WdfDmaTransaction Execute: Any restriction on the object passed in 'Context' parameter (2. param)

NTDEV
1

Hi,

paging through the WDK examples, the WDL docu and Orwick/Smith, I don’t find it
very clear what type of parameters you can pass in the 2. parameter to
WdfDmaTransactionExecute.

The docu just says:
>>
Driver-defined context information. The framework passes the value specified for
Context, which can be a pointer, to the driver’s EvtProgramDma event callback
function. This parameter is optional and can be NULL.
>>

The examples (PLX, Nic) either show a null parameter ot the name of the callback
routine which is going to be called anyway (i.e. what is the real sense of the way
this is done in the NIC example)

Can I pass a pointer to a structure containing further info about the current
Transaction or is it better to do that in a transaction context set up when the
transaction is created (WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE etc.)?

I need to associate each transaction with an index pointing to the file (context
area) associated with the request.

2

There are no restrictions other than the context value needs to remain valid for the duration of the dma transfer. You can use whatever you want

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Charles
Sent: Monday, April 23, 2012 3:18 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] WdfDmaTransaction Execute: Any restriction on the object passed in ‘Context’ parameter (2. param)

Hi,

paging through the WDK examples, the WDL docu and Orwick/Smith, I don’t find it very clear what type of parameters you can pass in the 2. parameter to WdfDmaTransactionExecute.

The docu just says:
>>
Driver-defined context information. The framework passes the value specified for Context, which can be a pointer, to the driver’s EvtProgramDma event callback function. This parameter is optional and can be NULL.
>>

The examples (PLX, Nic) either show a null parameter ot the name of the callback routine which is going to be called anyway (i.e. what is the real sense of the way this is done in the NIC example)

Can I pass a pointer to a structure containing further info about the current Transaction or is it better to do that in a transaction context set up when the transaction is created (WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE etc.)?

I need to associate each transaction with an index pointing to the file (context
area) associated with the request.

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