[Nut-upsuser] Cyber power CP1500AVR required pollonly?

[Selva Nair]

Ubuntu 22.04
NUT 2.7.4
CYberPower CP1500AVRLCDa  using usbhid-ups

Hello,

The above combination works well for a few minutes -- including shutdown on
pulling power or on upsmon -c fsd, notifications etc. Until the driver
starts reporting error in libusb_get_string, kernel messages on
USDEVFS_CONTROL failures and upsmon logs 'Data stale'

It seems the UPS does not support interrupt transfer (or is buggy). On
adding pollonly=enabled to ups.conf, everything appears to be working
fine again.

Is this a known issue? I have seen a number of success reports on this
model, none mentioning the need for pollonly, so wondering whether I
should troubleshoot this further.

Thanks,

Selva