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

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Message-ID: <5653F3A1.6010905@posteo.de>
Date:	Tue, 24 Nov 2015 06:20:33 +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 2015-11-17 um 20:24 schrieb Martin Kepplinger:
> 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
> 

Would this be the way to go? And just not support the generated file
that don't apply?

thanks,

                             martin
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