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 X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D31AC432C0 for ; Thu, 21 Nov 2019 13:27:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32D5120898 for ; Thu, 21 Nov 2019 13:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574342849; bh=p8voWrCmt33oQBTtqZwdgQvebcCutW2WuDE8PPkPNi0=; h=Subject:To:From:Date:List-ID:From; b=zSS5cK8r4kt6APSZdc6Www2dB+vjIQHGIUcjpGZo4LBf9PdTOhUgg7Wviso8NCLQU 3FzN2mYPW4lPDrZbzDDTGekUP2PL/uAkLgLwYpZHCKMqRYMASFWYQSfMuik3Sh1iWJ jjh2h/qEGXPGvekrF+ehcFpHV1sEnsF7yfBNPjsk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726358AbfKUN12 (ORCPT ); Thu, 21 Nov 2019 08:27:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:46536 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbfKUN12 (ORCPT ); Thu, 21 Nov 2019 08:27:28 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 457B62075E; Thu, 21 Nov 2019 13:27:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574342847; bh=p8voWrCmt33oQBTtqZwdgQvebcCutW2WuDE8PPkPNi0=; h=Subject:To:From:Date:From; b=LgcqxaGvOlZwLIkVs2HDK/vfVmXd4sdmHqhkibMKia+NETfa4ljV6aRP8BZ9ty4zw ybpqzDIFE2FucJ0otzgzU+zL3tKOARdxPNKtcZAwdiOfqpo0lEr7FcxDHnkBCT97Gf zlefAdz4P85Ydk9nVXgCc2WcMpJ2nGTaI+uoiMTo= Subject: patch "staging: comedi: usbduxfast: usbduxfast_ai_cmdtest rounding error" added to staging-testing To: mail@berndporr.me.uk, abbotti@mev.co.uk, gregkh@linuxfoundation.org, stable@vger.kernel.org From: Date: Thu, 21 Nov 2019 14:27:25 +0100 Message-ID: <157434284519572@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled staging: comedi: usbduxfast: usbduxfast_ai_cmdtest rounding error to my staging git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git in the staging-testing branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will be merged to the staging-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >From 222f7381cf6f1eab2ea3a534cbea0815a2b53326 Mon Sep 17 00:00:00 2001 From: Bernd Porr Date: Mon, 18 Nov 2019 23:07:59 +0000 Subject: staging: comedi: usbduxfast: usbduxfast_ai_cmdtest rounding error The userspace comedilib function 'get_cmd_generic_timed' fills the cmd structure with an informed guess and then calls the function 'usbduxfast_ai_cmdtest' in this driver repeatedly while 'usbduxfast_ai_cmdtest' is modifying the cmd struct until it no longer changes. However, because of rounding errors this never converged because 'steps = (cmd->convert_arg * 30) / 1000' and then back to 'cmd->convert_arg = (steps * 1000) / 30' won't be the same because of rounding errors. 'Steps' should only be converted back to the 'convert_arg' if 'steps' has actually been modified. In addition the case of steps being 0 wasn't checked which is also now done. Signed-off-by: Bernd Porr Cc: # 4.4+ Reviewed-by: Ian Abbott Link: https://lore.kernel.org/r/20191118230759.1727-1-mail@berndporr.me.uk Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/usbduxfast.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/drivers/staging/comedi/drivers/usbduxfast.c b/drivers/staging/comedi/drivers/usbduxfast.c index 04bc488385e6..4af012968cb6 100644 --- a/drivers/staging/comedi/drivers/usbduxfast.c +++ b/drivers/staging/comedi/drivers/usbduxfast.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0+ /* - * Copyright (C) 2004-2014 Bernd Porr, mail@berndporr.me.uk + * Copyright (C) 2004-2019 Bernd Porr, mail@berndporr.me.uk */ /* @@ -8,7 +8,7 @@ * Description: University of Stirling USB DAQ & INCITE Technology Limited * Devices: [ITL] USB-DUX-FAST (usbduxfast) * Author: Bernd Porr - * Updated: 10 Oct 2014 + * Updated: 16 Nov 2019 * Status: stable */ @@ -22,6 +22,7 @@ * * * Revision history: + * 1.0: Fixed a rounding error in usbduxfast_ai_cmdtest * 0.9: Dropping the first data packet which seems to be from the last transfer. * Buffer overflows in the FX2 are handed over to comedi. * 0.92: Dropping now 4 packets. The quad buffer has to be emptied. @@ -350,6 +351,7 @@ static int usbduxfast_ai_cmdtest(struct comedi_device *dev, struct comedi_cmd *cmd) { int err = 0; + int err2 = 0; unsigned int steps; unsigned int arg; @@ -399,11 +401,16 @@ static int usbduxfast_ai_cmdtest(struct comedi_device *dev, */ steps = (cmd->convert_arg * 30) / 1000; if (cmd->chanlist_len != 1) - err |= comedi_check_trigger_arg_min(&steps, - MIN_SAMPLING_PERIOD); - err |= comedi_check_trigger_arg_max(&steps, MAX_SAMPLING_PERIOD); - arg = (steps * 1000) / 30; - err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg); + err2 |= comedi_check_trigger_arg_min(&steps, + MIN_SAMPLING_PERIOD); + else + err2 |= comedi_check_trigger_arg_min(&steps, 1); + err2 |= comedi_check_trigger_arg_max(&steps, MAX_SAMPLING_PERIOD); + if (err2) { + err |= err2; + arg = (steps * 1000) / 30; + err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg); + } if (cmd->stop_src == TRIG_COUNT) err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1); -- 2.24.0