usb: gadget: uvc: set req_length based on payload by nreqs instead of req_size

Compressed formats generate content depending amount of data that is set
in the vb2 buffer by the payload_size. When streaming those formats it
is better to scatter that smaller data over all requests. This patch is
doing that by introducing the calculated req_payload_size which is
updated by each frame. It the uses this amount of data to fill the
isoc requests instead of the video->req_size.

For uncompressed formats it will not make a difference since the payload
size will be equal to the imagesize. Therefore the code will have no
effecta as req_payload_size will be equal to req_size.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20240403-uvc_request_length_by_interval-v7-6-e224bb1035f0@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 731e3b9d21ac..6757a4e25a74 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -58,6 +58,7 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 static int uvc_buffer_prepare(struct vb2_buffer *vb)
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
+	struct uvc_video *video = container_of(queue, struct uvc_video, queue);
 	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
 	struct uvc_buffer *buf = container_of(vbuf, struct uvc_buffer, buf);
 
@@ -78,10 +79,15 @@ static int uvc_buffer_prepare(struct vb2_buffer *vb)
 		buf->mem = vb2_plane_vaddr(vb, 0);
 	}
 	buf->length = vb2_plane_size(vb, 0);
-	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
 		buf->bytesused = 0;
-	else
+	} else {
 		buf->bytesused = vb2_get_plane_payload(vb, 0);
+		buf->req_payload_size =
+			  DIV_ROUND_UP(buf->bytesused +
+				       (video->reqs_per_frame * UVCG_REQUEST_HEADER_LEN),
+				       video->reqs_per_frame);
+	}
 
 	return 0;
 }