From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailhost.informatik.uni-hamburg.de ([134.100.9.70]:49806 "EHLO mailhost.informatik.uni-hamburg.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750909Ab1LULXH (ORCPT ); Wed, 21 Dec 2011 06:23:07 -0500 Message-ID: <4EF1C18D.5090300@metafoo.de> Date: Wed, 21 Dec 2011 12:22:53 +0100 From: Lars-Peter Clausen MIME-Version: 1.0 To: Duss Pirmin CC: linux-iio@vger.kernel.org Subject: Re: [PATCH] Add support for ads1110 References: <4EE9FB74.6010402@flytec.ch> <4EEA1B54.5060607@metafoo.de> <4EF03E28.4020900@flytec.ch> In-Reply-To: <4EF03E28.4020900@flytec.ch> Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 12/20/2011 08:50 AM, Duss Pirmin wrote: > Hi > > On 12/15/2011 05:07 PM, Lars-Peter Clausen wrote: > >>> +static struct ads1110_conversion_mode >>> +ads1110_conv_mode_table[ADS1110_MAX_CONV_MODE] = { >>> + { "continuous-conversion", 0 }, >>> + { "single-conversion", 1 }, >>> +}; >> >> This should probably not user controllable. You probably want to do a >> single >> conversion when reading from sysfs and use continuous conversion when >> using >> a triggered buffer. > > As this chip doesn't have an interrupt line all we can do is poll to > determine if a conversion is completed. my suggestion here is to just > use continuous conversion and return the last value from the chip. > Otherwise we would need to poll in the read routine for sysfs. Or is > there a better way to do it? > I would assume that the downside of having the chip constantly performing conversions is that power consumption increases. If you know how long approximately a conversion takes you could start the conversion in single mode wait the conversion time and read the result back. >>> +static struct attribute *ads1110_attributes[] = { >>> +&iio_dev_attr_available_conversion_modes.dev_attr.attr, >>> +&iio_dev_attr_available_data_rates.dev_attr.attr, >>> +&iio_dev_attr_available_gains.dev_attr.attr, >>> +&iio_dev_attr_value.dev_attr.attr, >>> +&iio_dev_attr_conversion_mode.dev_attr.attr, >>> +&iio_dev_attr_data_rate.dev_attr.attr, >>> +&iio_dev_attr_gain.dev_attr.attr, >>> +&iio_dev_attr_start_conversion.dev_attr.attr, >>> + NULL, >>> +}; >> >> Please use channel_spec. Most of the attributes can probably be expresses >> through it. For those which can not please take a look at >> Documentation/sysfs-bus-iio and see which already existing attribute >> names >> match your use case. E.g. your "data_rate" should probably be >> "sampling_frequency". >> > > Is there an attribute for gain? I'm asking this, because the next chip I > will write a driver for is the TI ADS1242, which also has a programmable > gain. We usually make the scale attribute writable for changing the gain. And if the gain factor can only be on of a few discrete values also provide scale_available attribute.