From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out-023.synserver.de ([212.40.185.23]:1133 "EHLO smtp-out-023.synserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751702AbbDAPPx (ORCPT ); Wed, 1 Apr 2015 11:15:53 -0400 Message-ID: <551C0B95.9080802@metafoo.de> Date: Wed, 01 Apr 2015 17:15:33 +0200 From: Lars-Peter Clausen MIME-Version: 1.0 To: Daniel Baluta CC: Kuppuswamy Sathyanarayanan , 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> In-Reply-To: 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 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.