| Message ID | 20210516044315.116290-1-liambeguin@gmail.com |
|---|---|
| Headers | show |
| Series | hwmon: (iio_hwmon) optionally force iio channel type | expand |
On 5/15/21 9:43 PM, Liam Beguin wrote: > Add a devicetree binding to optionally force a different IIO channel > type. > > This is useful in cases where ADC channels are connected to a circuit > that represent another unit such as a temperature or a current. > > `channel-types` was chosen instead of `io-channel-types` as this is not > part of the iio consumer bindings. > > In the current form, this patch does what it's intended to do: > change the unit displayed by `sensors`, but feels like the wrong way to > address the problem. > > Would it be possible to force the type of different IIO channels for > this kind of use case with a devicetree binding from the IIO subsystem? > That doesn't make sense to me. If an ADC is used to report temperatures, it would be a thermistor, and the ntc_thermistor driver should be used. Not sure what to do with currents, but overriding "voltage" with "current" seems wrong. Guenter > It would be convenient to do it within the IIO subsystem to have the > right unit there too. > > Thanks for your time, > Liam > > Liam Beguin (2): > hwmon: (iio_hwmon) optionally force iio channel type > dt-bindings: hwmon: add iio-hwmon bindings > > .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > drivers/hwmon/iio_hwmon.c | 2 + > 2 files changed, 43 insertions(+) > create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > > > base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 >
On Sun, 16 May 2021 00:43:13 -0400 Liam Beguin <liambeguin@gmail.com> wrote: > Add a devicetree binding to optionally force a different IIO channel > type. > > This is useful in cases where ADC channels are connected to a circuit > that represent another unit such as a temperature or a current. > > `channel-types` was chosen instead of `io-channel-types` as this is not > part of the iio consumer bindings. > > In the current form, this patch does what it's intended to do: > change the unit displayed by `sensors`, but feels like the wrong way to > address the problem. > > Would it be possible to force the type of different IIO channels for > this kind of use case with a devicetree binding from the IIO subsystem? > > It would be convenient to do it within the IIO subsystem to have the > right unit there too. > > Thanks for your time, > Liam Hi Liam, +CC Peter for AFE part. It's an interesting approach, but I would suggest we think about this a different way. Whenever a channel is being used to measure something 'different' from what it actually measures (e.g. a voltage ADC measuring a current) that reflects their being some analog component involved. If you look at drivers/iio/afe/iio-rescale.c you can see the approach we currently use to handle this. Effectively what you add to devicetree is a consumer of the ADC channel which in turn provides services to other devices. For this current case it would be either a current-sense-amplifier or a current-sense-shunt depending on what the analog front end looks like. We have to describe the characteristics of that front end which isn't something that can be done via a simple channel type. That afe consumer device can then provide services to another consumer (e.g. iio-hwmon) which work for your usecase. The main limitation of this approach currently is you end up with one device per channel. That could be improved upon if you have a usecase where it matters. I don't think we currently have an equivalent for temperature sensing but it would be easy enough to do something similar. Jonathan > > Liam Beguin (2): > hwmon: (iio_hwmon) optionally force iio channel type > dt-bindings: hwmon: add iio-hwmon bindings > > .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > drivers/hwmon/iio_hwmon.c | 2 + > 2 files changed, 43 insertions(+) > create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > > > base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717
Hi Guenter, On Sun May 16, 2021 at 4:56 AM EDT, Guenter Roeck wrote: > On 5/15/21 9:43 PM, Liam Beguin wrote: > > Add a devicetree binding to optionally force a different IIO channel > > type. > > > > This is useful in cases where ADC channels are connected to a circuit > > that represent another unit such as a temperature or a current. > > > > `channel-types` was chosen instead of `io-channel-types` as this is not > > part of the iio consumer bindings. > > > > In the current form, this patch does what it's intended to do: > > change the unit displayed by `sensors`, but feels like the wrong way to > > address the problem. > > > > Would it be possible to force the type of different IIO channels for > > this kind of