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From: David Heinzelmann <>
To: Greg KH <>
Cc: David Heinzelmann <>,
Subject: Re: [PATCH] Check for changed device descriptors when a connection-change occurs before validating the connection.
Date: Fri, 20 Sep 2019 15:17:26 +0200
Message-ID: <20190920131726.GA5913@dhe-pc> (raw)
In-Reply-To: <>


sorry for the wrong patch format.

I am trying to detect a change. At the moment I think the change could be ignored if a
port connection-change occurs and the port status has again the 'PORT_CONNECTION' bit set. 

I have a fx3 device which does a re-enumeration after a firmware download. This is working
as expected and I am seeing a 'remove event' and a 'add event' monitoring via udevadm. But
if I connect multiple devices at the same time via an usb hub I am sometimes not receiving
a 'remove event' and 'add event' for a single device.

I think the problem could be that when a device disconnects and the port connection-change
occurs and before the 'PORT_CONNECTION' bit is checked the device could already be
reconnected and the 'PORT_CONNECTION' bit is set. Therefore I think it is not correct to
resuscitate the exisiting device.

On Fri, Sep 20, 2019 at 10:55:56AM +0200, Greg KH wrote:
> On Fri, Sep 20, 2019 at 12:36:28PM +0200, David Heinzelmann wrote:
> > When a port connection-change occurs the hub driver tries to resuscitate an existing device.
> > Activated from a firmware download a usb device can re-enumerate with new or changed device
> > descriptors. Therefore it will be checked for changed device descriptors before the connection
> > is resuscitated and the connection-change event is ignored.
> Please wrap your lines at 72 columns :(
> Anyway, what problem are you trying to solve here?  What is broken with
> how things work today?  Are you trying to ignore a change that is
> currently showing up as a change, or trying to do the opposite?
> thanks,
> greg k-h

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-20 10:36 David Heinzelmann
2019-09-20  8:55 ` Greg KH
2019-09-20 13:17   ` David Heinzelmann [this message]
2019-09-20 12:15     ` Greg KH
2019-09-20 15:33       ` David Heinzelmann
2019-09-23 14:49         ` Alan Stern
2019-09-24 10:01           ` David Heinzelmann
2019-09-25 14:20             ` Alan Stern
2019-09-30  7:26               ` David Heinzelmann
2019-09-30 14:25                 ` Alan Stern
2019-10-04 13:23                   ` David Heinzelmann
2019-10-04 14:17                     ` Alan Stern
2019-10-07  8:47                       ` David Heinzelmann
2019-10-07 14:01                         ` Alan Stern
2019-10-07 15:35                           ` Greg KH
2019-10-08  8:09                             ` [PATCH v4] usb: hub: Check device descriptor before resusciation David Heinzelmann
2019-10-08 12:55                               ` Greg KH
2019-10-08 16:10                                 ` David Heinzelmann
2019-10-08 15:17                                   ` Greg KH
2019-10-09  4:46                             ` [PATCH v5] " David Heinzelmann

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