Sensor value calculation formula

[Deng Tyler]

Hi all:
    Thank for your kindly reply and that really help me. I meat same
problem discussed before by Patrick and Qianlihu as below. I add

EXTRA_OECONF_append = " --enable-remove-from-dbus-on-fail" in hwmon
append, but it still not working. Hwmon monitor service still
terminated  after init() called exit(0). I also try add
"EXTRA_OECONF_append = " --enable-negative-errno-on-fail"" and still
not working.

What do I miss configuration or understand?

>* On my board,when host powed off, the fan would stop.
*>>* then,phosphor-hwmon failed to start
*>>* debug:
*>>* cat /sys/class/hwmon/hwmon0/fan1_input
*>*         read error Connection timedout.
*>>* edit the config file,
*>*         LABEL_fan1 = fan1
*>*         REMOVERCS = 110 // 110 means ETIMEDOUT
*>>* when host powerd on
*>*         1. echo add > /sys/class/hwmon/hwmon0/uevent
*>*         2. phosphor-hwmon started
*>*         3. host power off
*>*         4. phosphor-hwmon did not exit.
*>*         5. cpu usage of hwmon-read would be 4%
*>>* when host powerd off
*>*         1. echo add > /sys/class/hwmon/hwmon0/uevent
*>*         2. failed to start phosphor-hwmon.
*>>* I found when phosphor-hwmon init
*>>*    Sensor::addValue would read fan1_input(there is no fan1_fault in sysfs),
*>*    and it caused read timedout unexpection.
*>>*    so init failed.
*>>* On my board,I  want to boot the bmc with phosphor-hwmon when host
powered off.
*>>* what should I do ?
*
You have a couple options, one will basically remove the sensor from
dbus on read failure, the other just leaves it but sets the value to
-errno (in this case ETIMEDOUT).

There are two configuration option switches for these, you can add it
to your bbappend:

EXTRA_OECONF_append = " --enable-remove-from-dbus-on-fail"


EXTRA_OECONF_append = " --enable-negative-errno-on-fail"

Milton Miller II <miltonm at us.ibm.com> 於 2019年3月9日 週六 上午12:34寫道：

> On  03/06/2019 around 11:36PM in some timezone,  Deng Tyler wrote:
>
> >Hi Emily
> >    I found it hardcoded in phosphor-hwmon for different sensor type.
> >I think that scale value may be customized for more flexible to fit
> >custom platform.
>
> Assuming that the sensor is exposed though a kernel sysfs hwmon
> file, you should be looking to specify a gain for the file in sysfs
> instead.
> Many sense devices already support a scale in the device tree.
>
> >
> >Tyler
> >Emily Shaffer <emilyshaffer at google.com> 於 2019年3月7日 週四 下午1:22寫道：
> >Tyler,
> >
> >Sorry that I forgot. Yes, the scale is hardcoded for certain sensor
> >types, ie voltage is always millivolts. I have asked about this
> >before but maybe someone else on the list can give a better answer
> >why that's the case.
> >
>
> The Linux kernel hwmon API specifies the units for different sensors
> as they are exposed in sysfs.  Hence the hwmon to dbus bridge can
> hard code the unit for a given type of sensor.
>
> The hwmon API is documented at
> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface
> or
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/hwmon/sysfs-interface
>
> The above spec is linked as "HWMon interface" under the headings
> "D-BUS" then "Path Definitions" headings in
> https://github.com/openbmc/docs/blob/master/sensor-architecture.md
>
> milton
>
> Speaking for myself only.
>
>
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