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SubjectRe: Printing to off-line printer in 2.4.0-prerelease
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Andrea Arcangeli <andrea@suse.de> writes:

> On Wed, Jan 03, 2001 at 10:00:59PM +0100, Peter Osterlund wrote:
> > off. Apparently the printer tells the computer it is OK to send data
> > to it when it is off.
>
> So then parport_write is probably buggy because it's losing data silenty while
> the printer is off. So the below is probably a band aid. Really some printer
> acts in a different way (see the LP_CAREFUL hack in 2.2.x) so it maybe that
> parport_write is ok on some printer and it would need something like a
> LP_CAREFUL option to work also on some other printer. Or maybe some parport
> handshake is badly designed in hardware and it cannot report errors (or maybe
> there's the hardware compatibility mode that cannot know about LP_CAREFUL to
> workaround some printer behaviour). In such case your patch is probably the
> only way to go (but almost certainly for the software compatibility mode it
> should be possible to report errors via parport_write as we do in 2.2.x).

The tunelp man-page seems to think there are printers that need the
LP_CAREFUL handling. I also noted that if I disconnect my printer from
the computer, the data will no longer be lost. Apparently the printer
confuses the parallel port when it is powered off.

> > I also only get one DMA write timeout when putting the printer in
> > offline mode during sending, instead of repeated timeouts as I got
> > with the previous patch.
>
> I see, it makes sense to try to parport_write only when errors goes away, but I
> think it's nicer to have lp_error or lp_check_status that loops internally in
> interruptible mode if LP_ABORT isn't set via lptune. probably the code should
> be restructured a bit.

What do you think about the following patch? It also works for all the
tests mentioned in my previous message.

--- 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 Thu Jan 4 00:45:52 2001
@@ -188,10 +188,7 @@
int error = 0;
unsigned int last = lp_table[minor].last_error;
unsigned char status = r_str(minor);
- if ((status & LP_PERRORP) && !(LP_F(minor) & LP_CAREFUL))
- /* No error. */
- last = 0;
- else if ((status & LP_POUTPA)) {
+ if ((status & LP_POUTPA)) {
if (last != LP_POUTPA) {
last = LP_POUTPA;
printk(KERN_INFO "lp%d out of paper\n", minor);
@@ -210,8 +207,7 @@
}
error = -EIO;
} else {
- last = 0; /* Come here if LP_CAREFUL is set and no
- errors are reported. */
+ last = 0; /* Come here if no errors are reported. */
}

lp_table[minor].last_error = last;
@@ -222,6 +218,21 @@
return error;
}

+static int lp_wait_ready(int minor)
+{
+ int error = 0;
+ do {
+ error = lp_check_status (minor);
+ if (error && (LP_F(minor) & LP_ABORT))
+ break;
+ if (signal_pending (current)) {
+ error = -EINTR;
+ break;
+ }
+ } while (error);
+ return error;
+}
+
static ssize_t lp_write(struct file * file, const char * buf,
size_t count, loff_t *ppos)
{
@@ -259,7 +270,7 @@
parport_set_timeout (lp_table[minor].dev,
lp_table[minor].timeout);

- if ((retv = lp_check_status (minor)) == 0)
+ if ((retv = lp_wait_ready (minor)) == 0)
do {
/* Write the data. */
written = parport_write (port, kbuf, copy_size);
@@ -279,9 +290,9 @@

if (copy_size > 0) {
/* incomplete write -> check error ! */
- int error = lp_check_status (minor);
+ int error = lp_wait_ready (minor);

- if (LP_F(minor) & LP_ABORT) {
+ if (error) {
if (retv == 0)
retv = error;
break;
@@ -453,10 +464,7 @@
LP_F(minor) &= ~LP_ABORTOPEN;
break;
case LPCAREFUL:
- if (arg)
- LP_F(minor) |= LP_CAREFUL;
- else
- LP_F(minor) &= ~LP_CAREFUL;
+ /* Obsolete */
break;
case LPWAIT:
LP_WAIT(minor) = arg;
--- 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 21:32:28 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",
--- linux-2.4.0-prerelease/include/linux/lp.h.orig Thu Jan 4 00:21:15 2001
+++ linux-2.4.0-prerelease/include/linux/lp.h Thu Jan 4 00:21:21 2001
@@ -20,7 +20,6 @@
#define LP_NOPA 0x0010
#define LP_ERR 0x0020
#define LP_ABORT 0x0040
-#define LP_CAREFUL 0x0080 /* obsoleted -arca */
#define LP_ABORTOPEN 0x0100

#define LP_TRUST_IRQ_ 0x0200 /* obsolete */
--
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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