From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com ([134.134.136.24]:7391 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752189AbbDARp1 (ORCPT ); Wed, 1 Apr 2015 13:45:27 -0400 Message-ID: <551C2EC4.1050208@linux.intel.com> Date: Wed, 01 Apr 2015 10:45:40 -0700 From: sathyanarayanan kuppuswamy Reply-To: sathyanarayanan.kuppuswamy@linux.intel.com MIME-Version: 1.0 To: Lars-Peter Clausen , Daniel Baluta CC: Jonathan Cameron , Peter Meerwald , "linux-iio@vger.kernel.org" , Srinivas Pandruvada Subject: Re: [PATCH v1 2/3] iio: ltr501: Add interrupt rate control support References: <212b45fac712e84a3cf0bc5955def7d1b683a6bd.1427856701.git.sathyanarayanan.kuppuswamy@linux.intel.com> <551C030E.1090309@metafoo.de> <551C0B95.9080802@metafoo.de> In-Reply-To: <551C0B95.9080802@metafoo.de> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 04/01/2015 08:15 AM, Lars-Peter Clausen wrote: > On 04/01/2015 05:02 PM, Daniel Baluta wrote: >> On Wed, Apr 1, 2015 at 5:39 PM, Lars-Peter Clausen >> wrote: >>> On 04/01/2015 04:04 PM, Daniel Baluta wrote: >>> [...] >>>> >>>> >>>>> +static const struct iio_chan_spec_ext_info ltr501_ext_info[] = { >>>>> + { >>>>> + .name = "intr_persist", >>>>> + .read = ltr501_read_intr_prst, >>>>> + .write = ltr501_write_intr_prst, >>>>> + .shared = IIO_SHARED_BY_TYPE, >>>>> + }, >>>>> + {}, >>>>> +}; >>>>> + >>>> >>>> Would be nice to standardize persistence attribute >>>> (IIO_CHAN_INFO_PERSISTENCE). >>> >>> >>> If I understand the behavior correctly it causes that the event >>> needs to be >>> triggered at least n times before the event is reported by the chip. >>> In my >>> opinion 'persistence' is not a good term for that. I'm not sure what a >>> better term is but I think it should go more in the direction of >>> ratelimit >>> or something. >> >> I've seen this term used for many devices: >> >> * TSL25911 ambient light sensor [1] >> >> [ One set of thresholds can be configured to trigger an interrupt >> only when >> the ambient light exceeds them for a configurable amount of time >> (persistence) >> ] >> >> * TAOS TCS34725 ambient light sensor [2] >> [ >> The interrupt persistence filter allows the user to define the number >> of consecutive >> out-of-threshold events necessary before generating an interrupt. >> ] >> >> * Avago SAPDS-9950, Sensortek STK3310 >> >> I think the TSL25911 datasheet best describes this parameter, as the >> amount of time >> that ambient light should exceed a threshold until an interrupt is >> generated. > > Ok, that makes more sense. I misunderstood the initial description as > that the signal would have to go first above the threshold then below > the threshold, and this for a number of times. Whereas it needs to > exceed the threshold for a certain amount of time before the event is > triggered. If it goes below the threshold before the persistence > interval no event is triggered and the counter is reset. Yes, it needs to cross the threshold n number of times before a event is generated. > > -- Sathyanarayanan Kuppuswamy Android kernel developer