linux-kernel - Re: [PATCH 1/3] iio: mma8452: add freefall detection for Freescale's accelerometers

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Date:	Tue, 17 Nov 2015 20:24:50 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	Jonathan Cameron <jic23@...nel.org>, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net,
	christoph.muellner@...obroma-systems.com, mfuzzey@...keon.com
CC:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
Subject: Re: [PATCH 1/3] iio: mma8452: add freefall detection for Freescale's
 accelerometers

Am 2015-11-14 um 20:03 schrieb Jonathan Cameron:
> On 14/11/15 18:45, Martin Kepplinger wrote:
>> Am 2015-11-14 um 19:03 schrieb Jonathan Cameron:
>>> On 11/11/15 18:38, Martin Kepplinger wrote:
>>>> This adds freefall event detection to the supported devices. It adds
>>>> the in_accel_x&y&z_mag_falling_en iio event attribute, which activates
>>>> freefall mode.
>>>>
>>>> In freefall mode, the current acceleration values of all activated axis
>>>> are added and if the *sum* falls *under* the threshold specified
>>>> (in_accel_mag_falling_value), the appropriate IIO event code
>>>> is generated.
>>>>
>>>> By enabling freefall mode (in_accel_x&y&z_mag_falling_en)
>>>> all 3 axis are enabled too as this describes a classic freefall
>>>> detection. Of course the user is free to disable one or more directions.
>>>>
>>>> The values of rising and falling versions of various sysfs files are
>>>> shared, which is compliant to the IIO specification.
>>>>
>>>> This is what the sysfs "events" directory for these devices looks
>>>> like after this change:
>>>>
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_period
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_value
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_period
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_value
>>>> -r--r--r--    4096 Oct 23 08:45 in_accel_scale
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_x&y&z_mag_falling_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_x_mag_falling_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_x_mag_rising_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_y_mag_falling_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_y_mag_rising_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_z_mag_falling_en
>>>> -rw-r--r--    4096 Oct 23 08:45 in_accel_z_mag_rising_en
>>>>
>>>> Signed-off-by: Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
>>>> Signed-off-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
>>> Looks pretty good to me (other than obviously the bits Lars already
>>> picked up on!)
>>>
>>> My only real comment was that you could do the rest of the combined
>>> possibilities whilst you are here (if you want to!)  You've
>>> picked the mostly obviously useful one though so maybe leave it
>>> at that.
>>
>> I'm not sure what you mean. There is only in_accel_x&y&z_mag_falling_en
>> documented. So my guess was to have this to enable freefall mode, taking
>> into account the currently enabled falling axis
>> (in_accel_x_mag_falling_en, ...).
> Sure, but the set of modifiers allows for
> in_accel_x&y_mag_falling_* etc and they aren't documented in this particular
> form simply because no driver has used them yet ;)
> 



I don't see how to do it in iio_event_spec only. Could you point me in
the right direction, could well be I overlook something...

I *can* add a channel for freefall purposes, something like:

static const struct iio_chan_spec mma8653_channels[] = {
        MMA8652_CHANNEL(IIO_MOD_X, idx_axis_x, 10),
        MMA8652_CHANNEL(IIO_MOD_Y, idx_axis_y, 10),
        MMA8652_CHANNEL(IIO_MOD_Z, idx_axis_z, 10),
        MMA8652_CHANNEL(IIO_MOD_X_AND_Y_AND_Z, idx_axis_xyz, 10),
        IIO_CHAN_SOFT_TIMESTAMP(idx_timestamp),
};


just as an example, but then of course I get more than just events: In
the device-directory:

in_accel_x&y&z_calibbias
in_accel_x&y&z_raw
in_accel_x_calibbias
in_accel_x_raw
in_accel_y_calibbias
in_accel_y_raw
in_accel_z_calibbias
in_accel_z_raw


calibbias and raw are not (really) available for x&y&z. I could
calculate a "raw" value, but calibbias doesn't make sense here. ...But
again, maybe I'm on the wrong path!!

thanks a lot!

                              martin


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