PM8621-BI PMC-Sierra, Inc., PM8621-BI Datasheet - Page 198

• Manufacturer Part Number: PM8621-BI
• Description: Driver, NSE/SBS Narrowband Chipset Driver
• Manufacturer: PMC-Sierra, Inc.

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2021248, Issue 1
A
This appendix describes the driver abstraction layer (DAL) between the CSD and the underlying
device drivers. Acting as a “shim” layer between the CSD and the underlying device driver(s), the
DAL can be viewed as a translation layer bridging the interface difference between the CSD and
the low level drivers. When a CSD call is made by the upper layer application, the DAL
dispatches the call to the appropriate underlying device driver(s) for the operation. In addition, the
DAL deciphers messages from the device driver(s) to the CSD, e.g., ISR callback messages and
error codes.
The purpose of the DAL is to decouple the CSD from the underlying device drivers. The reason is
two-fold: (1) the CSD can more easily adapt to various system configurations. (2) allows porting
of the CSD to any future device(s) that may provide similar time:space:time switching
capabilities, as the SBS and NSE devices.
In a centralized configuration with SBS and NSE devices, the DAL is implemented to interact
with both the SBS and NSE device drivers. In a distributed configuration where the SBS or NSE
devices may be absent, the DAL can be implemented to exclude any of the calls to a device driver
that is absent. For instance, in a core NSE card without any SBS devices, calls to the SBS driver
can be implemented as “empty” functions that returns immediately upon invocation. No actual
reference to any SBS driver calls is made.
The DAL lends itself to the porting of the CSD to any future devices that may provide similar
time:space:time fabric capabilities. The CSD will be shielded from a change of underlying
devices and changes are local to the DAL only. The CSD functionality can then be leveraged and
reused in systems built with future switching devices.
The DAL is modeled after a generic time switch device driver and a space switch one. It
comprises the space switch DAL and the time switch DAL. Arranged in logical blocks, the
following sections describe the DAL interface.
PPENDIX
G: D
RIVER
A
BSTRACTION
Narrowband Chipset Device Driver Manual
Appendix G: Driver Abstraction Layer (DAL)
L
AYER
(DAL)
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