usb: gadget: uvc: giveback vb2 buffer on req complete

On uvc_video_encode_isoc_sg the mapped vb2 buffer is returned
to early. Only after the last usb_request worked with the buffer
it is allowed to give it back to vb2. This patch fixes that.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20220402232744.3622565-3-m.grzeschik@pengutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/uvc.h

@@ -79,6 +79,7 @@ struct uvc_request {
 	struct uvc_video *video;
 	struct sg_table sgt;
 	u8 header[UVCG_REQUEST_HEADER_LEN];
+	struct uvc_buffer *last_buf;
 };
 
 struct uvc_video {

drivers/usb/gadget/function/uvc_queue.c

@@ -325,8 +325,6 @@ void uvcg_complete_buffer(struct uvc_video_queue *queue,
 		return;
 	}
 
-	list_del(&buf->queue);
-
 	buf->buf.field = V4L2_FIELD_NONE;
 	buf->buf.sequence = queue->sequence++;
 	buf->buf.vb2_buf.timestamp = ktime_get_ns();

drivers/usb/gadget/function/uvc_video.c

@@ -112,6 +112,7 @@ uvc_video_encode_bulk(struct usb_request *req, struct uvc_video *video,
 	if (buf->bytesused == video->queue.buf_used) {
 		video->queue.buf_used = 0;
 		buf->state = UVC_BUF_STATE_DONE;
+		list_del(&buf->queue);
 		uvcg_complete_buffer(&video->queue, buf);
 		video->fid ^= UVC_STREAM_FID;
 
@@ -183,8 +184,9 @@ uvc_video_encode_isoc_sg(struct usb_request *req, struct uvc_video *video,
 		video->queue.buf_used = 0;
 		buf->state = UVC_BUF_STATE_DONE;
 		buf->offset = 0;
-		uvcg_complete_buffer(&video->queue, buf);
+		list_del(&buf->queue);
 		video->fid ^= UVC_STREAM_FID;
+		ureq->last_buf = buf;
 	}
 }
 
@@ -210,6 +212,7 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
 	if (buf->bytesused == video->queue.buf_used) {
 		video->queue.buf_used = 0;
 		buf->state = UVC_BUF_STATE_DONE;
+		list_del(&buf->queue);
 		uvcg_complete_buffer(&video->queue, buf);
 		video->fid ^= UVC_STREAM_FID;
 	}
@@ -264,6 +267,11 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
 		uvcg_queue_cancel(queue, 0);
 	}
 
+	if (ureq->last_buf) {
+		uvcg_complete_buffer(&video->queue, ureq->last_buf);
+		ureq->last_buf = NULL;
+	}
+
 	spin_lock_irqsave(&video->req_lock, flags);
 	list_add_tail(&req->list, &video->req_free);
 	spin_unlock_irqrestore(&video->req_lock, flags);
@@ -332,6 +340,7 @@ uvc_video_alloc_requests(struct uvc_video *video)
 		video->ureq[i].req->complete = uvc_video_complete;
 		video->ureq[i].req->context = &video->ureq[i];
 		video->ureq[i].video = video;
+		video->ureq[i].last_buf = NULL;
 
 		list_add_tail(&video->ureq[i].req->list, &video->req_free);
 		/* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */