On Thu, 22 Sep 2005, Patrick Hilt wrote:

> Hi!
> Just a quick question:
> Is there any (good) way to trigger re-enumeration of the USB bus from
> software?

It's not clear that this is a good idea.  It would mean losing all the 
settings for devices you had already enumerated.

>  The situation is that I am working on a custom design where
> two boards are housed in the same case and connected via USB. One
> board runs Linux and implements the host controller. The other board
> runs a different OS. When power is supplied, the two boards boot
> independently and the Linux one is faster (;-). Because of some
> shortcomings, the second board cannot reset the USB bus it's on and is
> therefore never detected.

That shouldn't matter.  USB peripherals don't have to reset anything, they 
only have to connect to the bus.  The host is supposed to take care of 
everything else.  Maybe your problem is really that the peripheral 
connects to the bus before it's ready to be enumerated.

>  So I am looking for a way to periodically
> re-enumerate the USB bus under software control from the Linux side.

One way to do it, although a pretty drastic way, is to rmmod the host 
controller driver module and then modprobe it.

Alan Stern



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