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  "identifier" : "/documentation/SCSIControllerDriverKit/IOUserSCSIParallelInterfaceController/UserReportHBAConstraints",
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  "title" : "UserReportHBAConstraints"
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# UserReportHBAConstraints

Reports the I/O constraints for this controller.

```
virtual kern_return_t UserReportHBAConstraints(OSDictionary *constraints);
```

## Parameters

`constraints`

A dictionary containing I/O constraint keys, and Boolean values indicating that the device supports the constraint. See the discussion for valid and required keys.

## Return Value

A value that indicates the result of reporting the HBA constraints. <doc://com.apple.documentation/documentation/DriverKit/kIOReturnSuccess> indicates success. For error definitions, see <doc://com.apple.documentation/documentation/iokit/iokit_constants>.

## Discussion

The valid keys for the `constraints` dictionary are as follows:

|Key name                                                                                   |Required?|
|-------------------------------------------------------------------------------------------|---------|
|<doc://com.apple.documentation/documentation/iokit/kiomaximumsegmentcountreadkey>          |Yes      |
|<doc://com.apple.documentation/documentation/iokit/kiomaximumsegmentcountwritekey>         |Yes      |
|<doc://com.apple.documentation/documentation/iokit/kiomaximumsegmentbytecountreadkey>      |Yes      |
|<doc://com.apple.documentation/documentation/iokit/kiomaximumsegmentbytecountwritekey>     |Yes      |
|<doc://com.apple.documentation/documentation/iokit/kiominimumsegmentalignmentbytecountkey> |Yes      |
|<doc://com.apple.documentation/documentation/iokit/kiomaximumsegmentaddressablebitcountkey>|Yes      |
|`kIOMinimumHBADataAlignmentMaskKey`                                                        |Yes      |
|`kIOHierarchicalLogicalUnitSupportKey`                                                     |No       |

Subclasses must call this method from the dext before [`UserInitializeController`](/documentation/SCSIControllerDriverKit/IOUserSCSIParallelInterfaceController/UserInitializeController) returns.

---

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