given top level collection.

extern OSStatus HIDGetScaledUsageValue (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    SInt32 *usageValue, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report for which to retrieve the scaled value. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page of the value to be retrieved.
collection: Optionally specifies the link collection identifier of the value to be retrieved.
usage: Specifies the usage of the scaled value to be retrieved.
usageValue: Points to a variable, that on return from this routine holds the scaled value retrieved from the device report.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data
reportLength: Specifies the length, in bytes, of the report data provided at report

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

Clients who which to obtain all capabilities for a usage that contains multiple data items for a single usage that corresponds to a HID byte array, must call the HIDGetUsageValueArray function.

HIDGetSpecificButtonCapabilities

Retrieves the capabilities for all buttons in a specific type of report that meet the search criteria.

extern OSStatus HIDGetSpecificButtonCapabilities (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    HIDButtonCapabilitiesPtr buttonCaps, 
    UInt32 *buttonCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the button capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies a usage page identifier to use as a search criteria. If this parameter is non-zero, then only buttons that specify this usage page will be retrieved.
collection: Specifies a link collection identifier to use as a search criteria. If this parameter is non-zero, then only buttons that are part of the specified link collection are retrieved.
usage: Specifies a usage identifier to use as a search criteria. If this parameter is non-zero, then only buttons that match the value specified are retrieved.
buttonCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDButtonCapabilities structures. The structures contain information for all buttons that meet the search criteria.
buttonCapsLength: On input, specifies the length, in array elements, of the buffer provided in the buttonCaps parameter. On output, this parameter is set to the actual number of elements that were returned by the function call, in the buffer provided in the buttonCaps parameter, if the routine completed without error. The correct length necessary to retrieve the button capabilities can be found in the capability data returned for the device by the HIDGetCaps function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetSpecificButtonCapabilities function retrieves capability data for buttons that meet a given search criteria, as opposed to the HIDGetButtonCapabilities function which returns the capability data for all buttons on the device. Calling this routine specifying zero for usagePage, usage and collection is equivalent to calling the HIDGetButtonCapabilities function.

HIDGetSpecificButtonCaps

Retrieves the capabilities for all buttons in a specific type of report that meet the search criteria.

extern OSStatus HIDGetSpecificButtonCaps (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    HIDButtonCapsPtr buttonCaps, 
    UInt32 *buttonCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the button capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies a usage page identifier to use as a search criteria. If this parameter is non-zero, then only buttons that specify this usage page will be retrieved.
collection: Specifies a link collection identifier to use as a search criteria. If this parameter is non-zero, then only buttons that are part of the specified link collection are retrieved.
usage: Specifies a usage identifier to use as a search criteria. If this parameter is non-zero, then only buttons that match the value specified are retrieved.
buttonCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDButtonCaps structures. The structures contain information for all buttons that meet the search criteria.
buttonCapsLength: On input, specifies the length, in array elements, of the buffer provided in the buttonCaps parameter. On output, this parameter is set to the actual number of elements that were returned by the function call, in the buffer provided in the buttonCaps parameter, if the routine completed without error. The correct length necessary to retrieve the button capabilities can be found in the capability data returned for the device by the HIDGetCaps function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetSpecificButtonCaps function retrieves capability data for buttons that meet a given search criteria, as opposed to the HIDGetButtonCaps function which returns the capability data for all buttons on the device. Calling this routine specifying zero for usagePage, usage and collection is equivalent to calling the HIDGetButtonCaps function.

