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Date: Thu, 9 May 2024 21:31:25 +0200
From: Dimitri Fedrau <dima.fedrau@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Lars-Peter Clausen <lars@...afoo.de>,
Andrew Hepp <andrew.hepp@...pp.dev>,
Marcelo Schmitt <marcelo.schmitt1@...il.com>,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] iio: temperature: mcp9600: set channel2 member
Am Sun, May 05, 2024 at 11:15:41AM +0100 schrieb Jonathan Cameron:
> On Tue, 30 Apr 2024 14:21:57 +0200
> Dimitri Fedrau <dima.fedrau@...il.com> wrote:
>
> > Am Tue, Apr 30, 2024 at 01:11:02PM +0100 schrieb Jonathan Cameron:
> > > On Tue, 30 Apr 2024 14:05:31 +0200
> > > Dimitri Fedrau <dima.fedrau@...il.com> wrote:
> > >
> > > > Set channel2 member of channel 0 to IIO_MOD_TEMP_OBJECT and set modified
> > > > member to 1.
> > > This an ABI change, so needs a strong argument + must be a fix
> > > rather than an improvement. So why does this need to change?
> > >
> > Hi Jonathan,
> >
> > I don't know if it is an valid argument but when using tool "iio_info"
> > the temp_object wasn't displayed at all. After adding these two lines
> > the temp_object is displayed. Don't know if it is a problem with the
> > userspace tools.
>
> Just to check, it displayed not temperature channel for this?
>
It did it correctly when reading from /sys/bus/iio/devices/iio\:device0
but when using "iio_info" it didn't. See below.
> If you could send the file listing of the appropriate
> /sys/bus/iio/devices/iio\:deviceX/ directory that would be great.
>
root@...pberrypi3-64:~# ls -al /sys/bus/iio/devices/iio\:device0/
drwxr-xr-x 3 root root 0 May 4 20:11 .
drwxr-xr-x 4 root root 0 May 4 20:11 ..
-rw-r--r-- 1 root root 4096 May 4 20:11 in_temp_ambient_raw
-rw-r--r-- 1 root root 4096 May 4 20:11 in_temp_ambient_scale
-rw-r--r-- 1 root root 4096 May 4 20:11 in_temp_raw
-rw-r--r-- 1 root root 4096 May 4 20:11 in_temp_scale
-r--r--r-- 1 root root 4096 May 4 20:11 name
lrwxrwxrwx 1 root root 0 May 4 20:11 of_node -> ../../../../../../../firmware/devicetree/base/soc/i2c@...04000/temperature-sensor@67
drwxr-xr-x 2 root root 0 May 4 20:11 power
lrwxrwxrwx 1 root root 0 May 4 20:11 subsystem -> ../../../../../../../bus/iio
-rw-r--r-- 1 root root 4096 May 4 20:11 uevent
-r--r--r-- 1 root root 4096 May 4 20:11 waiting_for_supplier
> It is possible the tools don't cope with a mixture of modified and unmodified
> channels (without index). Whilst the ABI docs don't say you can't do this
> it is a rather obscure corner case.
>
I think you are right, below are my findings. When doing a cat from
in_temp_ambient_raw or in_temp_raw the results are correct, when using
iio_info there is only a single channel displayed with four attributes.
root@...pberrypi3-64:~# cat /sys/bus/iio/devices/iio\:device0/in_temp_ambient_raw; cat /sys/bus/iio/devices/iio\:device0/in_temp_raw; iio_info
314
540
iio_info version: 0.25 (git tag:b6028fde)
Libiio version: 0.25 (git tag: b6028fd) backends: local xml ip usb serial
IIO context created with local backend.
