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List:       linux-usb-devel
Subject:    [linux-usb-devel] Digi Acceleport USB Serial Patch
From:       Al Borchers <alborchers () steinerpoint ! com>
Date:       2000-06-28 19:41:38
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Greg, Randy --

Here is a small patch to digi_acceleport.c that fixes a couple of
problems--one minor one major.   We forgot to zero the sync
field in a task structure, so our wakeup task did not get queued
in some cases and the race waking up the tty subsystem reappeared.

The patch is against 2.4.0-test3-pre1, but only changes our
digi_acceleport.c file.

I am also sending this patch and another to Vojtech for the backport.
There is another problem specific to 2.2.16 that the backport patch
fixes.

Thanks for passing these on.

-- Al
["digi_acceleport-2.4.0-test3-pre1.diff" (text/plain)]

diff -urN -X patch_ignore linux-2.4.0-test3-pre1/drivers/usb/serial/digi_acceleport.c \
                linux/drivers/usb/serial/digi_acceleport.c
--- linux-2.4.0-test3-pre1/drivers/usb/serial/digi_acceleport.c	Wed Jun 28 11:26:58 \
                2000
+++ linux/drivers/usb/serial/digi_acceleport.c	Wed Jun 28 13:28:55 2000
@@ -14,6 +14,13 @@
 *  Peter Berger (pberger@brimson.com)
 *  Al Borchers (borchers@steinerpoint.com)
 *
+*  (6/27/2000) pberger and borchers
+*    -- Zeroed out sync field in the wakeup_task before first use;
+*       otherwise the uninitialized value might prevent the task from
+*       being scheduled.
+*    -- Initialized ret value to 0 in write_bulk_callback, otherwise
+*       the uninitialized value could cause a spurious debugging message.
+*
 *  (6/22/2000) pberger and borchers
 *    -- Made cond_wait_... inline--apparently on SPARC the flags arg
 *       to spin_lock_irqsave cannot be passed to another function
@@ -134,7 +141,7 @@
 *  - Following Documentation/DocBook/kernel-locking.pdf no spin locks
 *    are held when calling copy_to/from_user or printk.
 *    
-*  $Id: digi_acceleport.c,v 1.60 2000/06/23 17:43:17 root Exp root $
+*  $Id: digi_acceleport.c,v 1.63 2000/06/28 18:28:31 root Exp root $
 */
 
 #include <linux/config.h>
@@ -321,7 +328,7 @@
 	int dp_transmit_idle;
 	int dp_in_close;
 	wait_queue_head_t dp_close_wait;	/* wait queue for close */
-	struct tq_struct dp_tasks;
+	struct tq_struct dp_wakeup_task;
 } digi_private_t;
 
 
@@ -479,6 +486,7 @@
 
 	/* wake up other tty processes */
 	wake_up_interruptible( &tty->write_wait );
+	/* For 2.2.16 backport -- wake_up_interruptible( &tty->poll_wait ); */
 
 }
 
@@ -1129,7 +1137,7 @@
 	struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
 	struct usb_serial *serial = port->serial;
 	digi_private_t *priv = (digi_private_t *)(port->private);
-	int ret;
+	int ret = 0;
 
 
 dbg( "digi_write_bulk_callback: TOP: port=%d", priv->dp_port_num );
@@ -1172,6 +1180,10 @@
 	/* wake up processes sleeping on writes immediately */
 	digi_wakeup_write( port );
 
+	/* also queue up a wakeup at scheduler time, in case we */
+	/* lost the race in write_chan(). */
+	queue_task( &priv->dp_wakeup_task, &tq_scheduler );
+
 	spin_unlock( &priv->dp_port_lock );
 
 	if( ret ) {
@@ -1179,12 +1191,6 @@
 		ret );
 	}
 
-	/* also queue up a wakeup at scheduler time, in case we */
-	/* lost the race in write_chan(). */
-	priv->dp_tasks.routine = (void *)digi_wakeup_write_lock;
-	priv->dp_tasks.data = (void *)port;
-	queue_task( &(priv->dp_tasks), &tq_scheduler );
-
 }
 
 
@@ -1486,8 +1492,10 @@
 		priv->dp_transmit_idle = 0;
 		priv->dp_in_close = 0;
 		init_waitqueue_head( &priv->dp_close_wait );
-		priv->dp_tasks.next = NULL;
-		priv->dp_tasks.data = NULL;
+		priv->dp_wakeup_task.next = NULL;
+		priv->dp_wakeup_task.sync = 0;
+		priv->dp_wakeup_task.routine = (void *)digi_wakeup_write_lock;
+		priv->dp_wakeup_task.data = (void *)(&serial->port[i]);
 		spin_lock_init( &priv->dp_port_lock );
 
 		/* initialize write wait queue for this port */


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