uvideo: limit isochronous transfers to 32 frames
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Authored by seuros on Jul 28 2026, 12:14 AM.

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Reviewers

adrian
bapt

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rGad9cc3f1da14: uvideo: limit isochronous transfers to 32 frames

Summary

Raising UVIDEO_NFRAMES_MAX from 40 to 128 in 3b6f833c95eb improved
throughput on xhci but made every camera on an ehci bus fail to
stream. Integrated webcams became unusable.

Measured on a MacBookPro9,2 with two ehci(4) FaceTime HD cameras and an
xhci(4) Logitech C920:

			  128		 32
  ehci, 12 captures	  0 ok		 12 ok
  xhci 1920x1080	  5 fps		  5 fps
  xhci 1280x720		 10 fps		 10 fps

Fixes: 3b6f833c95eb

Diff Detail

Repository

rG FreeBSD src repository

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Event Timeline

seuros created this revision.Jul 28 2026, 12:14 AM

Herald added a subscriber: imp. · View Herald TranscriptJul 28 2026, 12:14 AM

seuros requested review of this revision.Jul 28 2026, 12:14 AM

Harbormaster completed remote builds in B75199: Diff 182874.Jul 28 2026, 12:14 AM

seuros added a parent revision: D58500: fwcamctl: remove, superseded by the video(4) interface.Jul 28 2026, 12:14 AM

seuros added a child revision: D58502: fwcam: release the IR DMA channel when starting the stream fails.Jul 28 2026, 12:18 AM

bapt accepted this revision.Jul 28 2026, 6:46 PM

bapt removed a subscriber: imp.

This revision is now accepted and ready to land.Jul 28 2026, 6:46 PM

seuros added projects: drivers, USB.Jul 28 2026, 7:34 PM

Closed by commit rGad9cc3f1da14: uvideo: limit isochronous transfers to 32 frames (authored by seuros, committed by adrian). · Explain WhyAug 9 2026, 5:02 PM

This revision was automatically updated to reflect the committed changes.

adrian added a commit: rGad9cc3f1da14: uvideo: limit isochronous transfers to 32 frames.

Revision Contents
Changeset List

Path

Size

sys/

dev/

usb/

video/

uvideo.h

2 lines

Diff 183738

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sys/dev/usb/video/uvideo.h

uvideo: limit isochronous transfers to 32 framesClosedPublicActions