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<concept id="GUID-4E3C086B-25BE-4DAC-9E21-CFC4F8B792A5" xml:lang="en"><title>DMA

Technology Guide</title><shortdesc>Describes the new Direct Memory Access framework.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-E987EF55-27CE-4EC2-B250-2C3D7C36CAF9"><title>Purpose</title><p>The

Symbian platform DMA framework provides a generic simple interface for the

clients to access DMA resources in a device. The primary clients are device

drivers that will use the DMA framework to set up DMA transfers.</p></section>

<section id="GUID-7607CC80-0FA0-4FC2-897A-C4AB6B6C74FC"><title>Key concepts</title><fig id="GUID-93B0F1CF-5F84-4952-8D8C-7BE581EC5353">

<title>New DMA Framework</title>

<image href="GUID-74C99E44-8900-47FB-AF79-5627C37B9843_d0e325662_href.png" placement="inline"/>

</fig><dl>

<dlentry>

<dt>DMA Client</dt>

<dd><p>A device driver or other kernel objects that needs to use the resources

of the DMA framework.</p></dd>

</dlentry>

<dlentry>

<dt>DMA API</dt>

<dd><p>The generic interface to provide DMA services to the clients.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Import Library</dt>

<dd><p>The DMA clients link against the <filepath>dma2.lib</filepath> file.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Platform Independent Layer (PIL)</dt>

<dd><p>The platform independent layer that contains the generic framework

independent of the baseport.</p></dd>

</dlentry>

<dlentry>

<dt>DMA HAI</dt>

<dd><p>The simplified hardware abstract interface between the platform independent

layer and platform specific layer.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Platform Specific Layer (PSL)</dt>

<dd><p>The platform specific layer is specific to the baseport and the hardware

used.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Controller (DMAC)</dt>

<dd><p>The DMAC is the hardware implementation of the DMA framework. The number

of DMAC depends on the PSL implementation.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Channel</dt>

<dd><p>The object which represents a single hardware channel. The DMA channels

are referred by a 32-bit value called as cookie. They channel object stores

the required number of descriptors for a given channel.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Channel Manager</dt>

<dd><p>The channel manager controls the DMA channels. The channel manager

functions are defined in the platform independent layer and implemented in

the platform specific layer.</p></dd>

</dlentry>

<dlentry>

<dt>DMA Descriptors</dt>

<dd><p>The data structure uses by the DMA framework to store configuration

of the data transfer block with details such as source address, destination

address, number of bytes and pointer to the next descriptor, when DMA is used

to transfer disjoined blocks of data. This structure is defined in the platform

specific layer. The DMA descriptors must not be confused with the Symbian

platform descriptors.</p></dd>

</dlentry>

<dlentry>

<dt>Descriptor Headers</dt>

<dd><p>The descriptor headers are used to store additional information about

the descriptors.</p></dd>

</dlentry>

<dlentry>

<dt>Transfer Request</dt>

<dd><p>The transfer request are the process of initialising a data transfer

by the device drivers. </p></dd>

</dlentry>

</dl></section>

<section id="GUID-F64155FC-5245-447F-88E7-C642EDEB2CEE"><title>Typical Uses</title><p>The

typical use cases of a DMA framework are:</p><ul>

<li><p>programmable data transfer between hardware controllers and memory

buffers</p></li>

<li><p>programmable data transfer of block of data between different regions

of memory</p></li>

<li><p>programmable data extraction at regular intervals in a data structure</p></li>

<li><p>programmable rotation of a two dimensional data structure in memory

such as an image.</p></li>

</ul></section>

</conbody></concept>