DGS Driver
2-84
Important Note:
This driver will no longer be supported in the next
major release of DSP/BIOS. We recommend that you use the IOM
driver interface instead. See the
DSP/BIOS Driver Developer’s Guide
(SPRU616). This driver is still supported in DSP/BIOS 5.32 and will be
supported in any patch releases or minor enhancements to DSP/BIOS
5.32.
Description
The DGS driver manages a class of stackable devices which compress
or expand a data stream by applying a user-supplied function to each
input or output buffer. This driver might be used to pack data buffers
before writing them to a disk file or to unpack these same buffers when
reading from a disk file. All (un)packing must be completed on frame
boundaries as this driver (for efficiency) does not maintain remainders
across I/O operations.
On opening a DGS device by name, DGS uses the unmatched portion of
the string to recursively open an underlying device.
This driver requires a transform function and a packing/unpacking ratio
which are used when packing/unpacking buffers to/from the underlying
device.
Configuring a DGS
Device
To create a DGS device object in a configuration script, use the following
syntax:
var myDgs = bios.UDEV.create("myDgs");
Modify the myDgs properties as follows.
❏
init function.
Type 0 (zero).
❏
function table ptr.
Type _DGS_FXNS
❏
function table type
. DEV_Fxns
❏
device id.
Type 0 (zero).
❏
device params ptr.
Type 0 (zero) to use the default parameters. To
use different values, you must declare a DGS_Params structure (as
described after this list) containing the values to use for the
parameters.
DGS Driver
Stackable gather/scatter driver