BSP Developer's Guide

VxWorks 5.5
BSP Developer’s Guide
DEVICE_WRITES_ASYNCHRONOUSLY
The hardware provides asynchronous write operations to shared memory.
This attribute is TRUE if the device can perform write operations to shared
memory asynchronously to driver activity.
SHARED_CACHE_LINES
The hardware allows both the driver and the device to write to a single cache
line. If any single cache line can be written by both the driver and the device,
this attribute is TRUE. An example of this is a shared data structure such as this
one:
struct
{
short command;
short status
};
In this case, the driver is responsible for writing the command field and the
device is responsible for writing the status field.
SNOOPED
The hardware provides bus snooping. This attribute is TRUE if the target
hardware supports bus snooping. Bus snooping makes cache issues transparent
to the driver. Only full bus snooping that maintains full coherency is
supported. Some processors provide partial snooping that does not meet the
requirements of full memory coherency. Without full snooping, this attribute
must be FALSE.
SHARED_POINTERS
The device’s control model allows the driver and the device to exchange
memory pointers. This attribute is TRUE if the driver and the device exchange
memory pointers.
5.8.3 Developing the cacheLib Strategy
This section describes how to devise a cacheLib strategy based on your driver’s
attributes.
Before proceeding, establish the target range that the driver is to support—for
example, a single target, multiple differing targets, or broad support. This decision
affects your choice of cache strategy. For example, a driver intended for broad
support can be restricted to certain cacheLib routines because target specifics are
unknown. However, drivers intended to support only a single known target can
be designed to use the cacheLib routines that make best use of the target hardware.
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