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Opinions about using USB serial numbers

On Saturday 20 March 2004 17:43, M. Warner Losh wrote:
> In message: <20040320052007_(_dot_)_GC33602_(_at_)_cicely12_(_dot_)_cicely_(_dot_)_de>
>             Bernd Walter <ticso_(_at_)_cicely12_(_dot_)_cicely_(_dot_)_de> writes:
> : I have a lot to do with systems using many USB devices of the same
> : kind.
> : Currently device are named acording to their probing order.
> : That result in the problematic that device names can change after
> : reboot or replugging in different order.
> :
> : I would like to add functionality for creating alias devnodes
> : including the serial numbers (if the device has one setup).
> : E.g. for a ucom(4) device you will get /dev/ucom0 and
> : ucom.serialnumber. If the device has no serial numer there will be
> : just /dev/ucom0 as befor.
> :
> : Another solution could be to create the nodes in a tree form:
> : /dev/usbchannel0/hubport1/pubport2/ucom
> : That would work for devices without serial numbers too, but I
> : personally dislike this way.
> I'd rather that we have a generic binding of a device instance number
> to a pnp location.
> However, having said that, you can use devd to extract the information
> from the node and then create a symbolic link...

Using the serial number would give the ability to reliably connect to a 
specific device, or to know that it is not currently present in the 
system.  For certain embedded applications, that could be very nice.

         "Where am I, and what am I doing in this handbasket?"

Wes Peters                                                  Softweyr LLC
wes_(_at_)_softweyr_(_dot_)_com                                    http://softweyr.com/