[Nut-upsdev] HA: PowerCOM HID PDC non-compliance

[Morozov Alexey]

Dear Arjen,
Thank you for your comments. I've forwarded it to software engineers to take into account in future development.
 
Sincerely yours
--
Alexey Morozov
distribution manager 

________________________________

От: Arjen de Korte [mailto:nut+devel at de-korte.org]
Отправлено: Ср, 20.01.2010 11:50
Кому: Morozov Alexey
Копия: nut-upsdev
Тема: PowerCOM HID PDC non-compliance



Alexey,

I posted this before, but never got a reply. So I'm reposting this again.

In the present HID PDC implementation by PowerCOM, expect problems 
with the non-compliant implementation of the DelayBeforeShutdown and 
DelayBeforeStartup pages.

Third party applications will expect that these follow the HID PDC 
specifications if you name them like this (and break terribly in the 
process). In NUT we can (for now) easily implement the PowerCOM 
specific formatting rules, but not all applications may be able to do 
so. The same goes for UPS.PowerSummary.Voltage, 
UPS.PowerSummary.ConfigVoltage, UPS.Battery.Voltage and 
UPS.Battery.ConfigVoltage. These should deal with the battery voltage, 
not the output voltage like implemented in the PowerCOM HID now.

If in the future (?) PowerCOM has newer UPS designs that unlike the 
present one are native HID PDC from the start (instead of a serial 
protocol encapsulated in HID PDC), this will be a problem. It would 
require different ways to deal with these, based on the model of the 
UPS (compliant or non-compliant versions). Generally it is *very* poor 
design practice to *not* follow a specification. Please consider to 
*not* use the standard Power Device Pages (x84) in cases like these, 
but to create vendor specific ones instead (pages 0xFF00 to 0xFFFF are 
reserved for that). It is almost always better to *not* have a HID PDC 
path than to have an *incorrect* implemented one.

So instead of using 0x00840056 (DelayBeforeStartup) and 0x00840057 
(DelayBeforeShutdown), use 0xFFFF0056 (PCMDelayBeforeStartup) and 
0xFFFF0057 (PCMDelayBeforeShutdown) instead. This would allow 
applications that know about the PowerCOM specific implementation to 
use these values and not break ones that don't.

Best regards, Arjen
--
Please keep list traffic on the list



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