use case with a devicetree binding from the IIO subsystem? > > > > That doesn't make sense to me. If an ADC is used to report temperatures, > it would be a thermistor, and the ntc_thermistor driver should be used. > Not sure what to do with currents, but overriding "voltage" with > "current" > seems wrong. Thanks for pointing out the ntc_thermistor. It makes sense that the ADC channel would become a thermistor. I'll have a look and see if it fits my use case. Liam > > Guenter > > > It would be convenient to do it within the IIO subsystem to have the > > right unit there too. > > > > Thanks for your time, > > Liam > > > > Liam Beguin (2): > > hwmon: (iio_hwmon) optionally force iio channel type > > dt-bindings: hwmon: add iio-hwmon bindings > > > > .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > > drivers/hwmon/iio_hwmon.c | 2 + > > 2 files changed, 43 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > > > > > > base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 > >
Hi Jonathan, On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: > On Sun, 16 May 2021 00:43:13 -0400 > Liam Beguin <liambeguin@gmail.com> wrote: > > > Add a devicetree binding to optionally force a different IIO channel > > type. > > > > This is useful in cases where ADC channels are connected to a circuit > > that represent another unit such as a temperature or a current. > > > > `channel-types` was chosen instead of `io-channel-types` as this is not > > part of the iio consumer bindings. > > > > In the current form, this patch does what it's intended to do: > > change the unit displayed by `sensors`, but feels like the wrong way to > > address the problem. > > > > Would it be possible to force the type of different IIO channels for > > this kind of use case with a devicetree binding from the IIO subsystem? > > > > It would be convenient to do it within the IIO subsystem to have the > > right unit there too. > > > > Thanks for your time, > > Liam > > Hi Liam, > > +CC Peter for AFE part. > > It's an interesting approach, but I would suggest we think about this > a different way. > > Whenever a channel is being used to measure something 'different' from > what it actually measures (e.g. a voltage ADC measuring a current) that > reflects their being some analog component involved. > If you look at drivers/iio/afe/iio-rescale.c you can see the approach > we currently use to handle this. Many thanks for pointing out the AFE code. That look like what I was hoping to accomplish, but in a much better way. > > Effectively what you add to devicetree is a consumer of the ADC channel > which in turn provides services to other devices. For this current case > it would be either a current-sense-amplifier or a current-sense-shunt > depending on what the analog front end looks like. We have to describe > the characteristics of that front end which isn't something that can > be done via a simple channel type. > Understood. My original intention was to use sensors.conf to do the conversions and take into accounts those parameters. > That afe consumer device can then provide services to another consumer > (e.g. iio-hwmon) which work for your usecase. > > The main limitation of this approach currently is you end up with > one device per channel. That could be improved upon if you have a > usecase > where it matters. > > I don't think we currently have an equivalent for temperature sensing > but it would be easy enough to do something similar. Wonderful, thanks again for pointing out the AFE! Liam > > Jonathan > > > > > > Liam Beguin (2): > > hwmon: (iio_hwmon) optionally force iio channel type > > dt-bindings: hwmon: add iio-hwmon bindings > > > > .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > > drivers/hwmon/iio_hwmon.c | 2 + > > 2 files changed, 43 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > > > > > > base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717
On 5/16/21 8:02 AM, Liam Beguin wrote: > Hi Jonathan, > > On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: >> On Sun, 16 May 2021 00:43:13 -0400 >> Liam Beguin <liambeguin@gmail.com> wrote: >> >>> Add a devicetree binding to optionally force a different IIO channel >>> type. >>> >>> This is useful in cases where ADC channels are connected to a circuit >>> that represent another unit such as a temperature or a current. >>> >>> `channel-types` was chosen instead of `io-channel-types` as this is not >>> part of the iio consumer bindings. >>> >>> In the current form, this patch does what it's intended to do: >>> change the unit displayed by `sensors`, but feels like the wrong way to >>> address the problem. >>> >>> Would it be possible to force the type of different IIO channels for >>> this kind of use case with a devicetree