CentOS 7.0 - man page for ieee1284_read_data (centos section 3)
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IEEE1284_DATA(3) Functions IEEE1284_DATA(3)
ieee1284_read_data, ieee1284_write_data, ieee1284_data_dir, ieee1284_wait_data - control
the data lines
int ieee1284_read_data(struct parport *port);
void ieee1284_write_data(struct parport *port, unsigned char dt);
int ieee1284_data_dir(struct parport *port, int reverse);
int ieee1284_wait_data(struct parport *port, unsigned char mask, unsigned char val,
struct timeval *timeout);
These functions manipulate the data lines of the parallel port associated with port (which
must have been claimed using ieee1284_claim(3)). The lines are represented by an 8-bit
number (one line per bit) and a direction. The data lines are driven as a group; they may
be all host-driven (forward direction) or not (reverse direction). When the peripheral is
driving them the host must not.
For ieee1284_data_dir the reverse parameter should be zero to turn the data line drivers
on and non-zero to turn them off. Some port types may be unable to switch off the data
Setting the data lines may have side effects on some port types (for example, some Amiga
ports pulse nStrobe).
ieee1284_wait_data waits, up until the timeout, for the data bits specified in mask to
have the corresponding values in val.
ieee1284_read_data returns the 8-bit number representing the data lines unless it is not
possible to return such a value with this port type, in which case it returns an error
code. Possible error codes:
Bi-directional data lines are not available on this system.
The port parameter is invalid (perhaps it has not been claimed, for instance).
There was an error at the operating system level, and errno has been set accordingly.
The timeout has elapsed.
Whereas ieee1284_read_data may return E1284_NOTAVAIL on its first invocation on the port,
if it does not do so then it cannot until ieee1284_close is called for that port.
Tim Waugh <firstname.lastname@example.org>
Copyright (C) 2001-2003 Tim Waugh
[FIXME: source] 06/17/2014 IEEE1284_DATA(3)
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