From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <551C2F63.50609@metafoo.de> Date: Wed, 01 Apr 2015 19:48:19 +0200 From: Lars-Peter Clausen MIME-Version: 1.0 To: sathyanarayanan.kuppuswamy@linux.intel.com, 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> <551C2EC4.1050208@linux.intel.com> In-Reply-To: <551C2EC4.1050208@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed List-ID: On 04/01/2015 07:45 PM, sathyanarayanan kuppuswamy wrote: > > > 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. Wait. It needs to cross the threshold or it needs to stay above the threshold?