NAME

io_speed_ctl() − inform system of required transfer speed

SYNOPSIS

#include <dvio.h>

int io_speed_ctl(int eid, int speed);

DESCRIPTION

io_speed_ctl() selects the data transfer speed for a data path used for a particular interface.  The transfer method (i.e., DMA or fast-handshake) chosen by the system is determined by the speed requirements. 

eid is an entity identifier of an open HP-IB raw bus, Centronics-compatible parallel, or GPIO device file obtained from an open(), dup(), fcntl(), or creat() call.  speed is an integer specifying the data transfer speed in Kbytes per second (one Kbyte equals 1024 bytes). 

RETURN VALUE

io_speed_ctl() returns 0 if successful, and −1 otherwise. 

ERRORS

io_speed_ctl() fails under the following condition, and sets errno to the value indicated:

[ENOTTY] eid does not refer to channel device file. 

[EBADF] eid does not refer to an open file. 

DEPENDENCIES

Series 300/400:

For values of speed less than 7, the system uses an interrupt transfer.  For larger values, DMA is used if available; otherwise, the system uses an interrupt transfer.  The default transfer method is DMA. 

Series 800:

DMA is the only supported transfer method. 

AUTHOR

io_speed_ctl() was developed by HP. 

Hewlett-Packard Company  —  HP-UX Release 9.10: April 1995