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[PATCH] parport: daisy chain end detection fix 

Daisy chain end detection failed at least with older daisy chain devices that
do not implement the last device signal.

Signed-off-by: Marko Kohtala <marko.kohtala@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Marko Kohtala 2006-01-06 00:19:45 -08:00 committed by Linus Torvalds
parent 742ec650e9
commit 310c8c324f
1 changed files with 17 additions and 10 deletions
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27
drivers/parport/daisy.c
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@ -436,7 +436,7 @@ static int select_port (struct parport *port)
static int assign_addrs (struct parport *port)
{
unsigned char s, last_dev;
unsigned char s;
unsigned char daisy;
int thisdev = numdevs;
int detected;
@ -472,10 +472,13 @@ static int assign_addrs (struct parport *port)
}
parport_write_data (port, 0x78); udelay (2);
last_dev = 0; /* We've just been speaking to a device, so we
know there must be at least _one_ out there. */
s = parport_read_status (port);
for (daisy = 0; daisy < 4; daisy++) {
for (daisy = 0;
(s & (PARPORT_STATUS_PAPEROUT|PARPORT_STATUS_SELECT))
== (PARPORT_STATUS_PAPEROUT|PARPORT_STATUS_SELECT)
&& daisy < 4;
++daisy) {
parport_write_data (port, daisy);
udelay (2);
parport_frob_control (port,
@ -485,14 +488,18 @@ static int assign_addrs (struct parport *port)
parport_frob_control (port, PARPORT_CONTROL_STROBE, 0);
udelay (1);
if (last_dev)
/* No more devices. */
add_dev (numdevs++, port, daisy);
/* See if this device thought it was the last in the
* chain. */
if (!(s & PARPORT_STATUS_BUSY))
break;
last_dev = !(parport_read_status (port)
& PARPORT_STATUS_BUSY);
add_dev (numdevs++, port, daisy);
/* We are seeing pass through status now. We see
last_dev from next device or if last_dev does not
work status lines from some non-daisy chain
device. */
s = parport_read_status (port);
}
parport_write_data (port, 0xff); udelay (2);