author | Graeme Price <GRAEME.PRICE@NOKIA.COM> |
Fri, 15 Oct 2010 14:32:18 +0100 | |
changeset 15 | 307f4279f433 |
permissions | -rw-r--r-- |
15
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
1 |
<?xml version="1.0" encoding="utf-8"?> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
2 |
<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
3 |
<!-- This component and the accompanying materials are made available under the terms of the License |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
4 |
"Eclipse Public License v1.0" which accompanies this distribution, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
5 |
and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
6 |
<!-- Initial Contributors: |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
7 |
Nokia Corporation - initial contribution. |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
8 |
Contributors: |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
9 |
--> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
10 |
<!DOCTYPE concept |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
11 |
PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
12 |
<concept id="GUID-6AC01B10-92C1-4E56-813B-6853DFCF3386-GENID-1-2-1-9-1-6-1-8-1-7-1-5-1" xml:lang="en"><title>DMA Requests</title><shortdesc>Describes how device drivers use DMA requests to initiate |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
13 |
a DMA transfer.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
14 |
<p>DMA transfer requests are the way in which a device driver sets |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
15 |
up and initiates a DMA transfer. A transfer request internally comprises |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
16 |
a linked list of DMA descriptor headers and is associated with a single |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
17 |
DMA channel. A transfer request also stores an optional client-provided |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
18 |
callback function, which can be invoked when the whole request completes, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
19 |
whether successfully or not. A DMA request can be in any of the four |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
20 |
states: Not configured, Idle, Being transferred, and Pending. However, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
21 |
these states are not used by the driver. </p> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
22 |
<p>A device driver creates a DMA request by specifying a DMA channel |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
23 |
and an optional DMA callback function to be called after the request |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
24 |
completion. A DMA request must be fragmented. </p> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
25 |
<p>The following shows the creation of a DMA request: </p> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
26 |
<codeblock id="GUID-B2753DE7-800E-57CC-B2B6-CA2548AC25C4-GENID-1-2-1-9-1-6-1-8-1-7-1-5-1-3-4" xml:space="preserve">TInt DExDriverUartTxDma::Init() |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
27 |
{ |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
28 |
... |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
29 |
// A DMA request has to be created for any DMA transfer. This |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
30 |
// specifies the channel on which the DMA request shall be |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
31 |
// made, the service callback function to be called after the |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
32 |
// request completion (TxDmaService), and an object pointer that will be passed |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
33 |
// as an argument to DMA request service function (this). |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
34 |
// A DMA request is a list of fragments small enough to be |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
35 |
// transferred in one go by the DMA Controller. |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
36 |
// |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
37 |
iTxDmaRequest = new DDmaRequest(*iTxDmaChannel, TxDmaService, this); |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
38 |
if(iTxDmaRequest == NULL) |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
39 |
{ |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
40 |
return KErrNoMemory; |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
41 |
} |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
42 |
... |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
43 |
}</codeblock> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
44 |
</conbody></concept> |