From: Greg KH <greg@kroah.com>
To: linux-hotplug@vger.kernel.org
Subject: Re: USB Hub Port Power Control and Hotplug Events
Date: Fri, 11 Aug 2006 08:37:41 +0000 [thread overview]
Message-ID: <20060811083741.GA9989@kroah.com> (raw)
In-Reply-To: <9b1737410608101621g61587b05s113501b16d38b7b6@mail.gmail.com>
On Fri, Aug 11, 2006 at 09:39:47AM +0200, Guennadi Liakhovetski wrote:
> On Thu, 10 Aug 2006, Andy Dalton wrote:
>
> > While experimenting, I noticed something a bit strange. If I power
> > down a port on the USB hub, then later power it back on, I do *not*
> > get a hotplug removal event on power off, but I *do* get an insertion
> > event on power on.
>
> It has been discussed on the USB-devel list. The thing is - the hub
> doesn't report a "port status change" on "port power off". It's on power
> on it first reports a "disconnect" and then immediately a "new device".
> And the system cannot really simulate this event for you because the "port
> power off" command can come from various places - kernel drivers, user
> space. So, your only option seems to be to use the fact that it's you who
> issues the command, so, you know that the device is gone. Just use this
> knowledge.
>
> Not sure, but I don't think you can tell the kernel that the device is
> gone...
No, the USB stack does not allow you to do this at this point in time,
sorry.
You can unbind a device from a driver though, that would prevent it from
being used by any userspace programs.
thanks,
greg k-h
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prev parent reply other threads:[~2006-08-11 8:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-10 23:21 USB Hub Port Power Control and Hotplug Events Andy Dalton
2006-08-11 7:39 ` Guennadi Liakhovetski
2006-08-11 8:37 ` Greg KH [this message]
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