Re: [PATCH v1 09/12] iio: accel: adxl313: add activity sensing

[Lothar Rubusch <l.rubusch@gmail.com>]

Hi Andy, also here I copied from the MARC mailing list.. some questions below.

> List:       linux-iio
> Subject:    Re: [PATCH v1 09/12] iio: accel: adxl313: add activity sensing
> From:       Andy Shevchenko <andy () kernel ! org>
> Date:       2025-05-19 12:15:17
> Message-ID: aCsg1XddkT6sGjev () smile ! fi ! intel ! com
> [Download RAW message or body]
>
> On Sun, May 18, 2025 at 11:13:18AM +0000, Lothar Rubusch wrote:
> > Add possibilities to set a threshold for activity sensing. Extend the
> > interrupt handler to process activity interrupts. Provide functions to set
> > the activity threshold and to enable/disable activity sensing. Further add
> > a fake channel for having x, y and z axis anded on the iio channel.
> >
> > This is a preparatory patch. Some of the definitions and functions are
> > supposed to be extended for inactivity later on.
>
> ...
>
> > +static int adxl313_is_act_inact_en(struct adxl313_data *data,
> > +                              enum adxl313_activity_type type,
> > +                              bool *en)
> > +{
> > +   unsigned int axis_ctrl;
> > +   unsigned int regval;
> > +   int ret;
>
> > +   *en = false;
>
> Even in case of an error? The rule of thumb is to avoid assigning output when
> we know that the error will be returned to the caller.
>
> > +   ret = regmap_read(data->regmap, ADXL313_REG_ACT_INACT_CTL, &axis_ctrl);
> > +   if (ret)
> > +           return ret;
>
> > +   if (type == ADXL313_ACTIVITY)
> > +           *en = FIELD_GET(ADXL313_ACT_XYZ_EN, axis_ctrl);
> > +
> > +   if (*en) {
>
> This doesn't need to re-write the value of *en. Just declare local boolean
> temporary variable and use it and only assign it on success.
>
> > +           ret = regmap_read(data->regmap, ADXL313_REG_INT_ENABLE, &regval);
> > +           if (ret)
> > +                   return ret;
> > +
> > +           *en = adxl313_act_int_reg[type] & regval;
> > +   }
> > +
> > +   return 0;
> > +}
>
> ...
>
> > +static int adxl313_set_act_inact_en(struct adxl313_data *data,
> > +                               enum adxl313_activity_type type,
> > +                               bool cmd_en)
> > +{
> > +   unsigned int axis_ctrl = 0;
> > +   unsigned int threshold;
> > +   bool en;
> > +   int ret;
> > +
> > +   if (type == ADXL313_ACTIVITY)
> > +           axis_ctrl = ADXL313_ACT_XYZ_EN;
> > +
> > +   ret = regmap_update_bits(data->regmap,
> > +                            ADXL313_REG_ACT_INACT_CTL,
> > +                            axis_ctrl,
> > +                            cmd_en ? 0xff : 0x00);
> > +   if (ret)
> > +           return ret;
> > +
> > +   ret = regmap_read(data->regmap, adxl313_act_thresh_reg[type], &threshold);
> > +   if (ret)
> > +           return ret;
>
> > +   en = false;
>
> Instead...
>
> > +   if (type == ADXL313_ACTIVITY)
> > +           en = cmd_en && threshold;
>
>       else
>               en = false;
>
> > +   return regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
> > +                             adxl313_act_int_reg[type],
> > +                             en ? adxl313_act_int_reg[type] : 0);
> > +}
>
> ...

The above is a good example for the following. From time to time, I
face the situation in a
function where I'd like to end up with something like

    if (foo = A) {
        var = thenDoA();
    } else {
        var = thenDoB();
    }
    doSomething(var);

In a first patch I'll introduce only the following and remark in the
commit message, that this will be extended. Since smatch/sparse tool
will complain, I'll need to fiddle around with initializations
(becoming obsolete in the end), e.g. I'll end up with something like
this in a first patch A:

    var = nonsense;
    if (foo = A) {
        var = thenDoA();
    }
    doSomething(var);

This is the case for switch(type) case IIO_...MAG: as only type (for
now). This is the case for this is_act_inact_enabled(),
set_act_inact(), etc.

I assume it's better to simplify each commit individually and don't
leave the "churn" around which might make sense in combination with a
follow patch? Is this a general approach I should follow?

Or, can it be legitimate to just split an if/else and add if-clause in
a patch A and the else clause in the other patch B, since both are
probably actually not complex. Such that patch A for itself looks a
bit odd, but will make sense together with patch B?


> > +static int adxl313_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 adxl313_data *data = iio_priv(indio_dev);
>
> > +   bool int_en;
>
> Why? You return the int here... I would expect rather to see unsigned int...
>
> > +   int ret;
> > +
> > +   switch (type) {
> > +   case IIO_EV_TYPE_MAG:
> > +           switch (dir) {
> > +           case IIO_EV_DIR_RISING:
> > +                   ret = adxl313_is_act_inact_en(data,
> > +                                                 ADXL313_ACTIVITY,
> > +                                                 &int_en);
> > +                   if (ret)
> > +                           return ret;
> > +                   return int_en;
>
> ...or even simply
>
>                       return adx1313...(...);
>
> > +           default:
> > +                   return -EINVAL;
> > +           }
> > +   default:
> > +           return -EINVAL;
> > +   }
> > +}
>
> ...

This one here is interesting, to my understanding I followed here e.g.
the approach of the ADXL380 which is supposed to be a quite recent
driver [the _read/write_event_config() there.]

Now, your remark made me think: I'm unsure, can I actually I implement
the following approach here?
- return >0 : true
- return =0 : false
- return <0 : error

It seems to work (unsure about the  error cases, though), but much
cleaner and simpler! I'll send
that in v2, pls let me know if I missunderstood you.

[...]
>
> --
> With Best Regards,
> Andy Shevchenko

Best,
L