|
1 <?xml version="1.0" encoding="utf-8"?> |
|
2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
|
3 <!-- This component and the accompanying materials are made available under the terms of the License |
|
4 "Eclipse Public License v1.0" which accompanies this distribution, |
|
5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
|
6 <!-- Initial Contributors: |
|
7 Nokia Corporation - initial contribution. |
|
8 Contributors: |
|
9 --> |
|
10 <!DOCTYPE concept |
|
11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
|
12 <concept id="GUID-ADB848FD-317A-521C-9684-BBCF20358207" xml:lang="en"><title>Architecture</title><shortdesc>Describes the USB client architecture.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
|
13 <p>Symbian platform provides access to USB client hardware through its USB |
|
14 client driver. </p> |
|
15 <p>The following diagram shows the USB client architecture. Devices can provide |
|
16 more than one USB function. To better show the typical use, the diagram shows |
|
17 the components in use with a phone that is configured as a combined |
|
18 WHCM and OBEX peripheral. </p> |
|
19 <fig id="GUID-8627CEA3-B570-5DA0-AE30-32C9AE08F041"> |
|
20 <image href="GUID-365283F1-54B4-519A-81EC-9B5018896DDE_d0e35432_href.png" placement="inline"/> |
|
21 </fig> |
|
22 <p>There are three main elements: </p> |
|
23 <ul> |
|
24 <li id="GUID-95956004-F78F-53E5-A2F3-693B48D344E8"><p>The user side interface |
|
25 to the USB client driver. </p> </li> |
|
26 <li id="GUID-6461280C-469F-5726-AE69-9A88ADCC95AB"><p>The USB client driver |
|
27 LDD that provides the driver's logical channel. This is hardware independent. </p> </li> |
|
28 <li id="GUID-FD47D854-620E-5E2A-9A59-79B4901477D2"><p>The PDD, or client controller, |
|
29 that manages access to the USB client hardware. </p> </li> |
|
30 </ul> |
|
31 <section id="GUID-57BF46A0-0FE2-4074-87DF-A0C55AA29F1F"><title>User API</title> <p>The user side interface to the USB client |
|
32 driver is provided by <xref href="GUID-B1E32178-3B7C-3B00-A0AF-62ECE40E8598.dita"><apiname>RDevUsbcClient</apiname></xref>. The user side interface |
|
33 is implemented as a set of inline functions and means that there is no separate |
|
34 user side library component. This is typically the case for device drivers. </p> </section> |
|
35 <section id="GUID-2C341305-95E0-53C4-B4D5-1BB03CCB8C52"><title>USB client |
|
36 driver (LDD)</title> <p>The USB client driver provides an interface to the |
|
37 USB client device. The USB client driver is also referred to as a <i>channel</i> to |
|
38 the USB client device; it may also be referred to as the USB logical device |
|
39 driver. </p> <p>Each user component that requires a connection to the USB |
|
40 client device opens a channel using the user side <xref href="GUID-B1E32178-3B7C-3B00-A0AF-62ECE40E8598.dita"><apiname>RDevUsbcClient</apiname></xref> class. </p> <p>A |
|
41 channel supports only one USB interface. A channel (i.e. the USB LDD) can |
|
42 be loaded as many times as needed; the decision is based on the number of |
|
43 interfaces required. This can be done either in the same process or in a different |
|
44 process depending on the relationship between the interfaces. </p> <p>If there |
|
45 is more than one channel open on the USB client device, then they can all |
|
46 share Control Endpoint 0 (Ep0). Each channel can make a request on this endpoint. |
|
47 The other endpoints cannot be shared between channels; instead each endpoint |
|
48 is used exclusively by one, and only one, channel. </p> <p>Each channel can |
|
49 claim up to a maximum of <i>five</i> endpoints in addition to Ep0. Each endpoint |
|
50 claimed on a channel is locally numbered from one and five. This number need |
|
51 not correspond to the actual endpoint number of the hardware interface; this |
|
52 number is called the logical endpoint number, and all transfer requests use |
|
53 the logical number for the endpoint. A driver can, however, discover the physical |
|
54 endpoint address of a logical endpoint by requesting the endpoint descriptor. </p> <p>A |
|
55 channel can have asynchronous requests outstanding on one or more of its endpoints |
|
56 simultaneously; this includes Ep0. As Ep0 can be shared between channels, |
|
57 then the underlying USB Controller must manage multiple requests on this endpoint </p> </section> |
|
58 <section id="GUID-660CC1A9-26B5-5869-ADC9-53196AF5F387"><title>USB client |
|
59 controller (PDD)</title> <p>The USB client controller manages access to the |
|
60 USB client hardware on behalf of all USB client drivers. It has a two layer |
|
61 implementation: </p> <ul> |
|
62 <li id="GUID-A90C62D9-60B0-5542-9D93-683A7C02EDB2"><p>a licensee product independent |
|
63 layer that provides an API for the USB client driver. This is often referred |
|
64 to as the Platform Independent Layer, and forms the 'upper' part of the USB |
|
65 physical device driver (PDD). </p> </li> |
|
66 <li id="GUID-4637A61F-A1D7-522A-B824-4603AF129442"><p>a layer that interfaces |
|
67 with the hardware. This is often referred to as the Platform Specific Layer, |
|
68 and forms the 'lower' part of the USB physical device driver (PDD). <i>It |
|
69 is this part that needs porting effort</i>. </p> </li> |
|
70 </ul> <p>The Platform Independent Layer contains, as far as possible, the |
|
71 functionality that is defined in the USB specification. This includes the |
|
72 ‘Chapter 9’ device state handling and request processing. The Platform Specific |
|
73 Layer contains only that functionality which cannot be abstracted and made |
|
74 generic, because different USB Device Controller designs are programmed differently |
|
75 and operate differently. </p> <p>The complete USB client controller (PDD) |
|
76 is an instance of a <xref href="GUID-82FA9C04-0B7E-3FAD-9AAD-3A68E1E6A941.dita"><apiname>DUsbClientController</apiname></xref> derived class |
|
77 and is implemented as a kernel extension named <filepath>usbcc.dll</filepath>. </p> <p>The |
|
78 functionality of the Platform Independent Layer is provided by the base class <xref href="GUID-82FA9C04-0B7E-3FAD-9AAD-3A68E1E6A941.dita"><apiname>DUsbClientController</apiname></xref>. |
|
79 This class also defines a large number of pure virtual functions that are |
|
80 intended to provide the functionality that is not part of the USB specification, |
|
81 but is specific to the USB Device Controller. Such functions typically implement |
|
82 direct USB Device Controller hardware manipulation, register access, endpoint |
|
83 FIFO loading/unloading etc. The platform specific layer provides the implementation |
|
84 for these pure virtual functions by defining and implementing a device specific |
|
85 class derived from <codeph>DUsbClientController</codeph>. </p> </section> |
|
86 </conbody></concept> |