HIDGetSpecificValueCapabilities

Retrieves the capabilities for all values in a specific type of report that meet the search criteria.

extern OSStatus HIDGetSpecificValueCapabilities (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    HIDValueCapabilitiesPtr valueCaps, 
    UInt32 *valueCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the value capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport or kHIDFeatureReport.
usagePage: Specifies a usage page identifier to use as a search criteria. If this parameter is non-zero, then only values that specify this usage page will be retrieved.
collection: Specifies a link collection identifier to use as a search criteria. If this parameter is non-zero, then only values that are part of this link collection will be retrieved.
usage: Specifies a usage identifier to use as a search criteria. If this parameter is non-zero, then only values that specify this usage will be retrieved.
valueCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDValueCapabilities structures that contain information for all values that meet the search criteria.
valueCapsSize: Specifies the length on input, in array elements, of the buffer provided in the valueCaps parameter. On output, this parameter is set to the actual number of elements that were returned by this function call, in the buffer provided in the valueCaps parameter, if the routine completed without error. The correct length necessary to retrieve the value capabilities can be found in the capability data returned for the device from the HIDGetCaps function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetSpecificValueCapabilities function retrieves capability data for values that meet given search criteria, as opposed to the HIDGetValueCapabilities function, which returns the capability data for all values on the device. Calling this routine with a value of zero for usagePage, usage and collection parameters is equivalent to calling the HIDGetValueCapabilities function.

HIDGetSpecificValueCaps

Retrieves the capabilities for all values in a specific type of report that meet the search criteria.

extern OSStatus HIDGetSpecificValueCaps (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    HIDValueCapsPtr valueCaps, 
    UInt32 *valueCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the value capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport or kHIDFeatureReport.
usagePage: Specifies a usage page identifier to use as a search criteria. If this parameter is non-zero, then only values that specify this usage page will be retrieved.
collection: Specifies a link collection identifier to use as a search criteria. If this parameter is non-zero, then only values that are part of this link collection will be retrieved.
usage: Specifies a usage identifier to use as a search criteria. If this parameter is non-zero, then only values that specify this usage will be retrieved.
valueCaps: Points to a caller-allocated buffer that will contain, on return, an array of HIDValueCaps structures that contain information for all values that meet the search criteria.
valueCapsSize: Specifies the length on input, in array elements, of the buffer provided in the valueCaps parameter. On output, this parameter is set to the actual number of elements that were returned by this function call, in the buffer provided in the valueCaps parameter, if the routine completed without error. The correct length necessary to retrieve the value capabilities can be found in the capability data returned for the device from the HIDGetCaps function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetSpecificValueCaps function retrieves capability data for values that meet given search criteria, as opposed to the HIDGetValueCaps function, which returns the capability data for all values on the device. Calling this routine with a value of zero for usagePage, usage and collection parameters is equivalent to calling the HIDGetValueCaps function.

HIDGetUsageValue

The HIDGetUsageValue function returns a value from a device data report given a selected search criteria.

extern OSStatus HIDGetUsageValue (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    SInt32 *usageValue, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report, provided in report, from which to retrieve the value. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page of the value to retrieve.
collection: Optionally specifies the link collection identifier of the value to be retrieved.
usage: Specifies the usage of the value to be retrieved.
usageValue: Points to a variable, that on return from this routine holds the value retrieved from the device report.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetUsageValue function does not sign the value. To have the sign bit automatically applied, use the HIDGetScaledUsageValue function instead. For manually assigning the sign bit, the position of the sign bit can be found in the HIDValueCaps structure for this value. Clients who wish to obtain all data for a usage that contains multiple data items for a single usage, corresponding to a HID byte array, must call the HIDGetUsageValueArray function instead.

HIDGetUsageValueArray

The HIDGetUsageValueArray function returns a value from a device data report given a selected search criteria.

extern OSStatus HIDGetUsageValueArray (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    Byte *usageValueBuffer, 
    ByteCount usageValueBufferSize, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report, provided in report, from which to retrieve the value. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page of the data to be retrieved.
collection: Optionally specifies the link collection identifier of the data to be retrieved.
usage: Specifies the usage identifier of the value to be retrieved.
usageValueBuffer: Points to a caller-allocated buffer that contains, on output, the data from the device. The correct length for this buffer can be found by multiplying the reportCount and bitSize fields of the HIDValueCaps structure for the value and rounding the resulting value up to the nearest byte.
usageValueBufferSize: Specifies the size, in bytes, of the buffer in the usageValueBuffer parameter.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in report.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

When the HIDGetUsageValueArray function retrieves the data, it fills in the buffer in little-endian order beginning with the least significant bit of the data for this usage. The data is filled in without regard to byte alignment and is shifted such that the least significant bit is placed as the 1st bit of the given buffer.

