linux/drivers/staging/tidspbridge/Documentation/README

                        Linux DSP/BIOS Bridge release

DSP/BIOS Bridge overview
========================

DSP/BIOS Bridge is designed for platforms that contain a GPP and one or more
attached DSPs.  The GPP is considered the master or "host" processor, and the
attached DSPs are processing resources that can be utilized by applications
and drivers running on the GPP.

The abstraction that DSP/BIOS Bridge supplies, is a direct link between a GPP
program and a DSP task.  This communication link is partitioned into two
types of sub-links:  messaging (short, fixed-length packets) and data
streaming (multiple, large buffers).  Each sub-link operates independently,
and features in-order delivery of data, meaning that messages are delivered
in the order they were submitted to the message link, and stream buffers are
delivered in the order they were submitted to the stream link.

In addition, a GPP client can specify what inputs and outputs a DSP task
uses. DSP tasks typically use message objects for passing control and status
information and stream objects for efficient streaming of real-time data.

GPP Software Architecture
=========================

A GPP application communicates with its associated DSP task running on the
DSP subsystem using the DSP/BIOS Bridge API. For example, a GPP audio
application can use the API to pass messages to a DSP task that is managing
data flowing from analog-to-digital converters (ADCs) to digital-to-analog
converters (DACs).

From the perspective of the GPP OS, the DSP is treated as just another
peripheral device.   Most high level GPP OS typically support a device driver
model, whereby applications can safely access and share a hardware peripheral
through standard driver interfaces.  Therefore, to allow multiple GPP
applications to share access to the DSP, the GPP side of DSP/BIOS Bridge
implements a device driver for the DSP.

Since driver interfaces are not always standard across GPP OS, and to provide
some level of interoperability of application code using DSP/BIOS Bridge
between GPP OS, DSP/BIOS Bridge provides a standard library of APIs which
wrap calls into the device driver.   So, rather than calling GPP OS specific
driver interfaces, applications (and even other device drivers) can use the
standard API library directly.

DSP Software Architecture
=========================

For DSP/BIOS, DSP/BIOS Bridge adds a device-independent streaming I/O (STRM)
interface, a messaging interface (NODE), and a Resource Manager (RM) Server.
The RM Server runs as a task of DSP/BIOS and is subservient to commands
and queries from the GPP.  It executes commands to start and stop DSP signal
processing nodes in response to GPP programs making requests through the
(GPP-side) API.

DSP tasks started by the RM Server are similar to any other DSP task with two
important differences:  they must follow a specific task model consisting of
three C-callable functions (node create, execute, and delete), with specific
sets of arguments, and they have a pre-defined task environment established
by the RM Server.

Tasks started by the RM Server communicate using the STRM and NODE interfaces
and act as servers for their corresponding GPP clients, performing signal
processing functions as requested by messages sent by their GPP client.
Typically, a DSP task moves data from source devices to sink devices using
device independent I/O streams, performing application-specific processing
and transformations on the data while it is moved.  For example, an audio
task might perform audio decompression (ADPCM, MPEG, CELP) on data received
from a GPP audio driver and then send the decompressed linear samples to a
digital-to-analog converter.