Message-ID: <CAFXKEHZ+4OyA4AFPkAayetoK3pWfzf8ubrbozJjcjTqTAnHqFw@mail.gmail.com>
Date: Wed, 19 Mar 2025 00:08:24 +0100
From: Lothar Rubusch <l.rubusch@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, eraretuya@...il.com
Subject: Re: [PATCH v4 05/14] iio: accel: adxl345: add single tap feature

On Sun, Mar 16, 2025 at 12:22 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Thu, 13 Mar 2025 16:50:40 +0000
> Lothar Rubusch <l.rubusch@...il.com> wrote:
>
> > Add the single tap feature with a threshold in 62.5mg/LSB points and a
> > scaled duration in us. Keep singletap threshold in regmap cache but
> > the scaled value of duration in us as member variable.
> >
> > Both use IIO channels for individual enable of the x/y/z axis. Initializes
> > threshold and duration with reasonable content. When an interrupt is
> > caught it will be pushed to the according IIO channel.
> >
>
> > Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
>
> Hi Lothar,
>
> A few things in here are from the discussion that was continuing
> on v3 so I may have said more replying to that.
>
> Anyhow, for now I'll hold off on applying from this point on as
> a few more things to respond to inline.
>
> Jonathan
>
> >
> >  #include "adxl345.h"
> > @@ -31,6 +33,33 @@
> >  #define ADXL345_INT1                 0
> >  #define ADXL345_INT2                 1
> >
> > +#define ADXL345_REG_TAP_AXIS_MSK     GENMASK(2, 0)
> > +
> > +enum adxl345_axis {
> > +     ADXL345_Z_EN = BIT(0),
> > +     ADXL345_Y_EN = BIT(1),
> > +     ADXL345_X_EN = BIT(2),
> > +     /* Suppress double tap detection if value > tap threshold */
> > +     ADXL345_TAP_SUPPRESS = BIT(3),
> > +};
> As per feedback (after you sent this!) on v3, I'd drop
> the last value out of the enum, or just use defines and a u8 for
> the one place this is used for local variable storage.
>
>
> > @@ -198,6 +387,132 @@ static int adxl345_write_raw(struct iio_dev *indio_dev,
> >       return -EINVAL;
> >  }
> >
> > +static int adxl345_read_event_config(struct iio_dev *indio_dev,
> > +                                  const struct iio_chan_spec *chan,
> > +                                  enum iio_event_type type,
> > +                                  enum iio_event_direction dir)
> > +{
> > +     struct adxl345_state *st = iio_priv(indio_dev);
> > +     bool int_en;
> > +     int ret = -EFAULT;
> Not used?
>
> > +
> > +     switch (type) {
> > +     case IIO_EV_TYPE_GESTURE:
> > +             switch (dir) {
> > +             case IIO_EV_DIR_SINGLETAP:
> > +                     ret = adxl345_is_tap_en(st, chan->channel2,
> > +                                             ADXL345_SINGLE_TAP, &int_en);
> > +                     if (ret)
> > +                             return ret;
> > +                     return int_en;
> > +             default:
> > +                     return -EINVAL;
> > +             }
> > +     default:
> > +             return -EINVAL;
> > +     }
> > +}
>
> > +static int adxl345_write_event_value(struct iio_dev *indio_dev,
> > +                                  const struct iio_chan_spec *chan,
> > +                                  enum iio_event_type type,
> > +                                  enum iio_event_direction dir,
> > +                                  enum iio_event_info info,
> > +                                  int val, int val2)
> > +{
> > +     struct adxl345_state *st = iio_priv(indio_dev);
> > +     int ret;
> > +
> > +     ret = adxl345_set_measure_en(st, false);
> > +     if (ret)
> > +             return ret;
> > +
> So in my brief reply to the v3 discussion I suggested perhaps
> factoring out everything from here...
> > +     switch (type) {
> > +     case IIO_EV_TYPE_GESTURE:
> > +             switch (info) {
> > +             case IIO_EV_INFO_VALUE:
> > +                     ret = regmap_write(st->regmap, ADXL345_REG_THRESH_TAP,
> > +                                        min(val, 0xFF));
> > +                     break;
> > +             case IIO_EV_INFO_TIMEOUT:
> > +                     ret = adxl345_set_tap_duration(st, val, val2);
> > +                     break;
> > +             default:
> > +                     ret = -EINVAL;
> > +                     break;
> > +             }
> > +             break;
> > +     default:
> > +             ret = -EINVAL;
> > +             break;
> > +     }
> to here, so as to allow simple direct returns.
>
> I think that will make the code more readable given the need to reenable
> measurements and that you want to leave it off on error.
>

Sorry for replying again on this topic. Pls, find my solution in v5.

After some thinking, I implemented it now using returns directly leaving the
measurement on/off as is. I'm unsure if it actually makes sense, after an error
here to turn measurement on again? I can imagine a situation where a wrong
input might result in an error. Nothing is changed, and measurement
could/should continue. Now, it will probably stop, in case of wrong
input. But is
wrong input actually an issue here?

As other alternative, I can think of is to shift measurement on/off
into the called
functions directly. I think, this approach was used also in the
ADXL380 and seems
to be common. Let me know what you think.

> > +
> > +     if (ret)
> > +             return ret; /* measurement stays off */
> > +
> > +     return adxl345_set_measure_en(st, true);
> > +}
>

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