usblp: continuously poll for status

The usblp in 2.6.18 polled for status regardless if we actually needed it.
At some point I dropped it, to save the batteries if nothing else.
As it turned out, printers exist (e.g. Canon BJC-3000) that need prodding
this way or else they stop. This patch restores the old behaviour.
If you want to save battery, don't leave jobs in the print queue.

I tested this on my printers by printing and examining usbmon traces
to make sure status is being requested and printers continue to print.
Tuomas Jäntti verified the fix on BJC-3000.
Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/usblp.c

@@ -880,16 +880,19 @@ static int usblp_wwait(struct usblp *usblp, int nonblock)
 		if (rc <= 0)
 			break;
 
+		if (schedule_timeout(msecs_to_jiffies(1500)) == 0) {
 			if (usblp->flags & LP_ABORT) {
-			if (schedule_timeout(msecs_to_jiffies(5000)) == 0) {
 				err = usblp_check_status(usblp, err);
 				if (err == 1) {	/* Paper out */
 					rc = -ENOSPC;
 					break;
 				}
-			}
 			} else {
-			schedule();
+				/* Prod the printer, Gentoo#251237. */
+				mutex_lock(&usblp->mut);
+				usblp_read_status(usblp, usblp->statusbuf);
+				mutex_unlock(&usblp->mut);
+			}
 		}
 	}
 	set_current_state(TASK_RUNNING);