---
title: minphys
framework: Kernel
role: symbol
role_heading: Function
platforms: [macOS 10.4+]
path: kernel/1561824-minphys
---

# minphys

Adjust a buffer's count to be no more than maximum physical I/O transfer size for the host architecture.

## Declaration

```occ
u_int minphys(buf_t bp);
```

## Parameters

- `bp`: The buffer whose byte count to modify.

## Return Value

Return Value New byte count.

## Discussion

Discussion physio() takes as a parameter a function to bound transfer sizes for each VNOP_STRATEGY() call. minphys() is a default implementation. It calls buf_setcount() to make the buffer's count the min() of its current count and the max I/O size for the host architecture.