HIDGetValueCapabilities

The HIDGetValueCapabilities function retrieves the capabilities for all values for a specified top level collection.

extern OSStatus HIDGetValueCapabilities (
    HIDReportType reportType, 
    HIDValueCapabilitiesPtr valueCaps, 
    UInt32 *valueCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the value capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
valueCaps: On return, points to a caller-allocated buffer that contains an array of HIDValueCapabilities structures containing information for all values in the top level collection.
valueCapsSize: On input, specifies the size in array elements of the buffer provided in the valueCaps parameter. On output, this parameter is set to the actual number of elements that were returned in the buffer provided in the valueCaps parameter, if the function completed without error. The correct length necessary to retrieve the value capabilities can be found in the capability data returned for the device by the HIDGetCapabilities function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetValueCapabilities function retrieves the capability data for all values in a top level collection without regard for the usage, usage page or collection of the value. To retrieve value capabilities for a specific usage, usage page or collection, use the HIDGetSpecificValueCapabilities function.

HIDGetValueCaps

The HIDGetValueCaps function retrieves the capabilities for all values for a specified top level collection.

extern OSStatus HIDGetValueCaps (
    HIDReportType reportType, 
    HIDValueCapsPtr valueCaps, 
    UInt32 *valueCapsSize, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to retrieve the value capabilities. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
valueCaps: On return, points to a caller-allocated buffer that contains an array of HIDValueCaps structures containing information for all values in the top level collection.
valueCapsSize: On input, specifies the size in array elements of the buffer provided in the valueCaps parameter. On output, this parameter is set to the actual number of elements that were returned in the buffer provided in the valueCaps parameter, if the function completed without error. The correct length necessary to retrieve the value capabilities can be found in the capability data returned for the device by the HIDGetCaps function.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDGetValueCaps function retrieves the capability data for all values in a top level collection without regard for the usage, usage page or collection of the value. To retrieve value capabilities for a specific usage, usage page or collection, use the HIDGetSpecificValueCaps function.

HIDMaxUsageListLength

The HIDMaxUsageListLength function returns the maximum number of buttons that can be returned from a given report type for the top level collection.

extern UInt32 HIDMaxUsageListLength (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    HIDPreparsedDataRef preparsedDataRef);

Parameters

reportType: Specifies the type of report for which to get a maximum usage count. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Optionally specifies the usage page identifier to use as a search criteria. If this parameter is zero, the function returns the number of buttons for the entire top-level collection regardless of the actual value of the usage page.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDOpenReportDescriptor

The HIDOpenReportDescriptor function allocates the memory the parser needs to handle the given report descriptor, and then parses the report descriptor.

extern OSStatus HIDOpenReportDescriptor (
    void *hidReportDescriptor, 
    ByteCount descriptorLength, 
    HIDPreparsedDataRef *preparsedDataRef, 
    UInt32 flags);

Parameters

hidReportDescriptor: Contains a pointer to the actual HID report descriptor from the USB device's firmware
descriptorLength: The length of the HID report descriptor
preparsedDataRef: Preparsed data reference to be used for subsequent function calls
flags: Flags for this runction are kHIDFlag_StrictErrorChecking = 0x00000001

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

When the parsed information is no longer needed, clients should call the HIDCloseReportDescriptor function.

