author | Graeme Price <GRAEME.PRICE@NOKIA.COM> |
Fri, 15 Oct 2010 14:32:18 +0100 | |
changeset 15 | 307f4279f433 |
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307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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<?xml version="1.0" encoding="utf-8"?> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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<!-- 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:
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<!-- 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:
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"Eclipse Public License v1.0" which accompanies this distribution, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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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:
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<!-- Initial Contributors: |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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Nokia Corporation - initial contribution. |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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Contributors: |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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--> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
changeset
|
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<!DOCTYPE concept |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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<concept id="GUID-EBF4F1F1-F76B-455B-B8EE-B7965CF0717E" xml:lang="en"><title>The LDD/PDD |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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Model</title><shortdesc>This document describes how device drivers are implemented as logical |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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device drivers (LDDs) and physical device drivers (PDDs).</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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<section id="GUID-4549DF88-EEB0-4CF2-BC93-A234E3ED553F"> <p>Device |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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driver DLLs come in two types - the logical device driver (LDD), and the physical |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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device driver (PDD). Typically, a single LDD supports functionality common |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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to a class of hardware devices, whereas a PDD supports a specific member of |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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that class. This means that the generic code in the LDD only needs to be written |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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once, and the same user-side API can be used for all variants of a device. </p> <p>Many |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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PDDs may be associated with a single LDD. For example, there is a single serial |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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communications LDD (<filepath>ECOMM.LDD</filepath>) which is used with all |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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UARTs. This LDD provides buffering and flow control functions that are required |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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|
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with all types of UART. On a particular hardware platform, this LDD will be |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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accompanied by one or more PDDs, which support the different types of UART |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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present. A single PDD can support more than one UART of the same type; separate |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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PDDs are only required for UARTs with different programming interfaces. Typically, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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the PDD is kept as small as possible. </p> <p>Only LDDs communicate with user-side |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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code; PDDs communicate only with the corresponding LDD, with the variant or |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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kernel extensions, and with the hardware itself. Device drivers provide their |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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interface for user side applications by implementing a class derived from |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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the Kernel API <xref href="GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066.dita"><apiname>RBusLogicalChannel</apiname></xref>. The functions of the |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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derived class form a thin layer over the functions defined in <codeph>RBusLogicalChannel</codeph> and |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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are commonly implemented inline and published in a header file. However, if |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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the API functions need to do more complex tasks, then they can be implemented |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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in their own DLL. The kernel also provides a API <xref href="GUID-92BAC78E-8ACF-3952-8E77-CCF93ED3BDC9.dita"><apiname>RDevice</apiname></xref>, |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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which enables user side code to get information about a device. </p> <p>The |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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following diagram shows the general idea: </p><fig id="GUID-CB291406-75EC-572E-8A21-280A5F0A6B9E"> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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<title> Device driver LDD/PDD model </title> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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<image href="GUID-6EB38F10-849D-5763-96A0-A0A108982D67_d0e63496_href.png" placement="inline"/> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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</fig><p>To make porting to particular hardware platforms easier, some drivers |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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|
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make a further logical split in their PDD code between a platform-independent |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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layer (PIL), which contains code that is common to all the hardware platforms |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
44 |
that the driver could be deployed on, and a platform-specific layer (PSL), |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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which contains code such as the reading and writing of hardware-specific registers. </p> <p>Depending |
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Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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|
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on the device or the type of device to access, this split between LDD and |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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PDD may not be necessary; the device driver may simply consist of an LDD alone. </p> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
diff
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|
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</section> |
307f4279f433
Initial contribution of the Adaptation Documentation.
Graeme Price <GRAEME.PRICE@NOKIA.COM>
parents:
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</conbody></concept> |