Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbdCSSJZ (ORCPT ); Sun, 19 Mar 2017 14:09:25 -0400 Received: from mail-it0-f65.google.com ([209.85.214.65]:36499 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254AbdCSSJX (ORCPT ); Sun, 19 Mar 2017 14:09:23 -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: Sun, 19 Mar 2017 23:32:43 +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: 3537 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. > The only instance I was able to find was drivers/iio/adc/vf610_adc.c where read modify write cycles are present on the register VF610_REG_ADC_CFG. I believe writel() & readl() is used for this purpose. In this case, we want to write to data to a device on the SPI bus. Can we use writel() for this purpose? > 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; >> } >> > > -- > You received this message because you are subscribed to the Google Groups "outreachy-kernel" group. > To unsubscribe from this group and stop receiving emails from it, send an email to outreachy-kernel+unsubscribe@googlegroups.com. > To post to this group, send email to outreachy-kernel@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/outreachy-kernel/6e55c61d-7587-4191-1fc5-de43e26986d7%40metafoo.de. > For more options, visit https://groups.google.com/d/optout.