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  "identifier" : "/documentation/PCIDriverKit/tIOPCIAccessOptions",
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  "role" : "Enumeration",
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# tIOPCIAccessOptions

```
typedef enum tIOPCIAccessOptions : unsigned int { ... } tIOPCIAccessOptions;
```

## Overview

\abstract Options passed to memory space accessor functions

```
        and host software is permitted to offload the access to a DMA engine in order to free the CPU for other work to
        optimize overall system performance. Use of this hint may increase the latency of the memory space accessor function.
```

```
        if such a mapping is available. Care must be taken to ensure correct ordering of PCIe accesses (i.e., with memory barriers):
        1. Ordering between WC accesses to different addresses is not guaranteed.
        2. Ordering between WC and non-WC accesses is not guaranteed.
        3. To guarantee a write has been issued to the endpoint, a barrier is required.
```

## Topics

### Enumeration Cases

[`kIOPCIAccessLatencyTolerantHint`](/documentation/PCIDriverKit/tIOPCIAccessOptions/kIOPCIAccessLatencyTolerantHint)

[`kIOPCIAccessWriteCombining`](/documentation/PCIDriverKit/tIOPCIAccessOptions/kIOPCIAccessWriteCombining)

---

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