From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx1-f41.google.com (mail-yx1-f41.google.com [74.125.224.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3B22234EEF3 for ; Fri, 28 Aug 2026 15:26:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787930765; cv=none; b=o+SgX38hQ/FmrchGQ3CNBMFZMgf7OcG3s0Aw9kyWyOzTOQqYSwKBXyovlrWIW9VkW0A+UlPokwwg/lhzJIyfIXmydrePfYPC88QfkHPMEaoHboQt8wsJoPaqBWNvWRpz6jUOlvrIskt6DAFSIOnXu7RgqjNM2H17HMAlizWHWPY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787930765; c=relaxed/simple; bh=gW+4ygGqzNQ0vb9xxhCKDAwYheLRCq2jrlm1+aBrI8Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OWxssouCY0MjGB6IZWIwgrNAb6bk9T0fiySMsXoJVig2aC7EzT6QO1SJXMurRILMOCacigFr8BMlsFfsEb1xiX+yqd+s3ypqkp7RBwWK8VhGvXkz265e6DTX74JPIMUrSinT6FlVm0GjUkK3ot26y9LRtLiKsjpHObIqtLshCSs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=JkM4R6y/; arc=none smtp.client-ip=74.125.224.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JkM4R6y/" Received: by mail-yx1-f41.google.com with SMTP id 956f58d0204a3-66e4027b6cfso873323d50.3 for ; Fri, 28 Aug 2026 08:26:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1787930762; x=1788535562; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=chm6rlj0DMPuDVYMC+rhuNex9L2iYUVPl3w1NFWhG38=; b=JkM4R6y/7vuf3+GLmXpvnyUZwS1IJKpXPmXDuYrK4w6anIMgbQQApwKGTRMGIOgL9r YPKKBlf/ZlJBDBr6gPu+bbuRi/YdZ6oonHYuND//QcN4AziUPYh5VhW6mMSWkHZlOVe7 psOgZvTUX++gxu7t+XYNAcQyMVXLNyFN4vVLmZlyW8JXPsiz8pz+oB94z3/EJhuBSFiu /sjYXnKTwgvxLtTSn4Vj0TY6zasEAd3QUyu3wx/UZxpYBBpttqrMmFDgZztXnOEWvb7t TxIgS790PbUCa/NynAUdCwlQPI+6z567eDVFFNTZTgJRpbKXM9K9eI3OTjWOjz5UCVsg YfNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787930762; x=1788535562; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=chm6rlj0DMPuDVYMC+rhuNex9L2iYUVPl3w1NFWhG38=; b=B2lQTUDWpkRrrv0mBmc58A3QA0mx/OPFaars1sBOYMHs/MnHqi6SbeHDTpKHhG/1ES N4ofV7MPlo4jnGPWyWjI8/NEA/o8ZwLR69dITpMIWE5dV2Pkf1mAEc7lImwIO5F4dRER Q084FmsAcAPohzrkcFIP82tIqP/BUQfITAn+j/lNHscQVp7p8RcsEaHmNXWgy87sFWKP nFjJjpRR4zNXrS0GFhVUSkQiol1mKy+WgJN1x1fwarafvgPxhMw+PnjwVMuMxcvQXK4H A0vJS+TP9fqSuV9zXqqyaL1vb1t6VWyeZNRdficLdw6qR8QCOxKJhdmSJKZiwwb/+xgC YO/Q== X-Forwarded-Encrypted: i=1; AKwUvBwteZW5PAJGJJ5JDS2Xlz7xjOO7MNnsxmpWKtHQYwIDc4RR1Hyi2CCVicmAF0/1V69EqkJysM7vV69flA==@vger.kernel.org X-Gm-Message-State: AFuF++nAqbbW7BFDopMwUz8wfDvEb6C/sRNafmqdOGDx0DsITpP3C8Ir /DoIlZIdFitC3S01fP9LLUGI/eavgg0B4KNeJ6X7EpEiupg0LprKZmGk X-Gm-Gg: AYBFou1aVPITXoziN6sye3dGOnexpRZEbBUi11h4ilarTjwcita47DO+lRyvlCW3tRd z1f6Xn2amKRFni4AgtBLml5KZpZXpwKQsY7/QYVucSrMmxjz2Od/jf+x9OBUnrB6amoKaEh1WwB 6U5rliYhJSGC4HKBu8qRdHILv65XOgA6YtbdY9ZI6KJBeok9e/+uPYhxpsazI6jxbX+sR/ktCUC 16zuGPqAgVlkgZQZrC0LVs0/ifY2mSXNsXnWu6Y+n0Ck9wu0yaHex0sRfXE/mPIgci/cVgWHLES jn9IHcinUD//uKC7m2AgvDS24VNmbCLqV91xn6eUobUGet4L9OvHHGN++Txj6s/+Zb472IPp9hi VzL6adJFfPzhiMAuhPj0StTT8UMFnZJXOhkfFgbd/pmDga8ROUz/TAsbOBRig0slwTE438E2DXp ZGcfXvWjzSsf/SQrYmsvWb0bAMsVrDIgjP4WUBsnfX+Kntq28Wny2OOfTW2NedaRC1qpmozmwKQ nDQLc4ufp1V6hNrrDiZyojK+b1/t79kGz9Ww6Z81cM= X-Received: by 2002:a05:690e:11c2:b0:66c:8e41:f5dd with SMTP id 956f58d0204a3-66e4c698a3bmr2106100d50.15.1787930762160; Fri, 28 Aug 2026 08:26:02 -0700 (PDT) Received: from llmbox.. ([38.81.85.65]) by smtp.gmail.com with ESMTPSA id 00721157ae682-85e6756e0f3sm8064327b3.43.2026.08.28.08.26.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Aug 2026 08:26:01 -0700 (PDT) From: Michael Jordan To: Laurent Pinchart , Hans de Goede , Ricardo Ribalda Cc: Mauro Carvalho Chehab , Hans Verkuil , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Jordan Subject: [PATCH 1/3] media: uvcvideo: report AUTO_UPDATE controls as volatile Date: Fri, 28 Aug 2026 11:25:55 -0400 Message-ID: <20260828152557.653475-2-jordan.mymail@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260828152557.653475-1-jordan.mymail@gmail.com> References: <20260828152557.653475-1-jordan.mymail@gmail.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A control with UVC_CTRL_FLAG_AUTO_UPDATE is one whose value the device changes on its own: the driver never trusts its cached value for it, re-reading the device on every VIDIOC_G_EXT_CTRLS (the rollback at the end of the ioctl runs uvc_ctrl_commit_entity(), which clears ctrl->loaded for these controls) and re-reading it after each write. That is exactly what V4L2_CTRL_FLAG_VOLATILE describes to userspace, but the driver never reported it, so applications had no way to know that the value they read can change under them and that a fresh read is worth issuing. Report V4L2_CTRL_FLAG_VOLATILE for AUTO_UPDATE controls. The uAPI documents writes to a volatile control as ignored unless V4L2_CTRL_FLAG_EXECUTE_ON_WRITE is also set, and this driver sends every write of a writable control to the device, so report EXECUTE_ON_WRITE alongside it whenever the control is settable. Suggested-by: Ricardo Ribalda 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 3ca108b83..aceb26310 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; + 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; + } if (mapping->master_id) __uvc_find_control(ctrl->entity, mapping->master_id, -- 2.43.0