Backend version: 0.25 (git tag: b6028fd)
Backend description string: Linux raspberrypi3-64 6.9.0-rc1-g7584c270afae-dirty #239 SMP PREEMPT Thu May 9 20:11:36 CEST 2024 aarch64
IIO context has 2 attributes:
local,kernel: 6.9.0-rc1-g7584c270afae-dirty
uri: local:
IIO context has 3 devices:
hwmon0: cpu_thermal
1 channels found:
temp1: (input)
1 channel-specific attributes found:
attr 0: input value: 42932
No trigger on this device
hwmon1: rpi_volt
1 channels found:
in0: (input)
1 channel-specific attributes found:
attr 0: lcrit_alarm value: 0
No trigger on this device
iio:device0: mcp9600
1 channels found:
temp_ambient: (input)
4 channel-specific attributes found:
attr 0: raw value: 314
attr 1: raw value: 314
attr 2: scale value: 62.500000
attr 3: scale value: 62.500000
1 device-specific attributes found:
attr 0: waiting_for_supplier value: 0
No trigger on this device
With the patch setting modified and channel2:
root@...pberrypi3-64:~# ls -al /sys/bus/iio/devices/iio\:device0/
drwxr-xr-x 3 root root 0 May 9 18:21 .
drwxr-xr-x 4 root root 0 May 9 18:21 ..
-rw-r--r-- 1 root root 4096 May 9 18:22 in_temp_ambient_raw
-rw-r--r-- 1 root root 4096 May 9 18:22 in_temp_ambient_scale
-rw-r--r-- 1 root root 4096 May 9 18:22 in_temp_object_raw
-rw-r--r-- 1 root root 4096 May 9 18:22 in_temp_object_scale
-r--r--r-- 1 root root 4096 May 9 18:21 name
lrwxrwxrwx 1 root root 0 May 9 18:22 of_node -> ../../../../../../../firmware/devicetree/base/soc/i2c@...04000/temperature-sensor@67
drwxr-xr-x 2 root root 0 May 9 18:22 power
lrwxrwxrwx 1 root root 0 May 9 18:22 subsystem -> ../../../../../../../bus/iio
-rw-r--r-- 1 root root 4096 May 9 18:22 uevent
-r--r--r-- 1 root root 4096 May 9 18:22 waiting_for_supplier
root@...pberrypi3-64:~# cat /sys/bus/iio/devices/iio\:device0/in_temp_ambient_raw; cat /sys/bus/iio/devices/iio\:device0/in_temp_object_raw; iio_info
318
523
iio_info version: 0.25 (git tag:b6028fde)
Libiio version: 0.25 (git tag: b6028fd) backends: local xml ip usb serial
IIO context created with local backend.
Backend version: 0.25 (git tag: b6028fd)
Backend description string: Linux raspberrypi3-64 6.9.0-rc1-g51f9ab5c4102-dirty #240 SMP PREEMPT Thu May 9 20:21:32 CEST 2024 aarch64
IIO context has 2 attributes:
local,kernel: 6.9.0-rc1-g51f9ab5c4102-dirty
uri: local:
IIO context has 3 devices:
hwmon0: cpu_thermal
1 channels found:
temp1: (input)
1 channel-specific attributes found:
attr 0: input value: 45084
No trigger on this device
hwmon1: rpi_volt
1 channels found:
in0: (input)
1 channel-specific attributes found:
attr 0: lcrit_alarm value: 0
No trigger on this device
iio:device0: mcp9600
2 channels found:
temp_ambient: (input)
2 channel-specific attributes found:
attr 0: raw value: 317
attr 1: scale value: 62.500000
temp_object: (input)
2 channel-specific attributes found:
attr 0: raw value: 532
attr 1: scale value: 62.500000
1 device-specific attributes found:
attr 0: waiting_for_supplier value: 0
No trigger on this device
> The maping from hotjunction to object isn't totally clear to me.
> Mind you neither is the mapping from cold junction to ambient (that one is
> a bit stronger as the datasheet tables assume
> Cold Junction Temperature == Ambient Temperature.
>
> Example of why I don't like this is object is no obvious if the hotjunction
> is in a gas or liquid. The object defintion was I think added for infrared
> temperature sensors where you get nothing meaningful without an object to
> emit the infrared.
>
Thanks for the explanation, somehow I was satisfied with the mapping
from hotjunction to object. :) If the object is gas or liquid ?!
> An alternative would be to provide an index for both channels. Also an ABI
> change, but avoids the object / hot junction issue and I would assume works
> fine with iio_info.
>
I will have a look into it and come up with a patch eventually. Don't
know if its worth changing the ABI. What do you think ?
Dimitri
..
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