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Date:   Sun, 14 Aug 2022 18:04:51 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Jagath Jog J <jagathjog1996@gmail.com>
Cc:     andy.shevchenko@gmail.com, hadess@hadess.net, hdegoede@redhat.com,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] iio: Add new event type gesture and use
 direction for single and double tap
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In-Reply-To: <20220813071803.4692-2-jagathjog1996@gmail.com>
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        <20220813071803.4692-2-jagathjog1996@gmail.com>
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On Sat, 13 Aug 2022 12:48:02 +0530
Jagath Jog J <jagathjog1996@gmail.com> wrote:

> Add new event type for tap called gesture and the direction can be used
> to differentiate single and double tap. This may be used by accelerometer
> sensors to express single and double tap events. For directional tap,
> modifiers like IIO_MOD_(X/Y/Z) can be used along with singletap and
> doubletap direction.
> 
> Signed-off-by: Jagath Jog J <jagathjog1996@gmail.com>
Hi Jagath,

This ABI is definitely something I want more eyes than ours on, so
whatever happens I'll leave it on the list for a few weeks.

> ---
>  Documentation/ABI/testing/sysfs-bus-iio | 41 +++++++++++++++++++++++++
>  drivers/iio/industrialio-event.c        |  7 ++++-
>  include/linux/iio/types.h               |  2 ++
>  include/uapi/linux/iio/types.h          |  3 ++
>  tools/iio/iio_event_monitor.c           |  8 ++++-
>  5 files changed, 59 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index e81ba6f5e1c8..54cb925f714c 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -2038,3 +2038,44 @@ Description:
>  		Available range for the forced calibration value, expressed as:
>  
>  		- a range specified as "[min step max]"
> +
> +What:		/sys/.../events/in_accel_gesture_singletap_en
> +What:		/sys/.../events/in_accel_gesture_doubletap_en
> +KernelVersion:	5.21
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Device generates an event on a single or double tap.
> +
> +What:		/sys/.../events/in_accel_gesture_singletap_value
> +What:		/sys/.../events/in_accel_gesture_doubletap_value
> +KernelVersion:	5.21
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Specifies the threshold value that the device is comparing
> +		against to generate the tap gesture event. Units and exact
> +		meaning of value are device specific.

I wonder if we should list a direction?  As in smaller is more sensitive?
(at least to first approximation)
That way a user would at least be able to consistently decide if they should
raise or lower the number to get the perf the want.

> +
> +What:		/sys/.../events/in_accel_gesture_singletap_reset_timeout
> +What:		/sys/.../events/in_accel_gesture_doubletap_reset_timeout
> +KernelVersion:	5.21
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Specifies the timeout value in seconds for the tap detector
> +		to not to look for another tap event after the event as
> +		occoured. Basically the minimum quiet time between the two
spelling.  occured

> +		single-tap's or two double-tap's.
> +
> +What:		/sys/.../events/in_accel_gesture_doubletap_tap_2min_delay

I'm not sure this naming is intuitive enough. Might be a simple
as doubletap_tap2_min_delay?  My brain didn't parse 2min correctly.

This one is a bit odd, so definitely want to hear more view points on whether
this is general enough to cover sensors and intuitive enough that people
have some hope of setting it right.

> +KernelVersion:	5.21
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Specifies the minimum quiet time in seconds between the two
> +		taps of a double tap.
> +
> +What:		/sys/.../events/in_accel_gesture_maxtomin_time
> +KernelVersion:	5.21
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Specifies the maximum time difference allowed between upper
> +		and lower peak of tap to consider it as the valid tap event.
> +		Units in seconds.
Needs to be associated with 'tap' in the naming.
Easiest is probably only to define it as
singletap_maxtomin_time + doubletap_maxtomin_time and not have the
shared version as we'd lose the 'tap' part of the name.