Subject: power and USB devices
To: None <>
From: Steven M. Bellovin <>
List: netbsd-users
Date: 08/06/2005 16:59:32
I'm curious when USB devices receive power from the ports on the 

Two recent observations prompted this query.  First, I've noticed that 
when I "stop" a flash disk on Windows, the LED turns off.  That's a 
very useful visual cue.  By contrast, on NetBSD it's always 
illuminated, whether the drive is mounted or not.  In other words, it 
doesn't depend on whether or not the device is open.  It also seems 
likely that Windows hasn't simply powered down the port, since it 
immediately notices if I reinsert the drive.

I also tried to charge my Palmpilot (Tungsten E) via my USB port on 
NetBSD.  After a fair number of hours, there was only a small 
difference in the battery charge level.  I decided to use jpilot to 
back up the device -- that seemed to cause it to charge the battery a 
lot, as if having the device open mattered.  Note that the ucom0/uvisor0
device did not appear until after I started the hotsync operation on 
the Palmpilot, i.e., the Palmpilot itself did not open its end of the 
connection.  Should charging it that way have worked?

		--Steven M. Bellovin,