NdisAllocateBufferPool

NdisAllocateBufferPool

VOID
   NdisAllocateBufferPool(
       OUT PNDIS_STATUS Status,
       OUT PNDIS_HANDLE PoolHandle,
       IN UINT NumberOfDescriptors
       );

NdisAllocateBufferPool returns a handle with which the caller can allocate buffer descriptors by calling NdisAllocateBuffer.

Parameters

Status

Points to a caller-supplied variable in which this function returns the final status of the buffer pool allocation, which is always NDIS_STATUS_SUCCESS.

PoolHandle

Points to a caller-supplied variable in which this function returns a handle to the buffer pool. This handle is a required parameter to the Ndis..Buffer functions that the driver calls subsequently.

NumberOfDescriptors

Specifies the number of buffer descriptors the caller expects to allocate from the buffer pool without releasing any allocated buffer descriptors back to the pool.

Comments

After NdisAllocateBufferPool returns, the driver calls NdisAllocateBuffer one or more times to allocate the buffer descriptors that it requires. A driver should call NdisAllocateBufferPool during initialization.

The NumberOfDescriptors specified by a NIC driver usually depends on the features of the NIC. For example, the driver of a busmaster DMA NIC with ring buffers would specify at least a large enough NumberOfDescriptors to map the full ring.

The NumberOfDescriptors specified in the call to NdisAllocateBufferPool is the effective limit on how many times the driver can call NdisAllocateBuffer before it must call NdisFreeBuffer to return a buffer descriptor to the free list for the buffer pool.

When a driver no longer needs the buffer pool it allocated, it calls NdisFreeBufferPool to release the buffer pool handle.

The driver must release any spin lock it is holding before calling NdisAllocateBufferPool.

All lower-level NDIS drivers must allocate all buffer descriptors that they chain to packets from buffer pool. Only highest-level protocol drivers can be given OS-dependent descriptors mapping virtual memory ranges, and, if these memory descriptors are equivalent to NDIS buffer descriptors, a highest-level protocol can pass such descriptors as parameters to NdisXxx functions.

Callers of NdisAllocateBufferPool run at IRQL <= DISPATCH_LEVEL.