Commit 010dc57c authored by Xu Yang's avatar Xu Yang Committed by Greg Kroah-Hartman
Browse files

usb: gadget: uvc: fix interval_duration calculation 



According to USB specification:

  For full-/high-speed isochronous endpoints, the bInterval value is
  used as the exponent for a 2^(bInterval-1) value.

To correctly convert bInterval as interval_duration:
  interval_duration = 2^(bInterval-1) * frame_interval

Because the unit of video->interval is 100ns, add a comment info to
make it clear.

Fixes: 48dbe731 ("usb: gadget: uvc: set req_size and n_requests based on the frame interval")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarFrank Li <Frank.Li@nxp.com>
Signed-off-by: default avatarXu Yang <xu.yang_2@nxp.com>
Link: https://patch.msgid.link/20260113-uvc-gadget-fix-patch-v2-2-62950ef5bcb5@nxp.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2edc1acb

drivers/usb/gadget/function/uvc.h

+1 −1
Original line number Diff line number Diff line
@@ -107,7 +107,7 @@ struct uvc_video { 
	unsigned int width;

	unsigned int height;

	unsigned int imagesize;

	unsigned int interval;

	unsigned int interval;	/* in 100ns units */

	struct mutex mutex;	/* protects frame parameters */



	unsigned int uvc_num_requests;

drivers/usb/gadget/function/uvc_video.c

+5 −2
Original line number Diff line number Diff line
@@ -499,7 +499,7 @@ uvc_video_prep_requests(struct uvc_video *video) 
{

	struct uvc_device *uvc = container_of(video, struct uvc_device, video);

	struct usb_composite_dev *cdev = uvc->func.config->cdev;

	unsigned int interval_duration = video->ep->desc->bInterval * 1250;

	unsigned int interval_duration;

	unsigned int max_req_size, req_size, header_size;

	unsigned int nreq;
@@ -513,8 +513,11 @@ uvc_video_prep_requests(struct uvc_video *video) 
		return;

	}



	interval_duration = 2 << (video->ep->desc->bInterval - 1);

	if (cdev->gadget->speed < USB_SPEED_HIGH)

		interval_duration = video->ep->desc->bInterval * 10000;

		interval_duration *= 10000;

	else

		interval_duration *= 1250;



	nreq = DIV_ROUND_UP(video->interval, interval_duration);