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Date:   Sun, 25 Nov 2018 16:35:34 +0100
From:   Tomasz Duszynski <tduszyns@gmail.com>
To:     Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
Cc:     Matt Ranostay <matt.ranostay@konsulko.com>,
        Tomasz Duszynski <tduszyns@gmail.com>,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH 1/3] iio: add IIO_MASSCONCENTRATION channel type
Message-ID: <20181125153533.GB5053@arch>
References: <20181124221415.10081-1-tduszyns@gmail.com>
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 <20181125140316.59d9872b@archlinux>
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On Sun, Nov 25, 2018 at 02:03:16PM +0000, Jonathan Cameron wrote:
> On Sun, 25 Nov 2018 05:51:32 -0800
> Matt Ranostay <matt.ranostay@konsulko.com> wrote:
>
> > On Sat, Nov 24, 2018 at 2:14 PM Tomasz Duszynski <tduszyns@gmail.com> wrote:
> > >
> > > Measuring particulate matter in ug / m3 (micro-grams per cubic meter)
> > > is de facto standard. Existing air quality sensors usually follow
> > > this convention and are capable of returning measurements using
> > > this unit.
> > >
> > > IIO currently does not offer suitable channel type for this
> > > type of measurements hence this patch adds this.
> > >
> > > In addition, two modifiers are introduced used for distinguishing
> > > between coarse (PM10) and fine particles (PM2p5) measurements, i.e
> > > IIO_MOD_PM10 and IIO_MOD_PM2p5.
> > >
> > > Signed-off-by: Tomasz Duszynski <tduszyns@gmail.com>
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-iio | 11 ++++++++++-
> > >  drivers/iio/industrialio-core.c         |  3 +++
> > >  include/uapi/linux/iio/types.h          |  3 +++
> > >  tools/iio/iio_event_monitor.c           |  6 ++++++
> > >  4 files changed, 22 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> > > index 8127a08e366d..ce0ed140660d 100644
> > > --- a/Documentation/ABI/testing/sysfs-bus-iio
> > > +++ b/Documentation/ABI/testing/sysfs-bus-iio
> > > @@ -1684,4 +1684,13 @@ KernelVersion:   4.18
> > >  Contact:       linux-iio@vger.kernel.org
> > >  Description:
> > >                 Raw (unscaled) phase difference reading from channel Y
> > > -               that can be processed to radians.
> > > \ No newline at end of file
> > > +               that can be processed to radians.
> > > +
> > > +What:          /sys/bus/iio/devices/iio:deviceX/in_massconcentration_pm2p5_input
> > > +What:          /sys/bus/iio/devices/iio:deviceX/in_massconcentrationY_pm2p5_input
> > > +What:          /sys/bus/iio/devices/iio:deviceX/in_massconcentration_pm10_input
> > > +What:          /sys/bus/iio/devices/iio:deviceX/in_massconcentrationY_pm10_input
> > > +KernelVersion: 4.21
> > > +Contact:       linux-iio@vger.kernel.org
> > > +Description:
> > > +               Mass concentration reading of particulate matter in ug / m3.
> > > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > > index a062cfddc5af..2a9ef600c1fb 100644
> > > --- a/drivers/iio/industrialio-core.c
> > > +++ b/drivers/iio/industrialio-core.c
> > > @@ -87,6 +87,7 @@ static const char * const iio_chan_type_name_spec[] = {
> > >         [IIO_GRAVITY]  = "gravity",
> > >         [IIO_POSITIONRELATIVE]  = "positionrelative",
> > >         [IIO_PHASE] = "phase",
> > > +       [IIO_MASSCONCENTRATION] = "massconcentration",
> > >  };
> > >
> > >  static const char * const iio_modifier_names[] = {
> > > @@ -127,6 +128,8 @@ static const char * const iio_modifier_names[] = {
> > >         [IIO_MOD_Q] = "q",
> > >         [IIO_MOD_CO2] = "co2",
> > >         [IIO_MOD_VOC] = "voc",
> > > +       [IIO_MOD_PM2p5] = "pm2p5",
> > > +       [IIO_MOD_PM10] = "pm10",
> > >  };
> > >
> > >  /* relies on pairs of these shared then separate */
> > > diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
> > > index 92baabc103ac..465044b42af5 100644
> > > --- a/include/uapi/linux/iio/types.h
> > > +++ b/include/uapi/linux/iio/types.h
> > > @@ -46,6 +46,7 @@ enum iio_chan_type {
> > >         IIO_GRAVITY,
> > >         IIO_POSITIONRELATIVE,
> > >         IIO_PHASE,
> > > +       IIO_MASSCONCENTRATION,
> >
> > So I'm guessing IIO_CONCENTRATION can't be scaled to the micro-grams
> > per cubic meter?
>
> Currently concentration is defined as a percentage reading of a substance
> (which does make me wonder if it is meant to be percentage of the volume or
> percentage of the mass?)  Either way, if can't convert to a density measurement
> as it's a unit free ratio (I think).
>