HIDSetButton

The HIDSetButton function takes a report from a HID device and sets the current state of the specified button in that report.

extern OSStatus HIDSetButton (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page identifier of the value to be set in the report.
collection: Optionally specifies the link collection identifier to distinguish between buttons. If this parameter is zero, it is ignored.
usage: Points to a caller-allocated buffer that contains the button data to be set in the report in the report parameter.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDSetButtons

The HIDSetButtons function takes a report from a HID device and returns the current state of the buttons in that report.

extern OSStatus HIDSetButtons (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage *usageList, 
    UInt32 *usageListSize, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of repor. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page identifier of the value to be set in the report.
collection: Optionally specifies the link collection identifier to distinguish between buttons. If this parameter is zero, it is ignored.
usageList: Points to a caller-allocated buffer that contains an array of button data to be set in the report in the report parameter.
usageListSize: Specifies the size, in array elements, of the buffer provided in the usageList parameter. If an error is returned by a call to this function, the usageListLength parameter contains the location in the array provided in the usageList parameter where the error was encountered. All array entries encountered prior to the error location were successfully set in the report provided in the report parameter.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

HIDSetScaledUsageValue

The HIDSetScaledUsageValue function takes a signed physical (scaled) number and converts it to the logical, or device representation and inserts it in a given report.

extern OSStatus HIDSetScaledUsageValue (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    SInt32 usageValue, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page identifier of the value to be set in the report.
collection: Optionally specifies the link collection identifier to distinguish between values that have the same usage page and usage identifiers. If this parameter is zero, it will be ignored.
usage: Specifies the usage identifier of the value to be set in the report.
usageValue: Specifies the physical, or scaled, value to be set in the value for the given report.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
Specifies: the length, in bytes of the report data specified in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDSetScaledUsageValue function automatically handles the setting of the signed bit in the data to be sent to the device.

HIDSetUsageValue

The HIDSetUsageValue function sets a value in a give report.

extern OSStatus HIDSetUsageValue (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    SInt32 usageValue, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page identifier of the value to be set in the report.
collection: Optionally specifies the link collection identifier to distinguish between values that have the same usage page and usage identifiers. If this parameter is zero, it is ignored.
usage: Specifies the usage identifier of the value to be set in the report.
usageValue: Specifies the data that is to be set in the value for the given report.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDSetUsageVlaue function does not automatically handle the sign bit. Clients must either manually set the sign bit, at the position provided in the HIDValueCaps structure for this value, or call the HIDSetScaledUsageValue function.

HIDSetUsageValueArray

The HIDSetUsageValueArray function sets an array of values in a given report.

extern OSStatus HIDSetUsageValueArray (
    HIDReportType reportType, 
    HIDUsage usagePage, 
    UInt32 collection, 
    HIDUsage usage, 
    Byte *usageValueBuffer, 
    ByteCount usageValueBufferLength, 
    HIDPreparsedDataRef preparsedDataRef, 
    void *report, 
    ByteCount reportLength);

Parameters

reportType: Specifies the type of report. This parameter must be one of the following: kHIDInputReport, kHIDOutputReport, or kHIDFeatureReport.
usagePage: Specifies the usage page identifier of the value to be set in the report.
collection: Optionally specifies the link collection identifier to distinguish between values that have the same usage page and usage identifiers. If this parameter is zero, it is ignored.
usage: Specifies the usage identifier of the value to be set in the report.
usageValueBuffer: Points to a caller-allocated buffer that contains, on output, the data from the device. The correct length for this buffer can be found by multiplying the reportCount and bitSize fields of the HIDValueCaps structure for this value and rounding the resulting value up to the nearest byte.
usageValueBufferLength: Specifies the size, in bytes, of the buffer in the usageValueBuffer parameter.
preparsedDataRef: Preparsed data reference for the report that is retuned by the HIDOpenReportDescriptor function
report: Points to the caller-allocated buffer that contains the device report data.
reportLength: Specifies the size, in bytes, of the report data provided in the report parameter.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Discussion

The HIDSetUsageValue function does not automatically handle the sign bit. Clients must either manually set the sign bit, at the position provided in the HIDValueCaps structure for this value, or call the HIDSetScaledUsageValue function.

