From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9AE8AC4167D for ; Mon, 6 Nov 2023 10:42:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229658AbjKFKmo (ORCPT ); Mon, 6 Nov 2023 05:42:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229478AbjKFKml (ORCPT ); Mon, 6 Nov 2023 05:42:41 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 283DF99; Mon, 6 Nov 2023 02:42:39 -0800 (PST) Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 8B3C4672; Mon, 6 Nov 2023 11:42:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1699267337; bh=LhNtk/nSwRZtfXgSWCgSIqPYb/rXuEPu9bAk43W2SCo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VsdZGutabTHrpDQbFGAzG1ovVlFHn/RWjBwSGlx2m32qMwQojlIA1PEIJwQzKF6Cg qSzrfHsDq32zEqfQIsIM3LcYqgK80kblBbPmvVx/DvWBUpNTJ2w8irj3X3JVTjBFfi LnpE5opR/VCindFYTA2TLZqOFBIJJYGOpu6npxMk= Date: Mon, 6 Nov 2023 12:42:45 +0200 From: Laurent Pinchart To: Ricardo Ribalda Cc: Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Esker Wong Subject: Re: [PATCH] media: uvcvideo: Implement V4L2_EVENT_FRAME_SYNC Message-ID: <20231106104245.GB19272@pendragon.ideasonboard.com> References: <20231020-uvc-event-v1-1-3baa0e9f6952@chromium.org> <20231106103925.GA19272@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231106103925.GA19272@pendragon.ideasonboard.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 06, 2023 at 12:39:26PM +0200, Laurent Pinchart wrote: > On Fri, Oct 20, 2023 at 06:41:45AM +0000, Ricardo Ribalda wrote: > > Add support for the frame_sync event, so user-space can become aware > > earlier of new frames. > > > > Suggested-by: Esker Wong > > Tested-by: Esker Wong > > Signed-off-by: Ricardo Ribalda > > --- > > We have measured a latency of around 30msecs between frame sync > > and dqbuf. > > Not surprising, especially for large resolutions. I'm curious though, > what do you use this event for ? > > > --- > > drivers/media/usb/uvc/uvc_v4l2.c | 2 ++ > > drivers/media/usb/uvc/uvc_video.c | 8 +++++++- > > 2 files changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c > > index f4988f03640a..9f3fb5fd2375 100644 > > --- a/drivers/media/usb/uvc/uvc_v4l2.c > > +++ b/drivers/media/usb/uvc/uvc_v4l2.c > > @@ -1352,6 +1352,8 @@ static int uvc_ioctl_subscribe_event(struct v4l2_fh *fh, > > switch (sub->type) { > > case V4L2_EVENT_CTRL: > > return v4l2_event_subscribe(fh, sub, 0, &uvc_ctrl_sub_ev_ops); > > + case V4L2_EVENT_FRAME_SYNC: > > + return v4l2_event_subscribe(fh, sub, 0, NULL); > > default: > > return -EINVAL; > > } > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > index 28dde08ec6c5..1d4b4807b005 100644 > > --- a/drivers/media/usb/uvc/uvc_video.c > > +++ b/drivers/media/usb/uvc/uvc_video.c > > @@ -1073,9 +1073,15 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, > > * that discontinuous sequence numbers always indicate lost frames. > > */ > > if (stream->last_fid != fid) { > > - stream->sequence++; > > + struct v4l2_event event = { > > + .type = V4L2_EVENT_FRAME_SYNC, > > + .u.frame_sync.frame_sequence = ++stream->sequence, > > Extra space before ++. > > It's easy to miss the ++ there when reading the code, would the > following be more readable ? > > struct v4l2_event event = { > .type = V4L2_EVENT_FRAME_SYNC, > }; > > stream->sequence++; > if (stream->sequence) > uvc_video_stats_update(stream); > > .u.frame_sync.frame_sequence = stream->sequence; Obviously this should read event.u.frame_sync.frame_sequence = stream->sequence; > v4l2_event_queue(&stream->vdev, &event); > > > + }; > > + > > if (stream->sequence) > > uvc_video_stats_update(stream); > > + > > + v4l2_event_queue(&stream->vdev, &event); > > } > > > > uvc_video_clock_decode(stream, buf, data, len); > > > > --- > > base-commit: ce55c22ec8b223a90ff3e084d842f73cfba35588 > > change-id: 20231020-uvc-event-d3d1bbbdcb2f -- Regards, Laurent Pinchart