Re: [PATCH v4 06/10] usb: gadget: uvc: set req_size once when the vb2 queue is calculated

Laurent Pinchart
2024-08-13T09:41:35Z

On Tue, Aug 13, 2024 at 11:09:30AM +0200, Michael Grzeschik wrote:
> The uvc gadget driver is calculating the req_size on every
> video_enable/alloc_request and is based on the fixed configfs parameters
> maxpacket, maxburst and mult.
>
> As those parameters can not be changed once the gadget is started and
> the same calculation is done already early on the
> vb2_streamon/queue_setup path its save to remove one extra calculation
> and reuse the calculation from uvc_queue_setup for the allocation step.

Avoiding double calculations is good, but then don't compute the value
in uvc_queue_setup(). That will also be called multiple times, and its
timing will be controlled by userspace. Move it to a better location.

> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>
> ---
> v3 -> v4: -
> v2 -> v3: -
> v1 -> v2: -
> ---
> drivers/usb/gadget/function/uvc_queue.c | 2 ++
> drivers/usb/gadget/function/uvc_video.c | 15 ++-------------
> 2 files changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
> index 7995dd3fef184..2414d78b031f4 100644
> --- a/drivers/usb/gadget/function/uvc_queue.c
> +++ b/drivers/usb/gadget/function/uvc_queue.c
> @@ -63,6 +63,8 @@ static int uvc_queue_setup(struct vb2_queue *vq,
> */
> nreq = DIV_ROUND_UP(DIV_ROUND_UP(sizes[0], 2), req_size);
> nreq = clamp(nreq, 4U, 64U);
> +
> + video->req_size = req_size;
> video->uvc_num_requests = nreq;
>
> return 0;
> diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
> index 259920ae36843..a6786beef91ad 100644
> --- a/drivers/usb/gadget/function/uvc_video.c
> +++ b/drivers/usb/gadget/function/uvc_video.c
> @@ -480,7 +480,6 @@ uvc_video_free_requests(struct uvc_video *video)
> INIT_LIST_HEAD(&video->ureqs);
> INIT_LIST_HEAD(&video->req_free);
> INIT_LIST_HEAD(&video->req_ready);
> - video->req_size = 0;
> return 0;
> }
>
> @@ -488,16 +487,9 @@ static int
> uvc_video_alloc_requests(struct uvc_video *video)
> {
> struct uvc_request *ureq;
> - unsigned int req_size;
> unsigned int i;
> int ret = -ENOMEM;
>
> - BUG_ON(video->req_size);
> -
> - req_size = video->ep->maxpacket
> - * max_t(unsigned int, video->ep->maxburst, 1)
> - * (video->ep->mult);
> -
> for (i = 0; i < video->uvc_num_requests; i++) {
> ureq = kzalloc(sizeof(struct uvc_request), GFP_KERNEL);
> if (ureq == NULL)
> @@ -507,7 +499,7 @@ uvc_video_alloc_requests(struct uvc_video *video)
>
> list_add_tail(&ureq->list, &video->ureqs);
>
> - ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
> + ureq->req_buffer = kmalloc(video->req_size, GFP_KERNEL);
> if (ureq->req_buffer == NULL)
> goto error;
>
> @@ -525,12 +517,10 @@ uvc_video_alloc_requests(struct uvc_video *video)
> list_add_tail(&ureq->req->list, &video->req_free);
> /* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
> sg_alloc_table(&ureq->sgt,
> - DIV_ROUND_UP(req_size - UVCG_REQUEST_HEADER_LEN,
> + DIV_ROUND_UP(video->req_size - UVCG_REQUEST_HEADER_LEN,
> PAGE_SIZE) + 2, GFP_KERNEL);
> }
>
> - video->req_size = req_size;
> -
> return 0;
>
> error:
> @@ -663,7 +653,6 @@ uvcg_video_disable(struct uvc_video *video)
> INIT_LIST_HEAD(&video->ureqs);
> INIT_LIST_HEAD(&video->req_free);
> INIT_LIST_HEAD(&video->req_ready);
> - video->req_size = 0;
> spin_unlock_irqrestore(&video->req_lock, flags);
>
> /*

--
Regards,

Laurent Pinchart