unnoticed disconnect

[Andriy Gapon]

I have a strange problem - when I disconnect a certain USB card reader
its umass* and da* devices are not removed, there is complete silence in
the system log and usbdevs -vd still shows it as connected.
Restarting usbd and/or running usbd -e doesn't change anything.
If I reconnect the device there is zero reaction as well and da* devices
are unusable (any access produces several BBB ... IOERROR).
But if attach another USB device (e.g. USB flash drive) while the reader
is disconnected then the system notices that it's actually gone and
performs all the necessary disconnect actions.

This is quite weird for me. My question if this is something most likely
caused by software or something caused by the hardware. And if the
latter - what is most likely at fault: the reader, connecting cable,
physical port, hub ?

-- 
Andriy Gapon