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SubjectPrinting to off-line printer in 2.4.0-prerelease
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Hello,

When trying to print to an off-line printer with 2.4 kernels, the
"write" system call to /dev/lp0 stalls for 10 seconds and then returns
EIO. This has the unfortunate effect that the printout will be lost,
because the redhat print filters (in rh7) use "cat" to send data to
the printer device, and cat gives up when EIO is returned.

In 2.2 kernels, the write call waited until the printer went on-line
again.

I think the problem is that the lp_write() function in lp.c calls
lp_check_status() before starting to write to the parport, and if the
printer is not ready, it simply gives up. (The LP_ABORT flag is not
used in that case.)

The following patch makes things work for me again. The kernel keeps
generating the following debug messages until the printer becomes
ready, but that doesn't seem to cause any problems.

Jan 3 18:54:27 ppro kernel: DMA write timed out
Jan 3 18:54:37 ppro kernel: parport0: FIFO is stuck
Jan 3 18:54:37 ppro kernel: parport0: BUSY timeout (1) in compat_write_block_pio
Jan 3 18:54:37 ppro kernel: lp0 off-line

Is there a better way to fix this problem?

--- linux-2.4.0-prerelease/drivers/char/lp.c.orig Wed Jan 3 18:48:39 2001
+++ linux-2.4.0-prerelease/drivers/char/lp.c Wed Jan 3 18:48:42 2001
@@ -259,7 +259,6 @@
parport_set_timeout (lp_table[minor].dev,
lp_table[minor].timeout);

- if ((retv = lp_check_status (minor)) == 0)
do {
/* Write the data. */
written = parport_write (port, kbuf, copy_size);
--- linux-2.4.0-prerelease/drivers/parport/ieee1284.c.orig Wed Jan 3 18:50:02 2001
+++ linux-2.4.0-prerelease/drivers/parport/ieee1284.c Wed Jan 3 18:50:16 2001
@@ -524,7 +524,8 @@
PARPORT_STATUS_PAPEROUT,
PARPORT_STATUS_PAPEROUT);
if (r)
- DPRINTK (KERN_INFO "%s: Timeout at event 31\n");
+ DPRINTK (KERN_INFO "%s: Timeout at event 31\n",
+ port->name);

port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;
DPRINTK (KERN_DEBUG "%s: ECP direction: forward\n",
--
Peter Österlund peter.osterlund@mailbox.swipnet.se
Sköndalsvägen 35 http://home1.swipnet.se/~w-15919
S-128 66 Sköndal +46 8 942647
Sweden

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