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[PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation

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  [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation Stefan Brüns <stefan.bruens@rwth-aachen.de> - 2017-07-17 01:40 +0200
    Re: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor  attribute documentation Jonathan Cameron <jic23@kernel.org> - 2017-07-17 23:00 +0200
      Re: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor  attribute documentation Brüns, Stefan <Stefan.Bruens@rwth-aachen.de> - 2017-07-17 23:50 +0200

#1688565 — [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation

The ina2xx driver appeared in the Linux kernel version 4.5, but provided
no documentation. Contrary to other uses of resistance in IIO, ina2xx uses
microohms instead of ohms in the sysfs attribute.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
---
 Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
new file mode 100644
index 000000000000..9525098f6822
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
@@ -0,0 +1,7 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_shunt_resistor
+Date:		December 2015
+KernelVersion:	4.5
+Contact:	linux-iio@vger.kernel.org
+Description: 	The value of the shunt resistor connected to the V_IN+ and V_IN-
+		inputs, used to compute the current flowing through the shunt and
+		the corresponding power. In microohms.
-- 
2.13.2

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#1689469 — Re: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation

On Mon, 17 Jul 2017 01:34:10 +0200
Stefan Brüns <stefan.bruens@rwth-aachen.de> wrote:

> The ina2xx driver appeared in the Linux kernel version 4.5, but provided
> no documentation. Contrary to other uses of resistance in IIO, ina2xx uses
> microohms instead of ohms in the sysfs attribute.
> 
> Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
This has me confused.  The documentation is already
there and lists it as being in ohms.

Ah, subtle filename difference.  Docs in are
Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc

This attribute effectively exists for other parts
as well now.

Jonathan
> ---
>  Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc | 7 +++++++
>  1 file changed, 7 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> new file mode 100644
> index 000000000000..9525098f6822
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> @@ -0,0 +1,7 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/in_shunt_resistor
> +Date:		December 2015
> +KernelVersion:	4.5
> +Contact:	linux-iio@vger.kernel.org
> +Description: 	The value of the shunt resistor connected to the V_IN+ and V_IN-
> +		inputs, used to compute the current flowing through the shunt and
> +		the corresponding power. In microohms.

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#1689512 — Re: [PATCH 2/2] iio: Documentation: Add ina2xx shunt_resistor attribute documentation

On Montag, 17. Juli 2017 22:53:57 CEST Jonathan Cameron wrote:
> On Mon, 17 Jul 2017 01:34:10 +0200
> 
> Stefan Brüns <stefan.bruens@rwth-aachen.de> wrote:
> > The ina2xx driver appeared in the Linux kernel version 4.5, but provided
> > no documentation. Contrary to other uses of resistance in IIO, ina2xx uses
> > microohms instead of ohms in the sysfs attribute.
> > 
> > Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
> 
> This has me confused.  The documentation is already
> there and lists it as being in ohms.

Which obviously, from reading the source code, is wrong - it uses microohms.

Also, the current Description contains IMHO irrelevant stuff:
"The value of the shunt resistor may be known only at runtime fom an
 eeprom content read by a client application."

> Ah, subtle filename difference.  Docs in are
> Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc

Well spotted ...

> This attribute effectively exists for other parts
> as well now.

My grep foo failed me here, the only parts I could find are the MAX9611 (which 
specifies and uses ohms) and the INA2xx.

adc/qcom-spmi-iadc.c allows to read the RSENSE value from device tree 
(specified in microohms), but does not expose it via sysfs.

Can you point me to other devices?

Slightly off-topic: Some attributes in iio are read from device-tree (e.g. 
shunt resistor values), should the iio documentation point to the dt bindings? 
Currently, only mount_matrix in sysfs-bus-iio vaguely mentions device-tree.

Kind regards,

Stefan

> > ---
> > 
> >  Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> > b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc new file mode
> > 100644
> > index 000000000000..9525098f6822
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina2xx-adc
> > @@ -0,0 +1,7 @@
> > +What:		/sys/bus/iio/devices/iio:deviceX/in_shunt_resistor
> > +Date:		December 2015
> > +KernelVersion:	4.5
> > +Contact:	linux-iio@vger.kernel.org
> > +Description: 	The value of the shunt resistor connected to the V_IN+ 
and
> > V_IN- +		inputs, used to compute the current flowing through the shunt
> > and +		the corresponding power. In microohms.

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