And this is the main reason behind introducing a new channel type.

> >
> > >  };
> > >
> > >  enum iio_modifier {
> > > @@ -87,6 +88,8 @@ enum iio_modifier {
> > >         IIO_MOD_VOC,
> > >         IIO_MOD_LIGHT_UV,
> > >         IIO_MOD_LIGHT_DUV,
> > > +       IIO_MOD_PM2p5,
> >
> > I know this is unit of measure but the lowercase p in IIO_MOD_PM2p5 is
> > a bit non-standard for iio defines/enum.
> It is a bit odd and will get us scripted reports so maybe best to
> just go upper case and not worry about it.
>

Initially I came up with IIO_MOD_PM2_5 but eventually replaced
underscore with 'p' meaning 'decimal point'. Anyway, I am okay with the
suggested change.

> Jonathan
> >
> > - Matt
> >
> > > +       IIO_MOD_PM10,
> > >  };
> > >
> > >  enum iio_event_type {
> > > diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
> > > index ac2de6b7e89f..f0fcfeddba2b 100644
> > > --- a/tools/iio/iio_event_monitor.c
> > > +++ b/tools/iio/iio_event_monitor.c
> > > @@ -60,6 +60,7 @@ static const char * const iio_chan_type_name_spec[] = {
> > >         [IIO_GRAVITY] = "gravity",
> > >         [IIO_POSITIONRELATIVE] = "positionrelative",
> > >         [IIO_PHASE] = "phase",
> > > +       [IIO_MASSCONCENTRATION] = "massconcentration",
> > >  };
> > >
> > >  static const char * const iio_ev_type_text[] = {
> > > @@ -115,6 +116,8 @@ static const char * const iio_modifier_names[] = {
> > >         [IIO_MOD_Q] = "q",
> > >         [IIO_MOD_CO2] = "co2",
> > >         [IIO_MOD_VOC] = "voc",
> > > +       [IIO_MOD_PM2p5] = "pm2p5",
> > > +       [IIO_MOD_PM10] = "pm10",
> > >  };
> > >
> > >  static bool event_is_known(struct iio_event_data *event)
> > > @@ -156,6 +159,7 @@ static bool event_is_known(struct iio_event_data *event)
> > >         case IIO_GRAVITY:
> > >         case IIO_POSITIONRELATIVE:
> > >         case IIO_PHASE:
> > > +       case IIO_MASSCONCENTRATION:
> > >                 break;
> > >         default:
> > >                 return false;
> > > @@ -200,6 +204,8 @@ static bool event_is_known(struct iio_event_data *event)
> > >         case IIO_MOD_Q:
> > >         case IIO_MOD_CO2:
> > >         case IIO_MOD_VOC:
> > > +       case IIO_MOD_PM2p5:
> > > +       case IIO_MOD_PM10:
> > >                 break;
> > >         default:
> > >                 return false;
> > > --
> > > 2.19.2
> > >
>