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PCI CD and PCI CDa

Document Number: 008-00965-06 EDT Public Revision: I December 2004

Template: edt.dot

Page 27

edt_configure_ring_buffers

Description

Configures the EDT device ring buffers. Any previous configuration is replaced, and previously

allocated buffers are released. Buffers can be allocated and maintained within the EDT device library

or within the user application itself.

Syntax

#include "edtinc.h"

int edt_configure_ring_buffers(EdtDev *edt_p, int bufsize, int nbufs,

int data_output, void *bufarray[]);

Arguments

edt_p

device handle returned from edt_open or edt_open_channel

bufsize

size of each buffer. For optimal efficiency, allocate a value approximating

throughput divided by 20: that is, if transfer occurs at 20 MB per second,

allocate 1 MB per buffer. Buffers significantly larger or smaller can overuse

memory or lock the system up in processing interrupts at this speed.

nbufs

number of buffers. Must be 1 or greater. Four is recommended for most

applications.

data_direction

Indicates whether this connection is to be used for input or output. Only one

direction is possible per device or subdevice at any given time:

EDT_READ = 0

EDT_WRITE = 1

bufarray

If NULL, the library will allocate a set of page-aligned ring buffers. If not

NULL, this argument is an array of pointers to application-allocated buffers;

these buffers must match the size and number of buffers specified in this call

and will be used as the ring buffers.

Return

0 on success; –1 on error. If all buffers cannot be allocated, none are allocated and an error is returned.

Call edt_perror() to get the system error message.

edt_buffer_addresses

Description

Returns an array containing the addresses of the ring buffers.

Syntax

#include "edtinc.h"

void **edt_buffer_addresses(EdtDev *edt_p);

Arguments

edt_p

device handle returned from edt_open or edt_open_channel.

Return

An array of pointers to the ring buffers allocated by the driver or the library. The array is indexed from

zero to n-1 where n is the number of ring buffers set in edt_configure_ring_buffers().

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