Hi Michael,
Thank you for the patch.
On Sun, Apr 03, 2022 at 01:39:11AM +0200, Michael Grzeschik wrote:
> The current limitation of possible number of requests being handled is
> dependent on the gadget speed. It makes more sense to depend on the
> typical frame size when calculating the number of requests. This patch
> is changing this and is using the previous limits as boundaries for
> reasonable minimum and maximum number of requests.
What are typical values you get for the number of requests in your use
cases with this change ? Could you mention them in the commit message ?
> Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
> ---
> drivers/usb/gadget/function/uvc_queue.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
> index cfa0ac4adb04d5..2a091cf07981e1 100644
> --- a/drivers/usb/gadget/function/uvc_queue.c
> +++ b/drivers/usb/gadget/function/uvc_queue.c
> @@ -44,7 +44,8 @@ static int uvc_queue_setup(struct vb2_queue *vq,
> {
> struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> struct uvc_video *video = container_of(queue, struct uvc_video, queue);
> - struct usb_composite_dev *cdev = video->uvc->func.config->cdev;
> + unsigned int req_size;
> + unsigned int nreq;
>
> if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
> *nbuffers = UVC_MAX_VIDEO_BUFFERS;
> @@ -53,10 +54,14 @@ static int uvc_queue_setup(struct vb2_queue *vq,
>
> sizes[0] = video->imagesize;
>
> - if (cdev->gadget->speed < USB_SPEED_SUPER)
> - video->uvc_num_requests = 4;
> - else
> - video->uvc_num_requests = 64;
> + req_size = video->ep->maxpacket
> + * max_t(unsigned int, video->ep->maxburst, 1)
> + * (video->ep->mult);
> +
> + nreq = DIV_ROUND_UP(DIV_ROUND_UP(sizes[0], 2), req_size);
Where does the division by 2 come from ?
> + nreq = min_t(unsigned int, nreq, 64);
> + nreq = max_t(unsigned int, nreq, 4);
You can use clamp():
video->uvc_num_requests = clamp(nreq, 4U, 64U);
> + video->uvc_num_requests = nreq;
>
> return 0;
> }
--
Regards,
Laurent Pinchart
