On 6/29/20 6:59 PM, Guenter Roeck wrote:
+linux-hwmon@xxxxxxxxxxxxxxx
On Mon, Jun 29, 2020 at 08:31:11AM +0200, zlukwins wrote:
Hi,
I am OpenBMC FW developer working currently on some power measurement stuff.
I would like to have maximum rated input power for pmubus device available
in hwmon sysfs. This value is read by MFR_PIN_MAX command:
/MFR_PIN_MAX//
//The MFR_PIN_MIN command sets or retrieves the maximum rated value, in
watts, of//
//the input power./
Interesting typo in the PMBus specification. Yes, it really does associate
MFR_PIN_MIN - which doesn't seem to exist - with the maximum rated output
power.
And I wondering which attribute shell be used to expose that value in sysfs.
I went through documentation
(https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface) and found
the following:
power[1-*]_max Maximum power.
Unit: microWatt
RW
But it looks like it is already occupied by PIN_OP_WARN_LIMIT.
Maybe new attribute shall be used? If so how to call that?
None of the standard attributes reports (or is supposed to report) rated
values, so we can not just use any of those.
Also, we can not just add a single attribute to handle this situation,
for the simple reason that there are many more similar attributes.
PMBus specifies (this is from version 1.3.1):
MFR_VIN_MIN
MFR_VIN_MAX
MFR_IIN_MAX
MFR_PIN_MAX
MFR_VOUT_MIN
MFR_VOUT_MAX
MFR_IOUT_MAX
MFR_POUT_MAX
MFR_TAMBIENT_MAX
MFR_TAMBIENT_MIN
MFR_MAX_TEMP_{1,2.3}
All those report rated values. I do see the need/desire for reporting such
information. The only real solution I can see is to add a new set of
attributes to the hwmon ABI. Something like:
currentX_rated_min # for consistency
currentX_rated_max
inX_rated_min
inX_rated_max
powerX_rated_min # for consistency
powerX_rated_max
tempX_rated_min
tempX_rated_max
plus maybe, for consistency:
humidityX_rated_min
humidityX_rated_max
Those would be read-only attributes.
Thoughts, comments, feedback anyone ?
Thanks,
Guenter
I really like your proposition but I guess we need to wait few more days
for the feedback.
But have some questions here.
What about potential next steps when we all agreed to follow that
approach. Should documentation modification reach upstream repository
first and then e.g. pmbus hwmon module implementation?
Thanks
Zbigniew
