From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932777AbbJ1JYY (ORCPT ); Wed, 28 Oct 2015 05:24:24 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:37696 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932551AbbJ1JYE (ORCPT ); Wed, 28 Oct 2015 05:24:04 -0400 Subject: Re: [PATCH v2 1/2] hwmon: ina2xx: convert driver to using regmap To: Guenter Roeck References: <20151027011229.GC31838@roeck-us.net> <1445939468-21755-1-git-send-email-mtitinger@baylibre.com> <20151028024711.GA30927@roeck-us.net> Cc: jdelvare@suse.com, lm-sensors@lm-sensors.org, linux-kernel@vger.kernel.org, mturquette@baylibre.com, bcousson@baylibre.com, ptitiano@baylibre.com From: Marc Titinger Message-ID: <5630942F.1020705@baylibre.com> Date: Wed, 28 Oct 2015 10:23:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20151028024711.GA30927@roeck-us.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/10/2015 03:47, Guenter Roeck wrote: > On Tue, Oct 27, 2015 at 10:51:07AM +0100, Marc Titinger wrote: >> Any sysfs "show" read access from the client app will result in reading >> all registers (8 with ina226). Depending on the host this can limit the >> best achievable read rate. >> >> This changeset allows for individual register accesses through regmap. >> >> Tested with BeagleBone Black (Baylibre-ACME) and ina226. >> >> Signed-off-by: Marc Titinger >> --- >> >> v2: >> - rename 'rv' to 'regval' for clarity >> - fix missed smbus_xxx api change to regmap >> - rename ina2xx_do_update to ina2xx_read_reg >> - fix indentation >> >> drivers/hwmon/ina2xx.c | 211 +++++++++++++++++++------------------------------ >> 1 file changed, 82 insertions(+), 129 deletions(-) >> >> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c >> index 4d28150..5e7ada8 100644 >> --- a/drivers/hwmon/ina2xx.c >> +++ b/drivers/hwmon/ina2xx.c > > [ ... ] >> >> - mutex_lock(&data->update_lock); >> data->rshunt = val; >> status = ina2xx_calibrate(data); >> - mutex_unlock(&data->update_lock); > > I think this can result in a race conditon if multiple processes > try to update the shunt resistor value at the same time in a > multi-core system. There is no guarantee that the value programmed > into the chip matches the value that is written into 'rshunt'. > So I think we still need the mutex, unless you have a better > idea how to avoid the race. > Right, I had that same afterthought when removing the mutex at that position. Fix incoming! M. > Thanks, > Guenter >