Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752942AbdCMMBK (ORCPT ); Mon, 13 Mar 2017 08:01:10 -0400 Received: from www381.your-server.de ([78.46.137.84]:59803 "EHLO www381.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752891AbdCMMA7 (ORCPT ); Mon, 13 Mar 2017 08:00:59 -0400 Subject: Re: [PATCH] staging: iio: ade7753: replace mlock with driver private lock To: simran singhal References: <20170312133250.GA7772@singhal-Inspiron-5558> Cc: Michael Hennerich , Jonathan Cameron , Hartmut Knaack , Pete Meerwald-Stadler , Greg Kroah-Hartman , linux-iio@vger.kernel.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, outreachy-kernel@googlegroups.com From: Lars-Peter Clausen Message-ID: <6e55c61d-7587-4191-1fc5-de43e26986d7@metafoo.de> Date: Mon, 13 Mar 2017 13:00:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.6.0 MIME-Version: 1.0 In-Reply-To: <20170312133250.GA7772@singhal-Inspiron-5558> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: lars@metafoo.de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2434 Lines: 67 On 03/12/2017 02:32 PM, simran singhal wrote: > The IIO subsystem is redefining iio_dev->mlock to be used by > the IIO core only for protecting device operating mode changes. > ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes. > > In this driver, mlock was being used to protect hardware state > changes. Replace it with a lock in the devices global data. > > Fix some coding style issues related to white space also. > > Signed-off-by: simran singhal > --- > drivers/staging/iio/meter/ade7753.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/staging/iio/meter/ade7753.c b/drivers/staging/iio/meter/ade7753.c > index dfd8b71..ca99d82 100644 > --- a/drivers/staging/iio/meter/ade7753.c > +++ b/drivers/staging/iio/meter/ade7753.c > @@ -81,12 +81,14 @@ > * @tx: transmit buffer > * @rx: receive buffer > * @buf_lock: mutex to protect tx and rx > + * @lock: protect sensor state It might make sense to reuse the existing lock which currently protects the read/write functions. You can do this by introducing a variant of ade7753_spi_{read,write}_reg_16() that does not take a lock and use these to implement the read-modify-write cycle in a protected section. Looking through the driver there seem to be other places as well that do read-modify-write that should be protected by a lock, but currently are not. This might be a good task. > **/ > struct ade7753_state { > - struct spi_device *us; > - struct mutex buf_lock; > - u8 tx[ADE7753_MAX_TX] ____cacheline_aligned; > - u8 rx[ADE7753_MAX_RX]; > + struct spi_device *us; > + struct mutex buf_lock; > + struct mutex lock; /* protect sensor state */ > + u8 tx[ADE7753_MAX_TX] ____cacheline_aligned; > + u8 rx[ADE7753_MAX_RX]; > }; > > static int ade7753_spi_write_reg_8(struct device *dev, > @@ -484,7 +486,7 @@ static ssize_t ade7753_write_frequency(struct device *dev, > if (!val) > return -EINVAL; > > - mutex_lock(&indio_dev->mlock); > + mutex_lock(&st->lock); > > t = 27900 / val; > if (t > 0) > @@ -505,7 +507,7 @@ static ssize_t ade7753_write_frequency(struct device *dev, > ret = ade7753_spi_write_reg_16(dev, ADE7753_MODE, reg); > > out: > - mutex_unlock(&indio_dev->mlock); > + mutex_unlock(&st->lock); > > return ret ? ret : len; > } >