Setting USB probe priority...

[Hans Petter Selasky]

On 08/06/14 01:50, Peter Losher wrote:
> (please include my and Dan's email in any responses as we normally don't lurk on the USB mailing list)
>
> So @work we use serial->USB TTY MUX's to handle our serial console needs, and at some sites we have a need that is greater than a single 16 port device (the max you can get).  The problem is that with two of these 16 port USB devices is that sometimes during a reboot that the "second" device gets probed first and so the first 16 and second 16 /dev/ttyU* blocks swap around... which of course plays havoc with any symlinks we have to the devices in rtty or conserver. :(
>
> Is there any way to tell the USB code to always select a certain device first?  I assume this has been a issue with USB storage devices so this shouldn't be a new issue.  And I tried searching for a answer on the web to no avail.
>
> Ideas?

Hi,

USB enumerates in sequential order, but sometimes devices might not be 
ready to enumerate, and then a port is skipped.

Does the device have a serial number?

usbconfig -d X.Y dump_device_desc |grep iSerial

If yes, this can be filtered by a devd rule, when the device attaches, 
and then you can switch the serial number to create any symbolic links.

--HPS