[Nut-upsdev] [PATCH/RFC 1/1] APC smart driver update and new features.

[Arjen de Korte]

Citeren Michal Soltys <soltys op ziu.info>:

> Then, the other options, that is if:
>
> - additional LB checks are to remain in main.c
> - new apcsmart's "ignorelb" option to have the desired effect
> - the checks are to use well known battery.{runtime,charge}.low, and  
> be universal at the same time
>
> the likely options are:
>
> - handle this at driver level - e.g. preserve the immutable flag if  
> already set without setting rw (if necessary, e.g. in apcsmart if  
> ignorelb is set), ignore polling, adjust the code so it works fine,  
> etc.
> - go back to minbatt/mintime
> - add e.g. ST_FLAG_USER_OVERRIDE which would be used for any (and  
> only for) override.* in ups.conf (instead of  
> ST_FLAG_USER_IMMUTABLE), while not being encumbered by "must not be  
> rw" constraint
>
> The 1st option looks good ?

Yes. You really must handle this situation at driver level. We don't  
want to get into a situation where a variable is R/W (through upsrw),  
but any changes send to the UPS will not be visible because there is  
an override set in ups.conf. Whether or not it is possible to grant an  
override in ups.conf also depends on the UPS and therefor must be  
handled by the driver. For instance, if you want to override  
battery.charge.low, you must be able to ignore the low battery charge  
warning from the UPS. Many models (not necessarily APC) will shut down  
automatically after a low battery condition is detected, so this may  
not be possible.

In the vast majority of cases, if a UPS reports either  
battery.charge.low or battery.runtime.low, these will be usable for  
determining when it is time to shutdown the load. If this doesn't work  
reliably, chances are that the underlying mechanism of calculating  
charge or runtime left is broken. There is nothing we can possibly do  
with that. Also consider the possibility that problems you might be  
seeing are due to glitches in the status bits. If that is the case, it  
might help to only set the LB flag if it is reported three times in a  
row (note that this flag will be latched immediately if the UPS is on  
battery).

Best regards, Arjen
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