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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: 48dbe73117 ("usb: gadget: uvc: set req_size and n_requests based on the frame interval")
Cc: stable@vger.kernel.org
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Link: https://patch.msgid.link/20260113-uvc-gadget-fix-patch-v2-2-62950ef5bcb5@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xu Yang 2026-01-13 17:53:08 +08:00 committed by Greg Kroah-Hartman
parent 2edc1acb1a
commit 010dc57cb5
2 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/usb/gadget/function/uvc.h
View File

@ -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;

7
drivers/usb/gadget/function/uvc_video.c
View File

@ -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);