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SubjectRe: Printing to off-line printer in 2.4.0-prerelease
From
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Tim Waugh <twaugh@redhat.com> writes:

> --8SdtHY/0P4yzaavF
> Content-Type: text/plain; charset=us-ascii
> Content-Disposition: inline
>
> On Thu, Jan 04, 2001 at 03:39:10PM +0100, Andrea Arcangeli wrote:
>
> > As noted yesterday falling into parport_write will silenty lose data when the
> > printer is off.
>
> (Actually it depends; I think FIFO/DMA paths are fine, but yes, the
> software implementation can lose data.)

On my printer (HP LJ4MP) if parport_write is called when the printer
is off, it will lose data even in DMA mode. I added printk's to verify
that when I'm sending a 176 byte file to /dev/lp0, it will be
transferred with one call to parport_pc_fifo_write_block_dma and
/proc/interrupts says that one new parport interrupt has arrived.

> > If it's not feasible to make parport_write reliable against
> > power-off printer, then I recommend to loop in interruptible mode
> > before entering the main loop (waiting the printer to power-on) like
> > in latest patch from Peter.
>
> Have I missed a patch? How do you know whether or not the printer is
> on yet?

[...]

> If this goes away:
>
> if ((status & LP_PERRORP) && !(LP_F(minor) & LP_CAREFUL))
> /* No error. */
> last = 0;
>
> then some people might not be able to print at all.

OK, how about this patch then?

--- 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 20:34:24 2001
@@ -222,6 +222,21 @@
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 +274,7 @@
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 +294,9 @@

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;
--- 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 Thu Jan 4 20:17:10 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 20:14:17 2001
@@ -20,7 +20,7 @@
#define LP_NOPA 0x0010
#define LP_ERR 0x0020
#define LP_ABORT 0x0040
-#define LP_CAREFUL 0x0080 /* obsoleted -arca */
+#define LP_CAREFUL 0x0080
#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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