From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207Ab3LKB2J (ORCPT ); Tue, 10 Dec 2013 20:28:09 -0500 Received: from mail.active-venture.com ([67.228.131.205]:55741 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751646Ab3LKB2F (ORCPT ); Tue, 10 Dec 2013 20:28:05 -0500 X-Originating-IP: 108.223.40.66 Message-ID: <52A7BFA4.2080402@roeck-us.net> Date: Tue, 10 Dec 2013 17:28:04 -0800 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: =?UTF-8?B?Sm9zw6kgTWlndWVsIEdvbsOnYWx2ZXM=?= , Jean Delvare , Guenter Roeck , lm-sensors@lm-sensors.org, linux-kernel@vger.kernel.org Subject: Re: [lm-sensors] [PATCH] hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS_QUICK References: <1386723462-21388-1-git-send-email-jose.goncalves@inov.pt> In-Reply-To: <1386723462-21388-1-git-send-email-jose.goncalves@inov.pt> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/10/2013 04:57 PM, José Miguel Gonçalves wrote: > Some I2C bus drivers do not allow zero-lenght data transfers which are s/lenght/length/ > required to start a mesurement with the HIH6130/1 sensor. Nevertheless, s/mesurement/measurement/ > we can overcome this limitation by writing a zero dummy byte. This byte > is ignored by the sensor and was verified to be working with the OMAP > I2C bus driver in a BeagleBone board. > > Signed-off-by: José Miguel Gonçalves > --- > drivers/hwmon/hih6130.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwmon/hih6130.c b/drivers/hwmon/hih6130.c > index 2dc37c7..a860cc4 100644 > --- a/drivers/hwmon/hih6130.c > +++ b/drivers/hwmon/hih6130.c > @@ -121,8 +121,20 @@ static int hih6130_update_measurements(struct i2c_client *client) > */ > if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { > > - /* write to slave address, no data, to request a measurement */ > - ret = i2c_master_send(client, tmp, 0); > + /* > + * Write to slave address, to request a measurement. s/,// > + * According with the datasheet it should be with no data, but > + * for systems with I2C bus drivers that do not allow zero > + * length packets we write one dummy byte to allow sensor > + * measurements on them. > + */ > + if (i2c_get_functionality(client->adapter) & > + I2C_FUNC_SMBUS_QUICK) { > + ret = i2c_master_send(client, tmp, 0); > + } else { > + tmp[0] = 0; > + ret = i2c_master_send(client, tmp, 1); > + } You can simplify this code by introducing a variable to hold the write length into struct hih6130. This variable can be initialized with 1 or 0 in the probe function. if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK)) hih6130->write_length = 0; else hih6130->write_length = 1; Then replace above code with tmp[0] = 0; ret = i2c_master_send(client, tmp, hih6130->write_length); This way you don't have to call i2c_{get,check}_functionality() repeatedly. Thanks, Guenter > if (ret < 0) > goto out; > >