HIDUsageListDifference

The HIDUsageListDifference function compares and provides the differences between two lists of buttons.

extern OSStatus HIDUsageListDifference (
    HIDUsage *previousUsageList, 
    HIDUsage *currentUsageList, 
    HIDUsage *breakUsageList, 
    HIDUsage *makeUsageList, 
    UInt32 usageListsSize);

Parameters

previousUsageList: Points to the older button list to be used for comparison.
currentUsageList: Points to the newer button list to be used for comparison.
breakUsageList: On return, points to a caller-allocated buffer that contains the buttons set in the older list, specified in the previousUsageList parameter, but not set in the new list, specified in the currentUsageList parameter.
makeUsageList: On return, points to a caller-allocated buffer that contains the buttons set in the new list, specified in the currentUsageList parameter, but not set in the old list, specified in the previousUsageList parameter.
usageListsLength: Specifies the length, in array elements, of the buffers provided in the currentUsageList and previousUssageList parameters.

Return Value

OSStatus Returns an error code if an error was encountered or noErr on success.

Typedefs

HIDCaps

The HIDCaps data structure is used by HID clients to hold the capabilities of a HID device.

See Also:

HIDCaps

HIDCapsPtr

typedef struct HIDCaps HIDCaps, * HIDCapsPtr;

Fields

usage: Specifies the specific class of functionality that this device provides. This value is dependent and specific to the value provided in the usagePage field. For example, a keyboard could have a usagePage of kHIDUsagePage_Generic and a usage of kHIDUsage_Generic_Keyboard.
usagePage: Specifies the usage page identifier for this top level collection.
inputReportByteLength: Specifies the maximum length, in bytes, of an input report for this device, including the report ID which is unilaterally prepended to the device data.
outputReportByteLength: Specifies the maximum length, in bytes, of an output report for this device, including the report ID which is unilaterally prepended to the device data.
featureReportByteLength: Specifies the maximum length, in bytes, of a feature report for this device, including the report ID which is unilaterally prepended to the device data.
numberCollectionNodes: Specifies the number of HIDCollectionNode structures that are returned for this top level collection by the HIDGetConnectionNodes function.
numberInputButtonCaps: Specifies the number of input buttons.
numberInputValueCaps: Specifies the number of input values.
numberOutputButtonCaps: Specifies the number of output buttons.
numberOutputValueCaps: Specifies the number of output values
numberFeatureButtonCaps: Specifies the number of feature buttons.
numberFeatureValueCaps: Specifies the number of feature values.

Discussion

This structure holds the parsed capabilities and data maximums returned for a device by the HIDGetCaps function.

HIDCapsPtr

The HIDCaps data structure is used by HID clients to hold the capabilities of a HID device.

See Also:

HIDCaps

HIDCaps

typedef struct HIDCaps HIDCaps, * HIDCapsPtr;

Fields

usage: Specifies the specific class of functionality that this device provides. This value is dependent and specific to the value provided in the usagePage field. For example, a keyboard could have a usagePage of kHIDUsagePage_Generic and a usage of kHIDUsage_Generic_Keyboard.
usagePage: Specifies the usage page identifier for this top level collection.
inputReportByteLength: Specifies the maximum length, in bytes, of an input report for this device, including the report ID which is unilaterally prepended to the device data.
outputReportByteLength: Specifies the maximum length, in bytes, of an output report for this device, including the report ID which is unilaterally prepended to the device data.
featureReportByteLength: Specifies the maximum length, in bytes, of a feature report for this device, including the report ID which is unilaterally prepended to the device data.
numberCollectionNodes: Specifies the number of HIDCollectionNode structures that are returned for this top level collection by the HIDGetConnectionNodes function.
numberInputButtonCaps: Specifies the number of input buttons.
numberInputValueCaps: Specifies the number of input values.
numberOutputButtonCaps: Specifies the number of output buttons.
numberOutputValueCaps: Specifies the number of output values
numberFeatureButtonCaps: Specifies the number of feature buttons.
numberFeatureValueCaps: Specifies the number of feature values.

Discussion

This structure holds the parsed capabilities and data maximums returned for a device by the HIDGetCaps function.

