linux-kernel - Re: [RFC]Is usb port number fixed?

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Date:	Tue, 24 Apr 2012 10:14:05 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Wang YanQing <udknight@...il.com>
cc:	Anil Nair <anilcoll90@...il.com>, Greg KH <greg@...ah.com>,
	lkml <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [RFC]Is usb port number fixed?

On Tue, 24 Apr 2012, Wang YanQing wrote:

> On Mon, Apr 23, 2012 at 11:13:06AM -0400, Alan Stern wrote:
> > The port numbers are determined by the hardware -- each set of wires
> > has its own port number.  The numbers have nothing to do with
> > bandwidth.
> Could you figure out the codes in kernel that read out the port number from
> hub, if there is a piece of codes do that things?

In drivers/usb/core/hub.c, look through the hub_events() routine.  
There are several function calls similar to this one:

			ret = hub_port_status(hub, i,
					&portstatus, &portchange);

Here i is the port number.  This asks the hub to send back status and 
change information for port i.  (See also the code for the 
hub_port_status() and get_port_status() routines.)

Alan Stern

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