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/* $Id: parport_ieee1284.c,v 1.4 1997/10/19 21:37:21 philip Exp $
* IEEE-1284 implementation for parport.
*
* Authors: Phil Blundell <Philip.Blundell@pobox.com>
* Carsten Gross <carsten@sol.wohnheim.uni-ulm.de>
* Jose Renau <renau@acm.org>
*/
#include <linux/tasks.h>
#include <linux/parport.h>
#include <linux/delay.h>
#include <linux/kernel.h>
/* Wait for Status line(s) to change in 35 ms - see IEEE1284-1994 page 24 to
* 25 for this. After this time we can create a timeout because the
* peripheral doesn't conform to IEEE1284. We want to save CPU time: we are
* waiting a maximum time of 500 us busy (this is for speed). If there is
* not the right answer in this time, we call schedule and other processes
* are able to eat the time up to 40ms.
*/
int parport_wait_peripheral(struct parport *port, unsigned char mask,
unsigned char result)
{
int counter;
unsigned char status;
for (counter = 0; counter < 20; counter++) {
status = parport_read_status(port);
if ((status & mask) == result)
return 0;
udelay(25);
if (current->need_resched)
schedule();
}
current->state = TASK_INTERRUPTIBLE;
schedule_timeout(HZ/25); /* wait for 40ms */
status = parport_read_status(port);
return ((status & mask) == result)?0:1;
}
/* Test if the peripheral is IEEE 1284 compliant.
* return values are:
* 0 - handshake failed; peripheral is not compliant (or none present)
* 1 - handshake OK; IEEE1284 peripheral present but no data available
* 2 - handshake OK; IEEE1284 peripheral and data available
*/
int parport_ieee1284_nibble_mode_ok(struct parport *port, unsigned char mode)
{
/* make sure it's a valid state, set nStrobe & nAutoFeed high */
parport_write_control(port, (parport_read_control(port) \
& ~1 ) & ~2);
udelay(1);
parport_write_data(port, mode);
udelay(1);
/* nSelectIn high, nAutoFd low */
parport_write_control(port, (parport_read_control(port) & ~8) | 2);
if (parport_wait_peripheral(port, 0x78, 0x38)) {
parport_write_control(port,
(parport_read_control(port) & ~2) | 8);
return 0;
}
/* nStrobe low */
parport_write_control(port, parport_read_control(port) | 1);
udelay(1); /* Strobe wait */
/* nStrobe high, nAutoFeed low, last step before transferring
* reverse data */
parport_write_control(port, (parport_read_control(port) \
& ~1) & ~2);
udelay(1);
/* Data available? */
return (parport_wait_peripheral(port, 0x20, 0))?1:2;
}
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