blmode.7 (2010 09)

blmode(7) blmode(7)

On systems that support process group control, ioctl requests are restricted from use by background

processes, unless otherwise noted for a speciﬁc request. An attempt to issue an ioctl request from a back-

ground process causes the process to block and may cause a

SIGTTOU signal to be sent to the process

group.

The primary ioctl (2) calls have the form:

int ioctl(int fildes, int request, struct blmodeio *arg);

Requests using this form include:

CBGETA Get the parameters associated with the block mode interface and store them in the

blmodeio structure referenced by arg . This request is allowed from a background

process. However, the information may be subsequently changed by a foreground

process.

CBSETA Set the parameters associated with the block mode interface from the blmodeio

structure referenced by arg. The change is immediate.

RETURN VALUE

Refer to read (2), write (2), and ioctl (2).

ERRORS

If an error value is returned during a read, it is possible for the user’s buffer to be altered. In this case,

the data in the user’s buffer should be ignored because it is incomplete.

The global variable errno will be set to indicate the following error, in addition to those errors described

on read (2), write (2), and ioctl (2):

[EIO] A read error occurred during the transmission of the block mode data block.

WARNINGS

The [EIO] error that is returned for read errors can be caused by many events. The read returns [EIO]

for transmission, framing, parity, break, and overrun errors, or if the internal timer expires. The inter-

nal timer starts when the second trigger character is sent by the computer, and ends when the terminat-

ing character is received by the computer. The length of this timer is determined by the number of bytes

requested in the read and the current baud rate, plus an additional ten seconds.

AUTHOR

The blmode driver was developed by HP.