patch-2.4.26 linux-2.4.26/drivers/usb/printer.c

• Lines: 66
• Date: 2004-04-14 06:05:33.000000000 -0700
• Orig file: linux-2.4.25/drivers/usb/printer.c
• Orig date: 2004-02-18 05:36:31.000000000 -0800

diff -urN linux-2.4.25/drivers/usb/printer.c linux-2.4.26/drivers/usb/printer.c
@@ -604,14 +604,16 @@
 {
 	DECLARE_WAITQUEUE(wait, current);
 	struct usblp *usblp = file->private_data;
-	int timeout, err = 0;
+	int timeout, err = 0, transfer_length = 0;
 	size_t writecount = 0;
 
 	while (writecount < count) {
 		if (!usblp->wcomplete) {
 			barrier();
-			if (file->f_flags & O_NONBLOCK)
-				return -EAGAIN;
+			if (file->f_flags & O_NONBLOCK) {
+				writecount += transfer_length;
+				return writecount ? writecount : -EAGAIN;
+			}
 
 			timeout = USBLP_WRITE_TIMEOUT;
 			add_wait_queue(&usblp->wait, &wait);
@@ -655,27 +657,36 @@
 			continue;
 		}
 
-		writecount += usblp->writeurb->transfer_buffer_length;
-		usblp->writeurb->transfer_buffer_length = 0;
-
+		/* We must increment writecount here, and not at the
+		 * end of the loop. Otherwise, the final loop iteration may
+		 * be skipped, leading to incomplete printer output.
+		 */
+		writecount += transfer_length;
 		if (writecount == count) {
 			up (&usblp->sem);
 			break;
 		}
 
-		usblp->writeurb->transfer_buffer_length = (count - writecount) < USBLP_BUF_SIZE ?
-							  (count - writecount) : USBLP_BUF_SIZE;
+		transfer_length = count - writecount;
+		if(transfer_length > USBLP_BUF_SIZE) 
+			transfer_length = USBLP_BUF_SIZE;
+		
+		usblp->writeurb->transfer_buffer_length = transfer_length;
 
-		if (copy_from_user(usblp->writeurb->transfer_buffer, buffer + writecount,
-				usblp->writeurb->transfer_buffer_length)) {
+		if (copy_from_user(usblp->writeurb->transfer_buffer, 
+				   buffer + writecount, transfer_length)) {
 			up(&usblp->sem);
 			return writecount ? writecount : -EFAULT;
 		}
 
 		usblp->writeurb->dev = usblp->dev;
 		usblp->wcomplete = 0;
-		if (usb_submit_urb(usblp->writeurb)) {
-			count = -EIO;
+		err = usb_submit_urb(usblp->writeurb);
+		if (err) {
+			if (err != -ENOMEM)
+				count = -EIO;
+			else
+				count = writecount ? writecount : -ENOMEM;
 			up (&usblp->sem);
 			break;
 		}