From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B7C9751814C; Tue, 29 Sep 2026 12:34:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790685267; cv=none; b=jS1ybcHH48n/QsNp/h+8ujWg6AFtCmtgmdpISn8MbUC4mGA5eykY7AL63YEdknQPRM/+oJzLBcAyUM75RQQMfTrAPEkL6uFsHj5Ae9A5TN2nkQI8tggk9FfVgA5FnahuOcAr7bvYWbBm/7rnlOkm2/wOQvTvt60OTNPPukvTTJY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790685267; c=relaxed/simple; bh=fCKWi2QDPT1h5kFh3IYMBx7BAmHDa64Q4UYl1zBfbDc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZRN8Nr48lXUYMh5T5tZLX9i462Vqs1QXXOH1KTnp3CBNusCQznvBbwD7bny9pNXnaOCW1PgC7geq68iPvyf+kq+YJXcbxnBUhgWHOuNPAxvGgWOrXueEGfZfScW0EkXfgmCqoS1aNECr0SwYLvLY/I6sJ69JOxt7XIu+8asd6Zo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=awCNgN7n; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="awCNgN7n" Received: from killaraus.ideasonboard.com (2001-14ba-70f3-e800--a06.rev.dnainternet.fi [IPv6:2001:14ba:70f3:e800::a06]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id E17B3C3D; Tue, 29 Sep 2026 14:32:32 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1790685153; bh=fCKWi2QDPT1h5kFh3IYMBx7BAmHDa64Q4UYl1zBfbDc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=awCNgN7nTzR3LJ2HGhsVUMy8Ntxl0V50Y76shdD1n8gEPrBVsd9E/vGX11pP4Roxn A6ILWGewEAvVHb/nQ2iJbwJZ/gLJmMr4JjUAiAZmwUG8DWjohTaJLkoq8kBhtd73kQ tQ+yHlo9M248mvcNp6Qj5bAq7JtovmL1N4Zxtu8U= Date: Tue, 29 Sep 2026 15:34:22 +0300 From: Laurent Pinchart To: Michael Jordan Cc: Hans de Goede , Ricardo Ribalda , Mauro Carvalho Chehab , Hans Verkuil , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Hans de Goede Subject: Re: [PATCH v4 1/4] media: uvcvideo: report AUTO_UPDATE controls as volatile Message-ID: <20260929123422.GA349401@killaraus.ideasonboard.com> References: <20260928215021.819064-1-jordan.mymail@gmail.com> <20260928215021.819064-2-jordan.mymail@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260928215021.819064-2-jordan.mymail@gmail.com> On Mon, Sep 28, 2026 at 05:50:18PM -0400, Michael Jordan wrote: > AUTO_UPDATE controls can change on their own, and the driver already > re-reads them from the device. Tell userspace by setting > V4L2_CTRL_FLAG_VOLATILE, plus EXECUTE_ON_WRITE for writable controls > so that writes are not ignored. Writes are not ignored by the driver regardless of whether or not V4L2_CTRL_FLAG_EXECUTE_ON_WRITE is reported to userspace. > Suggested-by: Ricardo Ribalda > Reviewed-by: Ricardo Ribalda > Reviewed-by: Hans de Goede > Assisted-by: LLM > Signed-off-by: Michael Jordan > --- > drivers/media/usb/uvc/uvc_ctrl.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c > index 3ca108b83f1d..aceb263103e9 100644 > --- a/drivers/media/usb/uvc/uvc_ctrl.c > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > @@ -1840,6 +1840,17 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain, > if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_MAX) && > (ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN)) > v4l2_ctrl->flags |= V4L2_CTRL_FLAG_HAS_WHICH_MIN_MAX; A blank line here would be nice. > + if (ctrl->info.flags & UVC_CTRL_FLAG_AUTO_UPDATE) { > + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_VOLATILE; > + /* > + * Writes to a volatile control are documented to be ignored > + * unless EXECUTE_ON_WRITE is also reported. The driver sends > + * every write of a writable control to the device, so report > + * the flag accordingly. > + */ > + if (ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR) > + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE; > + } The V4L2 documentation also states Setting a new value for a volatile control will never trigger a V4L2_EVENT_CTRL_CH_VALUE event. This patch seems to break that as we unconditionally send V4L2_EVENT_CTRL_CH_VALUE events on control write for controls that don't have UVC_CTRL_FLAG_ASYNCHRONOUS set. > > if (mapping->master_id) > __uvc_find_control(ctrl->entity, mapping->master_id, -- Regards, Laurent Pinchart