binding from the IIO subsystem? >>> >>> It would be convenient to do it within the IIO subsystem to have the >>> right unit there too. >>> >>> Thanks for your time, >>> Liam >> >> Hi Liam, >> >> +CC Peter for AFE part. >> >> It's an interesting approach, but I would suggest we think about this >> a different way. >> >> Whenever a channel is being used to measure something 'different' from >> what it actually measures (e.g. a voltage ADC measuring a current) that >> reflects their being some analog component involved. >> If you look at drivers/iio/afe/iio-rescale.c you can see the approach >> we currently use to handle this. > > Many thanks for pointing out the AFE code. That look like what I was > hoping to accomplish, but in a much better way. > >> >> Effectively what you add to devicetree is a consumer of the ADC channel >> which in turn provides services to other devices. For this current case >> it would be either a current-sense-amplifier or a current-sense-shunt >> depending on what the analog front end looks like. We have to describe >> the characteristics of that front end which isn't something that can >> be done via a simple channel type. >> > > Understood. My original intention was to use sensors.conf to do the > conversions and take into accounts those parameters. > >> That afe consumer device can then provide services to another consumer >> (e.g. iio-hwmon) which work for your usecase. >> >> The main limitation of this approach currently is you end up with >> one device per channel. That could be improved upon if you have a >> usecase >> where it matters. >> >> I don't think we currently have an equivalent for temperature sensing >> but it would be easy enough to do something similar. > > Wonderful, thanks again for pointing out the AFE! > Please don't reinvent the ntc_thermistor driver. Thanks, Guenter > Liam > >> >> Jonathan >> >> >>> >>> Liam Beguin (2): >>> hwmon: (iio_hwmon) optionally force iio channel type >>> dt-bindings: hwmon: add iio-hwmon bindings >>> >>> .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ >>> drivers/hwmon/iio_hwmon.c | 2 + >>> 2 files changed, 43 insertions(+) >>> create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml >>> >>> >>> base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 >
On Sun, 16 May 2021 08:54:06 -0700 Guenter Roeck <linux@roeck-us.net> wrote: > On 5/16/21 8:02 AM, Liam Beguin wrote: > > Hi Jonathan, > > > > On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: > >> On Sun, 16 May 2021 00:43:13 -0400 > >> Liam Beguin <liambeguin@gmail.com> wrote: > >> > >>> Add a devicetree binding to optionally force a different IIO channel > >>> type. > >>> > >>> This is useful in cases where ADC channels are connected to a circuit > >>> that represent another unit such as a temperature or a current. > >>> > >>> `channel-types` was chosen instead of `io-channel-types` as this is not > >>> part of the iio consumer bindings. > >>> > >>> In the current form, this patch does what it's intended to do: > >>> change the unit displayed by `sensors`, but feels like the wrong way to > >>> address the problem. > >>> > >>> Would it be possible to force the type of different IIO channels for > >>> this kind of use case with a devicetree binding from the IIO subsystem? > >>> > >>> It would be convenient to do it within the IIO subsystem to have the > >>> right unit there too. > >>> > >>> Thanks for your time, > >>> Liam > >> > >> Hi Liam, > >> > >> +CC Peter for AFE part. > >> > >> It's an interesting approach, but I would suggest we think about this > >> a different way. > >> > >> Whenever a channel is being used to measure something 'different' from > >> what it actually measures (e.g. a voltage ADC measuring a current) that > >> reflects their being some analog component involved. > >> If you look at drivers/iio/afe/iio-rescale.c you can see the approach > >> we currently use to handle this. > > > > Many thanks for pointing out the AFE code. That look like what I was > > hoping to accomplish, but in a much better way. > > > >> > >> Effectively what you add to devicetree is a consumer of the ADC channel > >> which in turn provides services to other devices. For this current case > >> it would be either a current-sense-amplifier or a current-sense-shunt > >> depending on what the analog front end looks like. We have to describe > >> the characteristics of that front end which isn't something that can > >> be done via a simple channel type. > >> > > > > Understood. My original intention was to use sensors.conf to do the > > conversions and take into accounts those parameters. > > > >> That afe consumer device can then provide services to another consumer > >> (e.g. iio-hwmon) which work for your usecase. > >> > >> The main