NAME

       ieee1284_read_status, ieee1284_wait_status - analyse status lines

SYNOPSIS

       #include <ieee1284.h>

       int ieee1284_read_status(struct parport *port);

       int ieee1284_wait_status(struct parport *port, unsigned char mask, unsigned char val,
                                struct timeval *timeout);

DESCRIPTION

       There are five status lines, one of which is usually inverted on PC-style ports. Where
       they differ, libieee1284 operates on the IEEE 1284 values, not the PC-style inverted
       values. The status lines are represented by the following enumeration:

           enum ieee1284_status_bits
           {
             S1284_NFAULT = 0x08,
             S1284_SELECT = 0x10,
             S1284_PERROR = 0x20,
             S1284_NACK   = 0x40,
             S1284_BUSY   = 0x80,
             /* To convert those values into PC-style register values, use this: */
             S1284_INVERTED = S1284_BUSY,
           };

       These functions all act on the parallel port associated with port, which must be claimed.

       The purpose of ieee1284_wait_status is to wait until particular status lines have
       specified values. Its timeout parameter may be modified on return.

RETURN VALUE

       For ieee1284_read_status, the return value is a non-negative integer with bits set as
       appropriate representing the status lines. A negative result indicates an error.

       For ieee1284_wait_status, the return value is E1284_OK if the status lines now reflect the
       desired values (i.e. status & mask is val), or a negative result indicating an error.

       Possible error codes:

       E1284_NOTIMPL
           The port lacks the required capability. This could be due to a limitation of this
           version of libieee1284, or a hardware limitation.

       E1284_NOTAVAIL
           Access to the status lines is not available on this port type.

       E1284_TIMEDOUT
           The timeout has elapsed.

       E1284_INVALIDPORT
           The port parameter is invalid (for instance, perhaps the port is not claimed).

NOTES

       The nAck pin is often able to trigger interrupts on the host machine. With operating
       system help these interrupts may be visible to the application via the file descriptor
       returned by ieee1284_get_irq_fd.

       Under Linux, the conditions are that the parallel port driver knows which interrupt line
       to use and is using it, and that the relevant /dev/parport device node is accessible and
       backed by a device driver.

AUTHOR

       Tim Waugh <twaugh@redhat.com>
           Author.

COPYRIGHT

       Copyright © 2001-2003 Tim Waugh

                                            09/18/2007                         IEEE1284_STATUS(3)