test for flow control in a specified priority band
Synopsis (Not in ODDI)
int bcanputnext(queue_t *q, uchar_t pri);
bcanputnext searches through the stream (starting at q->q_next)
until it finds a queue containing a service routine,
or until it reaches the end of the stream.
If found, the queue containing the service routine
is tested to see if a message in priority band pri can be enqueued.
If the band is full, bcanputnext marks the queue to automatically
back-enable the caller's service routine when the amount of data in messages
on the queue has reached its low water mark.
Pointer to a message queue.
bcanputnext returns 1
if a message of priority pri
can be sent in the stream,
or 0 if the priority band is flow-controlled.
If bcanputnext reaches the end of the stream
without finding a queue with a service routine,
then it returns 1.
The driver writer is responsible for both testing a queue with
bcanputnext and refraining from placing a message on the queue if
It is possible because of race conditions to test for room using
bcanputnext and get an indication that there is room for
a message, and then have the queue fill up before subsequently
enqueuing the message, causing a violation of flow control.
This is not a problem since the violation of flow control in this
case is bounded.
If pri is 0, the bcanputnext call is equivalent to
a call to canputnext.
Initialization, Base or Interrupt.
Does not block.
Driver defined basic locks, read/write locks, and sleep locks
may be held across calls to this function.
The caller cannot have the stream frozen (see
when calling this function.
3, 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp
19 June 2005
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005