V4L/DVB (13141): gspca_sq905c: once one frame is discarded it keeps discarding all frames

While checking all gspca sub drivers pkt_scan functions for a bug I found in
1 of them (and after checking also in another), I noticed a bug in the
gspca_sq905c work queue function, once it has decided to start discarding a
frame because the application is not reading fast enough (and thus returning
buffers to fill fast enough), it never stops discarding.

This patch fixes this by simply completely removing the "discarding"
variable, if we need to discard the current frame because there is no buffer
to store it, the "frame" pointer will be NULL, so that is all we need to
check.
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/sq905c.c

@@ -119,7 +119,6 @@ static void sq905c_dostream(struct work_struct *work)
 	int bytes_left; /* bytes remaining in current frame. */
 	int data_len;   /* size to use for the next read. */
 	int act_len;
-	int discarding = 0; /* true if we failed to get space for frame. */
 	int packet_type;
 	int ret;
 	u8 *buffer;
@@ -131,8 +130,6 @@ static void sq905c_dostream(struct work_struct *work)
 	}
 
 	while (gspca_dev->present && gspca_dev->streaming) {
-		if (!gspca_dev->present)
-			goto quit_stream;
 		/* Request the header, which tells the size to download */
 		ret = usb_bulk_msg(gspca_dev->dev,
 				usb_rcvbulkpipe(gspca_dev->dev, 0x81),
@@ -150,16 +147,12 @@ static void sq905c_dostream(struct work_struct *work)
 		/* We keep the header. It has other information, too. */
 		packet_type = FIRST_PACKET;
 		frame = gspca_get_i_frame(gspca_dev);
-		if (frame && !discarding) {
+		if (frame)
 			gspca_frame_add(gspca_dev, packet_type,
 				frame, buffer, FRAME_HEADER_LEN);
-			} else
-				discarding = 1;
-		while (bytes_left > 0) {
+		while (bytes_left > 0 && gspca_dev->present) {
 			data_len = bytes_left > SQ905C_MAX_TRANSFER ?
 				SQ905C_MAX_TRANSFER : bytes_left;
-			if (!gspca_dev->present)
-				goto quit_stream;
 			ret = usb_bulk_msg(gspca_dev->dev,
 				usb_rcvbulkpipe(gspca_dev->dev, 0x81),
 				buffer, data_len, &act_len,
@@ -174,19 +167,17 @@ static void sq905c_dostream(struct work_struct *work)
 				packet_type = LAST_PACKET;
 			else
 				packet_type = INTER_PACKET;
-			frame = gspca_get_i_frame(gspca_dev);
-			if (frame && !discarding)
+			if (frame)
 				gspca_frame_add(gspca_dev, packet_type,
 						frame, buffer, data_len);
-			else
-				discarding = 1;
 		}
 	}
 quit_stream:
-	mutex_lock(&gspca_dev->usb_lock);
-	if (gspca_dev->present)
+	if (gspca_dev->present) {
+		mutex_lock(&gspca_dev->usb_lock);
 		sq905c_command(gspca_dev, SQ905C_CLEAR, 0);
-	mutex_unlock(&gspca_dev->usb_lock);
+		mutex_unlock(&gspca_dev->usb_lock);
+	}
 	kfree(buffer);
 }