HIDUsageAndPage

The HIDUsageAndPage data structure is used by HID clients when obtaining status of buttons to hold the usage page and usage of a button that is down.

See Also:

HIDUsageAndPage

HIDUsageAndPagePtr

typedef struct HIDUsageAndPage HIDUsageAndPage, *HIDUsageAndPagePtr;

Fields

usage: Specifies the usage identifier within the usage page specified by usagePage of a button that is down.
usagePage: Specifies the usage page identifier of a button that is down.

Discussion

Clients use the HIDUSageAndPage structure with the HIDGetButtonsEx function to obtain both the usage page and usage identifiers of each button that is down.

HIDUsageAndPagePtr

The HIDUsageAndPage data structure is used by HID clients when obtaining status of buttons to hold the usage page and usage of a button that is down.

See Also:

HIDUsageAndPage

HIDUsageAndPage

typedef struct HIDUsageAndPage HIDUsageAndPage, *HIDUsageAndPagePtr;

Fields

usage: Specifies the usage identifier within the usage page specified by usagePage of a button that is down.
usagePage: Specifies the usage page identifier of a button that is down.

Discussion

Clients use the HIDUSageAndPage structure with the HIDGetButtonsEx function to obtain both the usage page and usage identifiers of each button that is down.

Structs and Unions

HIDCaps

The HIDCaps data structure is used by HID clients to hold the capabilities of a HID device.

See Also:

HIDCaps

HIDCapsPtr

struct HIDCaps { 
    HIDUsage usage; 
    HIDUsage usagePage; 
    ByteCount inputReportByteLength; 
    ByteCount outputReportByteLength; 
    ByteCount featureReportByteLength; 
    UInt32 numberCollectionNodes; 
    UInt32 numberInputButtonCaps; 
    UInt32 numberInputValueCaps; 
    UInt32 numberOutputButtonCaps; 
    UInt32 numberOutputValueCaps; 
    UInt32 numberFeatureButtonCaps; 
    UInt32 numberFeatureValueCaps; 
};

Fields

usage: Specifies the specific class of functionality that this device provides. This value is dependent and specific to the value provided in the usagePage field. For example, a keyboard could have a usagePage of kHIDUsagePage_Generic and a usage of kHIDUsage_Generic_Keyboard.
usagePage: Specifies the usage page identifier for this top level collection.
inputReportByteLength: Specifies the maximum length, in bytes, of an input report for this device, including the report ID which is unilaterally prepended to the device data.
outputReportByteLength: Specifies the maximum length, in bytes, of an output report for this device, including the report ID which is unilaterally prepended to the device data.
featureReportByteLength: Specifies the maximum length, in bytes, of a feature report for this device, including the report ID which is unilaterally prepended to the device data.
numberCollectionNodes: Specifies the number of HIDCollectionNode structures that are returned for this top level collection by the HIDGetConnectionNodes function.
numberInputButtonCaps: Specifies the number of input buttons.
numberInputValueCaps: Specifies the number of input values.
numberOutputButtonCaps: Specifies the number of output buttons.
numberOutputValueCaps: Specifies the number of output values
numberFeatureButtonCaps: Specifies the number of feature buttons.
numberFeatureValueCaps: Specifies the number of feature values.

Discussion

This structure holds the parsed capabilities and data maximums returned for a device by the HIDGetCaps function.

HIDUsageAndPage

The HIDUsageAndPage data structure is used by HID clients when obtaining status of buttons to hold the usage page and usage of a button that is down.

See Also:

HIDUsageAndPage

HIDUsageAndPagePtr

struct HIDUsageAndPage { 
    HIDUsage usage; 
    HIDUsage usagePage; 
};

Fields

usage: Specifies the usage identifier within the usage page specified by usagePage of a button that is down.
usagePage: Specifies the usage page identifier of a button that is down.

Discussion

Clients use the HIDUSageAndPage structure with the HIDGetButtonsEx function to obtain both the usage page and usage identifiers of each button that is down.

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Last Updated: 2008-12-19