Comments inline.
On 04/09/2015 03:16 AM, Jonathan Cameron wrote:
On 01/04/15 20:22, sathyanarayanan kuppuswamy wrote:
On 04/01/2015 12:06 PM, sathyanarayanan kuppuswamy wrote:
On 04/01/2015 10:48 AM, Lars-Peter Clausen wrote:
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 <lars@xxxxxxxxxx> 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?
Following is the logic for this chip.
If ( data > Upper_threshold or data < Lower_threshold)
generate_event()
Missed to add <n> times logic
If ( data > Upper_threshold or data < Lower_threshold) {
increment_count;
if (count >= n) {
generate_event()
reset_count()
}
}
So level rather than edge triggered. Definitely what we put _period
in for in the first place. Admittedly persistence might have been a better
name, but too late now! (dratted ABI compatibility)
J
But we cannot use period for this use case. According to _period ABI
description,
It specifies the period of time for which the condition must be true for
getting a
valid event. But here, we are checking for number of times a condition
must be
true for generating a valid event.
Description:
Period of time (in seconds) for which the condition must be
met before an event is generated. If direction is not
specified then this period applies to both directions.
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--
Sathyanarayanan Kuppuswamy
Android kernel developer
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