NAME

io_speed_ctl − inform system of required transfer speed

SYNOPSIS

int io_speed_ctl (eid, speed);
int eid, speed;

DESCRIPTION

Io_speed_ctl enables you to select the data transfer speed for a data path used for a particular interface.  The transfer method (i.e., DMA, fast-handshake) chosen by the system is determined by the speed requirements. 

Eid is an entity identifier of an open HP-IB raw bus or GPIO device file obtained from an open(2), dup(2), fcntl(2), or creat(2) call.  Speed is an integer specifying the data transfer speed in K-bytes per second (one K-byte 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 enclosed in square brackets:

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

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

DEPENDENCIES

Series 300
For values of speed less than 7, the system will use  an interrupt transfer.  For larger values, DMA will be used if available; otherwise, the system will use an interrupt transfer. The default transfer method is DMA.

Series 500, 800
DMA is the only supported transfer method.

AUTHOR

Io_speed_ctl was developed by HP. 

Hewlett-Packard Company  —  Version B.1,  May 11, 2021