On 4/20/19 10:31 AM, Guenter Roeck wrote: > On 4/20/19 9:43 AM, Florian Fainelli wrote: >> Hi Sudeep, Guenter, >> >> The current SCMI hwmon support does not seem to make use of the sensor >> scale/unit as defined in the sensor replies (or the update scale for >> that matter). >> >> I came up with the patch below which gets the job done, but I am worried >> about possibly breaking people's SCMI deployments and sensors reading >> because they may have intentionally or not already decided to return a >> value which is scaled the way Linux's hwmon expect it, and may, or may >> not have populated a valid unit number in the sensor reply. >> >> Ideally we should probably do two conversions: >> >> - from within scmi_sensor_reading_get(), scale the value as indicated by >> the reply >> - from within scmi_hwmon_read(), take that scaled value and apply the >> necessary conversion expected by Linux's HWMON conventions (e.g.: >> reporting voltage as mV values) >> >> What do you think? >> > > Reported values have to follow HWMON conventions. If not, this is a bug > and needs to get fixed. The argument about not changing the userspace ABI > does not apply to bugs. Upon re-reading the SCMI specification, what is not clear to me is whether you have the liberty to: - target the Linux HWMON sensor units as specified by Documentation/hwmon/sysfs-interface by e.g.: putting a millidegree Celsius value in the SCMI reply and an power of 10 multiplier value of 0 (which would be treated as not doing any scaling) - must provide the raw value as provided by the sensor as well as indicate the scale, e.g.: millidegree celsius and specifying a scale of -3 Sudeep can you clarify how you would approach making use (or not) of the power of 10 multiplier as defined by the SCMI specification? Thanks! -- Florian
