linux-kernel - Re: [PATCH] iio: light: acpi-als: Add IO_CHAN_INFO

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Message-ID: <CAMHSBOXJArBSUZqNT0gbN0KQqPAttaWgL=BoXy7keV4Ez0VB6w@mail.gmail.com>
Date:   Fri, 21 Oct 2016 09:43:42 -0700
From:   Gwendal Grignou <gwendal@...omium.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH] iio: light: acpi-als: Add IO_CHAN_INFO_OFFSET/SCALE to mask.

On Fri, Oct 21, 2016 at 1:17 AM, Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
> According the ACPI specification (Version 5.0 Errata A) [1], the data
> coming from the sensor represent the ambient light illuminance reading
> expressed in lux. Unfortunately ACPI interface doesn't provide a
> mechanism to calibrate this value, so this raw value can be slightly
> wrong.
>
> This patch adds IIO_CHAN_INFO_OFFSET and IIO_CHAN_INFO_SCALE attributes
> to give the possibiity to the userspace to calculate a calibrated data
> by doing:
>
>  (raw_value + offset) * scale = calibrated_value (in lux)
>
> [1] http://www.acpi.info/DOWNLOADS/ACPI_5_Errata%20A.pdf
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
>  drivers/iio/light/acpi-als.c | 66 ++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 57 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/light/acpi-als.c b/drivers/iio/light/acpi-als.c
> index f0b47c5..a8093ba 100644
> --- a/drivers/iio/light/acpi-als.c
> +++ b/drivers/iio/light/acpi-als.c
> @@ -56,7 +56,9 @@ static const struct iio_chan_spec acpi_als_channels[] = {
>                 },
>                 /* _RAW is here for backward ABI compatibility */
>                 .info_mask_separate     = BIT(IIO_CHAN_INFO_RAW) |
> -                                         BIT(IIO_CHAN_INFO_PROCESSED),
> +                                         BIT(IIO_CHAN_INFO_PROCESSED) |
> +                                         BIT(IIO_CHAN_INFO_SCALE) |
> +                                         BIT(IIO_CHAN_INFO_OFFSET),
>         },
>  };
>
> @@ -76,6 +78,10 @@ struct acpi_als {
>         struct mutex            lock;
>
>         s32                     evt_buffer[ACPI_ALS_EVT_BUFFER_SIZE];
> +
> +       int                     scale;
> +       int                     uscale;
> +       int                     offset;
>  };
>
>  /*
> @@ -154,25 +160,64 @@ static int acpi_als_read_raw(struct iio_dev *indio_dev,
>         s32 temp_val;
>         int ret;
>
> -       if ((mask != IIO_CHAN_INFO_PROCESSED) && (mask != IIO_CHAN_INFO_RAW))
> -               return -EINVAL;
> -
>         /* we support only illumination (_ALI) so far. */
>         if (chan->type != IIO_LIGHT)
>                 return -EINVAL;
>
> -       ret = acpi_als_read_value(als, ACPI_ALS_ILLUMINANCE, &temp_val);
> -       if (ret < 0)
> -               return ret;
> +       switch (mask) {
> +       case IIO_CHAN_INFO_RAW:
> +       case IIO_CHAN_INFO_PROCESSED:
It seems PROCESSED is identical to RAW. Shouldn't we remove this attribute?
> +               ret = acpi_als_read_value(als, ACPI_ALS_ILLUMINANCE, &temp_val);
> +               if (ret < 0)
> +                       return ret;
> +               *val = temp_val;
> +               return IIO_VAL_INT;
> +       case IIO_CHAN_INFO_OFFSET:
> +               mutex_lock(&als->lock);
> +               *val = als->offset;
> +               mutex_unlock(&als->lock);
> +               return IIO_VAL_INT;
> +       case IIO_CHAN_INFO_SCALE:
> +               mutex_lock(&als->lock);
> +               *val = als->scale;
> +               *val2 = als->uscale;
> +               mutex_unlock(&als->lock);
> +               return IIO_VAL_INT_PLUS_MICRO;
> +       default:
> +               return -EINVAL;
> +       }
> +}
>
> -       *val = temp_val;
> +static int acpi_als_write_raw(struct iio_dev *indio_dev,
> +                             struct iio_chan_spec const *chan, int val,
> +                             int val2, long mask)
> +{
> +       struct acpi_als *als = iio_priv(indio_dev);
> +
> +       if (chan->type != IIO_LIGHT)
> +               return -EINVAL;
>
> -       return IIO_VAL_INT;
> +       switch (mask) {
> +       case IIO_CHAN_INFO_OFFSET:
> +               mutex_lock(&als->lock);
> +               als->offset = val;
> +               mutex_unlock(&als->lock);
> +               return 0;
> +       case IIO_CHAN_INFO_SCALE:
> +               mutex_lock(&als->lock);
> +               als->scale = val;
> +               als->uscale = val2;
> +               mutex_unlock(&als->lock);
> +               return 0;
> +       default:
> +               return -EINVAL;
> +       }
>  }
>
>  static const struct iio_info acpi_als_info = {
>         .driver_module          = THIS_MODULE,
>         .read_raw               = acpi_als_read_raw,
> +       .write_raw              = acpi_als_write_raw,
>  };
>
>  static int acpi_als_add(struct acpi_device *device)
> @@ -189,6 +234,9 @@ static int acpi_als_add(struct acpi_device *device)
>
>         device->driver_data = indio_dev;
>         als->device = device;
> +       als->scale = 1;
> +       als->uscale = 0;
> +       als->offset = 0;
>         mutex_init(&als->lock);
>
>         indio_dev->name = ACPI_ALS_DEVICE_NAME;
> --
> 2.1.0
>