Re: [PATCH 1/3] iio: add IIO_MASSCONCENTRATION channel type

[Tomasz Duszynski <tduszyns@gmail.com>]

On Sun, Nov 25, 2018 at 08:35:07AM +0000, Jonathan Cameron wrote:
> On Sat, 24 Nov 2018 23:14:13 +0100
> 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.
> I initially wondered why these particular numbers and why don't
> we provide an attribute specify this separately?
>
> However google suggests these two are pretty much the only
> ones anyone worries about in pollution sensors.  I ended
> up fairly quickly at the EPA website
> https://www.epa.gov/pm-pollution/table-historical-particulate-matter-pm-national-ambient-air-quality-standards-naaqs
> which tells me these two have be used since about 1987.
>

Usually sensors can measure more than just PM10 and PM2.5. Fairy
common is measurement of PM1.0. SPS30 additionally measures PM4.0
but frankly I don't now know exactly what's the real usecase for that.

> So I think the modifier route is the right approach here
> (I think we've gotten this wrong in the past such as light
> sensor colours where the list keeps on growing).
>
> I would like a reference or two in the docs though to point
> people to these definitions.
>

Okay, will add something reasonable so everyone interested
could get the basic idea quickly.

> Thanks,
>
> Jonathan
>
> >
> > 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,
> >  };
> >
> >  enum iio_modifier {
> > @@ -87,6 +88,8 @@ enum iio_modifier {
> >  	IIO_MOD_VOC,
> >  	IIO_MOD_LIGHT_UV,
> >  	IIO_MOD_LIGHT_DUV,
> > +	IIO_MOD_PM2p5,
> > +	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;
>