limitation of this approach currently is you end up with > >> one device per channel. That could be improved upon if you have a > >> usecase > >> where it matters. > >> > >> I don't think we currently have an equivalent for temperature sensing > >> but it would be easy enough to do something similar. > > > > Wonderful, thanks again for pointing out the AFE! > > > > Please don't reinvent the ntc_thermistor driver. Agreed, I'd forgotten it existed :( Had a feeling we'd solved that problem before but couldn't remember the name of the driver. The afe driver already deals with current / voltage scaling and conversion for common analog circuits. Potential dividers, current shunts etc, but they are all the linear cases IIRC. ntc_thermistor deals with the much more complex job of dealing with a thermistor. Thanks, Jonathan > > Thanks, > Guenter > > > Liam > > > >> > >> Jonathan > >> > >> > >>> > >>> Liam Beguin (2): > >>> hwmon: (iio_hwmon) optionally force iio channel type > >>> dt-bindings: hwmon: add iio-hwmon bindings > >>> > >>> .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > >>> drivers/hwmon/iio_hwmon.c | 2 + > >>> 2 files changed, 43 insertions(+) > >>> create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > >>> > >>> > >>> base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 > > >
On Sun May 16, 2021 at 12:26 PM EDT, Jonathan Cameron wrote: > On Sun, 16 May 2021 08:54:06 -0700 > Guenter Roeck <linux@roeck-us.net> wrote: > > > On 5/16/21 8:02 AM, Liam Beguin wrote: > > > Hi Jonathan, > > > > > > On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: > > >> On Sun, 16 May 2021 00:43:13 -0400 > > >> Liam Beguin <liambeguin@gmail.com> wrote: > > >> > > >>> Add a devicetree binding to optionally force a different IIO channel > > >>> type. > > >>> > > >>> This is useful in cases where ADC channels are connected to a circuit > > >>> that represent another unit such as a temperature or a current. > > >>> > > >>> `channel-types` was chosen instead of `io-channel-types` as this is not > > >>> part of the iio consumer bindings. > > >>> > > >>> In the current form, this patch does what it's intended to do: > > >>> change the unit displayed by `sensors`, but feels like the wrong way to > > >>> address the problem. > > >>> > > >>> Would it be possible to force the type of different IIO channels for > > >>> this kind of use case with a devicetree binding from the IIO subsystem? > > >>> > > >>> It would be convenient to do it within the IIO subsystem to have the > > >>> right unit there too. > > >>> > > >>> Thanks for your time, > > >>> Liam > > >> > > >> Hi Liam, > > >> > > >> +CC Peter for AFE part. > > >> > > >> It's an interesting approach, but I would suggest we think about this > > >> a different way. > > >> > > >> Whenever a channel is being used to measure something 'different' from > > >> what it actually measures (e.g. a voltage ADC measuring a current) that > > >> reflects their being some analog component involved. > > >> If you look at drivers/iio/afe/iio-rescale.c you can see the approach > > >> we currently use to handle this. > > > > > > Many thanks for pointing out the AFE code. That look like what I was > > > hoping to accomplish, but in a much better way. > > > > > >> > > >> Effectively what you add to devicetree is a consumer of the ADC channel > > >> which in turn provides services to other devices. For this current case > > >> it would be either a current-sense-amplifier or a current-sense-shunt > > >> depending on what the analog front end looks like. We have to describe > > >> the characteristics of that front end which isn't something that can > > >> be done via a simple channel type. > > >> > > > > > > Understood. My original intention was to use sensors.conf to do the > > > conversions and take into accounts those parameters. > > > > > >> That afe consumer device can then provide services to another consumer > > >> (e.g. iio-hwmon) which work for your usecase. > > >> > > >> The main limitation of this approach currently is you end up with > > >> one device per channel. That could be improved upon if you have a > > >> usecase > > >> where it matters. > > >> > > >> I don't think we currently have an equivalent for temperature sensing > > >> but it would be easy enough to do something similar. > > > > > > Wonderful, thanks again for pointing out the AFE! > > > > > > > Please don't reinvent the ntc_thermistor driver. > Agreed, I'd forgotten it existed :( Had a feeling we'd solved that > problem before > but couldn't remember the name of the driver. > > The afe driver already deals with current / voltage scaling and > conversion > for common analog circuits. Potential dividers, current shunts etc, but > they > are all the linear cases IIRC. > > ntc_thermistor deals with the much more complex job of dealing with a > thermistor. I agree, no need to reinvent this. Like Jonathan said, the ntc_thermistor driver seems to handle much more complex cases. Where would be the best place to add support for PT100 and PT1000? iio-rescale? Thanks, Liam > > Thanks, > > Jonathan > > > > > Thanks, > > Guenter > > > > > Liam > > > > > >> > > >> Jonathan > > >> > > >> > > >>> > > >>> Liam Beguin (2): > > >>> hwmon: (iio_hwmon) optionally force iio channel type > > >>> dt-bindings: hwmon: add iio-hwmon bindings > > >>> > > >>> .