Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751177AbdCQJda (ORCPT ); Fri, 17 Mar 2017 05:33:30 -0400 Received: from mail-it0-f66.google.com ([209.85.214.66]:35878 "EHLO mail-it0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbdCQJd2 (ORCPT ); Fri, 17 Mar 2017 05:33:28 -0400 MIME-Version: 1.0 In-Reply-To: <6e55c61d-7587-4191-1fc5-de43e26986d7@metafoo.de> References: <20170312133250.GA7772@singhal-Inspiron-5558> <6e55c61d-7587-4191-1fc5-de43e26986d7@metafoo.de> From: Gargi Sharma Date: Fri, 17 Mar 2017 15:02:56 +0530 Message-ID: Subject: Re: [Outreachy kernel] Re: [PATCH] staging: iio: ade7753: replace mlock with driver private lock To: Lars-Peter Clausen Cc: simran singhal , 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 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3132 Lines: 84 On Mon, Mar 13, 2017 at 5:30 PM, Lars-Peter Clausen wrote: > > 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. There are other read/write functions for example, ade7753_spi_{read/write}_reg_8 that use the mutex as well. Should a variant of these functions be introduced as well? Also, how does one go about implementing RMW inside 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. Am I right in understanding that we want to introduce mutex lock for writes in other drivers as well? Thanks, Gargi > > > **/ > > 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; > > } > > > > --