From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5753133B6EA for ; Wed, 5 Nov 2025 15:47:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762357634; cv=none; b=k2OfJNdnW8USQMIZdrownJsvNC+Mw5bRRgH+TOvXT/I554NXzW+vlGkjvmAepO0l7iXiwHBbGHiuxxrxO5vtbI2B5o/zZBYZtCMoSXVV7kpvkh20H317TMka7cCswgWeFbjOJEHycqGej8fskYd8MNl5PKzi1PeEmeVjVcZmu3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762357634; c=relaxed/simple; bh=1Bu5YshwY9av4y8fRIuWg/0uAsWTBMqa0fw+NQBpSsU=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=Mr964OZswvbAFVzp/dCpj0jDlyMBmbciMUd28rfVx8J7yoDW2dwqp74A4DLCCFlpKj8rD1EzNXBsrsvwJkPvm+/nIqLxeK3j4mVyPVpx/9IQwLBO3HcsBfKHzyOVNKPj32/OQoooytk8sXrAcG+KQvAPEVUb3vrttLnQKcPTfII= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Fl49wY30; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Fl49wY30" Received: by smtp.kernel.org (Postfix) with ESMTPS id CEF5FC19424 for ; Wed, 5 Nov 2025 15:47:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762357633; bh=1Bu5YshwY9av4y8fRIuWg/0uAsWTBMqa0fw+NQBpSsU=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Fl49wY309GS1poyEV7Da7iwKDZYpp4//yr8rxhu3OajmQLPLkUEz63fuOcqmfEcrX con7L0JuKoA969j9Wse+rMGGw1AVRs2V1PwE0Vzopfm9FmMXSI4zFQcWy9bCIPsj4q wx59CuO+gJYUGjJVOO8H7phmfRHvJ1a9oXvmldj4QAndE+gp4zowbSWLp+oKH3emp3 F5ebS2WZvl11Gm3wnfbdzacFo6Ng4da81Wy1C8MGlONn7tg1EO65aqrc1wHgmJdVtH gKTNnSfkHIHLfm6avTYQLsSn0IjKwB86sf9oFa/xJsmYwCQXtCgiLCoNn+zhUOT5f2 M1pNxSbK48RhQ== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id C9927C433E1; Wed, 5 Nov 2025 15:47:13 +0000 (UTC) From: bugzilla-daemon@kernel.org To: linux-usb@vger.kernel.org Subject: [Bug 220748] usb: xhci_queue_isoc_tx_prepare ignore start_frame and always assumes URB_ISO_ASAP is set Date: Wed, 05 Nov 2025 15:47:13 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo drivers_usb@kernel-bugs.kernel.org X-Bugzilla-Product: Drivers X-Bugzilla-Component: USB X-Bugzilla-Version: 2.5 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: stern@rowland.harvard.edu X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: drivers_usb@kernel-bugs.kernel.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 https://bugzilla.kernel.org/show_bug.cgi?id=3D220748 --- Comment #5 from Alan Stern (stern@rowland.harvard.edu) --- For anyone who wants to know more about how isochronous scheduling is inten= ded to work in the Linux USB stack, see the description in the kerneldoc for usb_submit_urb() in drivers/usb/core/urb.c. In short, the start_frame field in struct urb is output-only. The host controller driver doesn't pay any attention to it when an URB is submitted,= but the frame assigned to the URB's first isochronous packet gets stored in start_frame before the URB completes. Furthermore, the URB_ISO_ASAP flag o= nly affects what happens to an URB that was submitted too late to keep the endpoint's queue going (say, because interrupts were blocked for too long).= If the queue is just starting up, or the URB isn't already too late, URB_ISO_A= SAP is ignored. Also, host controller drivers are not likely to pay attention to the interv= al field. They will use the interval specified in the endpoint's descriptor. --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=