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=-15.5 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 B717BC433F5 for ; Sun, 5 Sep 2021 15:34:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90A1A60F56 for ; Sun, 5 Sep 2021 15:34:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233765AbhIEPfp (ORCPT ); Sun, 5 Sep 2021 11:35:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:40756 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231485AbhIEPfo (ORCPT ); Sun, 5 Sep 2021 11:35:44 -0400 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (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 65BD660F4A; Sun, 5 Sep 2021 15:34:40 +0000 (UTC) Date: Sun, 5 Sep 2021 16:38:04 +0100 From: Jonathan Cameron To: Miquel Raynal Cc: Lars-Peter Clausen , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Petazzoni , Nuno Sa Subject: Re: [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Message-ID: <20210905163804.67fca556@jic23-huawei> In-Reply-To: <20210902211437.503623-12-miquel.raynal@bootlin.com> References: <20210902211437.503623-1-miquel.raynal@bootlin.com> <20210902211437.503623-12-miquel.raynal@bootlin.com> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, 2 Sep 2021 23:14:32 +0200 Miquel Raynal wrote: > When hardware buffers are enabled (the cnvst pin being the trigger), one > should not mess with the device state by requesting a single channel > read. > > There is already a iio_buffer_enabled() check in *_read_single_value() > to merely prevent this situation but the check is inconsistent since > buffers can be enabled after the if clause anyway. Instead, use the core > mutex by calling iio_device_claim/release_direct_mode(). > > Signed-off-by: Miquel Raynal > --- > drivers/iio/adc/max1027.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c > index f4cb5c75604b..57f62ea2d7aa 100644 > --- a/drivers/iio/adc/max1027.c > +++ b/drivers/iio/adc/max1027.c > @@ -296,10 +296,9 @@ static int max1027_read_single_value(struct iio_dev *indio_dev, > int ret; > struct max1027_state *st = iio_priv(indio_dev); > > - if (iio_buffer_enabled(indio_dev)) { > - dev_warn(&indio_dev->dev, "trigger mode already enabled"); > - return -EBUSY; > - } > + ret = iio_device_claim_direct_mode(indio_dev); > + if (ret) > + return ret; > > /* Configure conversion register with the requested chan */ > st->reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel) | > @@ -325,6 +324,8 @@ static int max1027_read_single_value(struct iio_dev *indio_dev, > if (ret < 0) > return ret; Must also be released in error paths. Treat it like a lock (there is one internally) so to avoid permanent deadlock we must release it even if things are going wrong > > + iio_device_release_direct_mode(indio_dev); > + > *val = be16_to_cpu(st->buffer[0]); > > return IIO_VAL_INT;