---
title: UserReportMediumBlockSize
framework: scsiperipheralsdriverkit
role: symbol
role_heading: Instance Method
platforms: [driverkit 22.0+]
path: scsiperipheralsdriverkit/iouserscsiperipheraldevicetype05/userreportmediumblocksize
---

# UserReportMediumBlockSize

Provides a report on the external device’s block size.

## Declaration

```occ
virtual kern_return_t UserReportMediumBlockSize(UInt64 *blockSize);
```

## Parameters

- `blockSize`: On return, the external device’s block size.

## Return Value

Return Value A value that indicates the result of the report request. kIOReturnSuccess indicates success. For error definitions, see IOKit Constants.

## Discussion

Discussion This call populates blockSize with the granularity of the block size, such as 512 bytes or 4096 bytes (4 KB).