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ > > >>> drivers/hwmon/iio_hwmon.c | 2 + > > >>> 2 files changed, 43 insertions(+) > > >>> create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml > > >>> > > >>> > > >>> base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 > > > > >
On 5/16/21 11:14 AM, Liam Beguin wrote: > On Sun May 16, 2021 at 12:26 PM EDT, Jonathan Cameron wrote: >> On Sun, 16 May 2021 08:54:06 -0700 >> Guenter Roeck <linux@roeck-us.net> wrote: >> >>> On 5/16/21 8:02 AM, Liam Beguin wrote: >>>> Hi Jonathan, >>>> >>>> On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: >>>>> On Sun, 16 May 2021 00:43:13 -0400 >>>>> Liam Beguin <liambeguin@gmail.com> wrote: >>>>> >>>>>> Add a devicetree binding to optionally force a different IIO channel >>>>>> type. >>>>>> >>>>>> This is useful in cases where ADC channels are connected to a circuit >>>>>> that represent another unit such as a temperature or a current. >>>>>> >>>>>> `channel-types` was chosen instead of `io-channel-types` as this is not >>>>>> part of the iio consumer bindings. >>>>>> >>>>>> In the current form, this patch does what it's intended to do: >>>>>> change the unit displayed by `sensors`, but feels like the wrong way to >>>>>> address the problem. >>>>>> >>>>>> Would it be possible to force the type of different IIO channels for >>>>>> this kind of use case with a devicetree binding from the IIO subsystem? >>>>>> >>>>>> It would be convenient to do it within the IIO subsystem to have the >>>>>> right unit there too. >>>>>> >>>>>> Thanks for your time, >>>>>> Liam >>>>> >>>>> Hi Liam, >>>>> >>>>> +CC Peter for AFE part. >>>>> >>>>> It's an interesting approach, but I would suggest we think about this >>>>> a different way. >>>>> >>>>> Whenever a channel is being used to measure something 'different' from >>>>> what it actually measures (e.g. a voltage ADC measuring a current) that >>>>> reflects their being some analog component involved. >>>>> If you look at drivers/iio/afe/iio-rescale.c you can see the approach >>>>> we currently use to handle this. >>>> >>>> Many thanks for pointing out the AFE code. That look like what I was >>>> hoping to accomplish, but in a much better way. >>>> >>>>> >>>>> Effectively what you add to devicetree is a consumer of the ADC channel >>>>> which in turn provides services to other devices. For this current case >>>>> it would be either a current-sense-amplifier or a current-sense-shunt >>>>> depending on what the analog front end looks like. We have to describe >>>>> the characteristics of that front end which isn't something that can >>>>> be done via a simple channel type. >>>>> >>>> >>>> Understood. My original intention was to use sensors.conf to do the >>>> conversions and take into accounts those parameters. >>>> >>>>> That afe consumer device can then provide services to another consumer >>>>> (e.g. iio-hwmon) which work for your usecase. >>>>> >>>>> The main limitation of this approach currently is you end up with >>>>> one device per channel. That could be improved upon if you have a >>>>> usecase >>>>> where it matters. >>>>> >>>>> I don't think we currently have an equivalent for temperature sensing >>>>> but it would be easy enough to do something similar. >>>> >>>> Wonderful, thanks again for pointing out the AFE! >>>> >>> >>> Please don't reinvent the ntc_thermistor driver. > >> Agreed, I'd forgotten it existed :( Had a feeling we'd solved that >> problem before >> but couldn't remember the name of the driver. >> >> The afe driver already deals with current / voltage scaling and >> conversion >> for common analog circuits. Potential dividers, current shunts etc, but >> they >> are all the linear cases IIRC. >> >> ntc_thermistor deals with the much more complex job of dealing with a >> thermistor. > > I agree, no need to reinvent this. > > Like Jonathan said, the ntc_thermistor driver seems to handle much more > complex cases. Where would be the best place to add support for PT100 > and PT1000? iio-rescale? > Those sensors don't seem to be even useful for hardware monitoring, so if they are linear (and it looks like that that the case) iio would be a better place. Guenter