Query Sensor

[Ed Tanous]

On Tue, Jan 11, 2022 at 9:17 AM Mike Jones <proclivis at gmail.com> wrote:
>
> This is how to do it:
>
> dbus-send --system --print-reply \
>
> --dest=xyz.openbmc_project.Hwmon-5a446562b1a2e55ef11da905907088a187a66b71eb7a1f29187594c05bb8fd9a.Hwmon1 \
>
> /xyz/openbmc_project/sensors/temperature/lm75temp \
>
> org.freedesktop.DBus.Properties.Get string:xyz.openbmc_project.Sensor.Value string:Value \
>
> double:
>
>
> It is not clear to me why the second parameter string:Value
>
>
> I guessed on that and it works. Perhaps xyz…Sensor.Value is the Property name, and properties have values, so the second parameter says get the Value of a property whose name ends in .Value.\

For better or worse, the term "Value" is overloaded in both the
interface name, yz.openbmc_project.Sensor.Value, and the property name
within the interface, Value.  That's why you see it twice in this
case.  They are distinct things within the request that just happen to
share a name.  Docs for the interface and property are here:
https://github.com/openbmc/phosphor-dbus-interfaces/blob/e0674c894ed36a2e8cf96207907a531d2f514054/yaml/xyz/openbmc_project/Sensor/Value.interface.yaml#L24

Happy to see you figured it out.

>
>
> To test that, I tried string:MaxValue, and that works.
>
>
> I confirmed with this:
>
>
> busctl introspect xyz.openbmc_project.Hwmon-5a446562b1a2e55ef11da905907088a187a66b71eb7a1f29187594c05bb8fd9a.Hwmon1 /xyz/openbmc_project/sensors/temperature/lm75temp
>
>
> A very useful command.
>
>
> Also useful:
>
>
> dbus-send --system --print-reply \
>
> --dest=xyz.openbmc_project.ObjectMapper /\
>
> xyz/openbmc_project/object_mapper \
>
> xyz.openbmc_project.ObjectMapper.GetSubTree \
>
> string:"/" int32:0 array:string:"xyz.openbmc_project.Sensor.Value"
>
>
>
> Mike
>
>
> Sent from my iPad
>
> On Jan 10, 2022, at 4:50 PM, Ed Tanous <edtanous at google.com> wrote:
>
> On Mon, Jan 10, 2022 at 3:47 PM Mike Jones <proclivis at gmail.com> wrote:
>
>
> Hi,
>
>
> I could not find an example of a sensor query in the docs. I assume something like this:
>
>
> dbus-send --system --print-reply \
>
>
> --dest=xyz.openbmc_project.Hwmon-5a446562b1a2e55ef11da905907088a187a66b71eb7a1f29187594c05bb8fd9a.Hwmon1 \
>
>
> /xyz/openbmc_project/sensors/temperature/lm75temp
>
>
> xyz.openbmc_project.Sensor.Property.Get xyz.openbmc_project.Sensor.Value \
>
>
> double:
>
>
>
> I don't have an example offhand, but the interface you're looking for
> in the bolded area is
> org.freedesktop.DBus.Properties.Get
>
> Stack overflow for essentially the same question with an example:
> https://stackoverflow.com/questions/48648952/set-get-property-using-dbus-send
>
>
> With the bold interface replaced with something correct.
>
>
> Can some one give me an example, and a url about how to query properties?
>
>
> Mike
>
>
> Sent from my iPad