Commit 310c8c32 authored by Marko Kohtala's avatar Marko Kohtala Committed by Linus Torvalds
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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: default avatarMarko Kohtala <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 742ec650
......@@ -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;
&& 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);
last_dev = !(parport_read_status (port)
/* See if this device thought it was the last in the
* chain. */
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);
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