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Date:   Sun, 4 Sep 2022 16:58:23 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Crt Mori <cmo@melexis.com>
Cc:     linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2 2/3] iio: temperature: mlx90632 Read sampling
 frequency
Message-ID: <20220904165823.4388b699@jic23-huawei>
In-Reply-To: <CAKv63uuHpjVEPoTgcJ6QptQmkCmvWhh8eNBwibOrR0SQGLG8Bg@mail.gmail.com>
References: <20220903222402.3426058-1-cmo@melexis.com>
        <20220904154535.0bb526bc@jic23-huawei>
        <CAKv63uuHpjVEPoTgcJ6QptQmkCmvWhh8eNBwibOrR0SQGLG8Bg@mail.gmail.com>
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On Sun, 4 Sep 2022 17:23:16 +0200
Crt Mori <cmo@melexis.com> wrote:

> On Sun, 4 Sept 2022 at 17:19, Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > On Sun,  4 Sep 2022 00:24:02 +0200
> > cmo@melexis.com wrote:
> >  
> > > From: Crt Mori <cmo@melexis.com>
> > >
> > > Allow users to read sensor sampling frequency to better plan the
> > > application measurement requests.  
> >
> > I didn't read this closely enough.  Why is the frequency read only?
> > We'd not normally have an available attribute in that case, because
> > the values aren't available if we have no way to set the value.
> >  
> 
> It is writable, but so far I did not want to include the change part,
> because it is writing to EEPROM and that means sensor slowly gets
> killed as memory has limited number of write cycles.

Ah. One of those.  Please add some comments to make that clear
+ I think the available part should wait for any patch that adds
support for writing.  We may want to gate that write in some fashion
- perhaps with some non standard ABI so normal code can't do it.

Jonathan

> 
> > Jonathan
> >  
> > >
> > > Signed-off-by: Crt Mori <cmo@melexis.com>
> > > ---
> > >  drivers/iio/temperature/mlx90632.c | 44 ++++++++++++++++++++++++++++++
> > >  1 file changed, 44 insertions(+)
> > >
> > > diff --git a/drivers/iio/temperature/mlx90632.c b/drivers/iio/temperature/mlx90632.c
> > > index 9acd819c76a6..37edd324d6a1 100644
> > > --- a/drivers/iio/temperature/mlx90632.c
> > > +++ b/drivers/iio/temperature/mlx90632.c
> > > @@ -80,6 +80,9 @@
> > >  #define MLX90632_PWR_STATUS_CONTINUOUS MLX90632_PWR_STATUS(3) /* continuous */
> > >
> > >  #define MLX90632_EE_RR(ee_val) (ee_val & GENMASK(10, 8)) /* Only Refresh Rate bits */
> > > +#define MLX90632_REFRESH_RATE(ee_val) (MLX90632_EE_RR(ee_val) >> 8)
> > > +                                     /* Extract Refresh Rate from ee register */
> > > +#define MLX90632_REFRESH_RATE_STATUS(refresh_rate) (refresh_rate << 8)
> > >
> > >  /* Measurement types */
> > >  #define MLX90632_MTYP_MEDICAL 0
> > > @@ -908,6 +911,24 @@ static int mlx90632_calc_ambient_dsp105(struct mlx90632_data *data, int *val)
> > >       return ret;
> > >  }
> > >
> > > +static int mlx90632_get_refresh_rate(struct mlx90632_data *data,
> > > +                                  int *refresh_rate)
> > > +{
> > > +     unsigned int meas1;
> > > +     int ret;
> > > +
> > > +     ret = regmap_read(data->regmap, MLX90632_EE_MEDICAL_MEAS1, &meas1);
> > > +     if (ret < 0)
> > > +             return ret;
> > > +
> > > +     *refresh_rate = MLX90632_REFRESH_RATE(meas1);
> > > +
> > > +     return ret;
> > > +}
> > > +
> > > +static const int mlx90632_freqs[][2] = { {0, 500000}, {1, 0}, {2, 0}, {4, 0},
> > > +                                       {8, 0}, {16, 0}, {32, 0}, {64, 0} };
> > > +
> > >  static int mlx90632_pm_interraction_wakeup(struct mlx90632_data *data)
> > >  {
> > >       unsigned long now;
> > > @@ -978,6 +999,15 @@ static int mlx90632_read_raw(struct iio_dev *indio_dev,
> > >               *val = data->object_ambient_temperature;
> > >               ret = IIO_VAL_INT;
> > >               break;
> > > +     case IIO_CHAN_INFO_SAMP_FREQ:
> > > +             ret = mlx90632_get_refresh_rate(data, &cr);
> > > +             if (ret < 0)
> > > +                     goto mlx90632_read_raw_pm;
> > > +
> > > +             *val = mlx90632_freqs[cr][0];
> > > +             *val2 = mlx90632_freqs[cr][1];
> > > +             ret = IIO_VAL_INT_PLUS_MICRO;
> > > +             break;
> > >       default:
> > >               ret = -EINVAL;
> > >               break;
> > > @@ -1012,12 +1042,24 @@ static int mlx90632_write_raw(struct iio_dev *indio_dev,
> > >       }
> > >  }
> > >
> > > +static IIO_CONST_ATTR(sampling_frequency_available, "0.5 1 2 4 8 16 32 64");
> > > +
> > > +static struct attribute *mlx90632_attributes[] = {
> > > +     &iio_const_attr_sampling_frequency_available.dev_attr.attr,
> > > +     NULL
> > > +};
> > > +
> > > +static const struct attribute_group mlx90632_attribute_group = {
> > > +     .attrs = mlx90632_attributes,
> > > +};
> > > +
> > >  static const struct iio_chan_spec mlx90632_channels[] = {
> > >       {
> > >               .type = IIO_TEMP,
> > >               .modified = 1,
> > >               .channel2 = IIO_MOD_TEMP_AMBIENT,
> > >               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> > > +             .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> > >       },
> > >       {
> > >               .type = IIO_TEMP,
> > > @@ -1025,12 +1067,14 @@ static const struct iio_chan_spec mlx90632_channels[] = {
> > >               .channel2 = IIO_MOD_TEMP_OBJECT,
> > >               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
> > >                       BIT(IIO_CHAN_INFO_CALIBEMISSIVITY) | BIT(IIO_CHAN_INFO_CALIBAMBIENT),
> > > +             .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> > >       },
> > >  };
> > >
> > >  static const struct iio_info mlx90632_info = {
> > >       .read_raw = mlx90632_read_raw,
> > >       .write_raw = mlx90632_write_raw,
> > > +     .attrs = &mlx90632_attribute_group,
> > >  };
> > >
> > >  static int mlx90632_sleep(struct mlx90632_data *data)  
> >