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Date: Sun, 07 Sep 2014 09:10:48 +0200
From: Hans Petter Selasky <hps@selasky.org>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
Subject: Re: What to do if USB stack seems dead
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Cc: freebsd-hackers@freebsd.org, Maxim V FIlimonov <che@bein.link>
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On 09/07/14 08:42, Poul-Henning Kamp wrote:
> --------
> In message <540B7AC4.9060504@selasky.org>, Hans Petter Selasky writes:
>> On 09/06/14 21:57, Maxim V FIlimonov wrote:
>>> Lately, I've been heavily experimenting with different USB devices (for
>>> instance, USB to TTL one, but that's another story), and at a moment I
>>> encountered that the system doesn't react on new USB devices connected. The
>>> connected devices work fine, though. The question is: what can I do in such a
>>> case if I don't want to reboot my box?
>>>
>>
>> Hi,
>>
>> If a TTY port is not closed, it will prevent other USB devices on that
>> particular USB controller from enumerating.
>
> I'm pretty sure I have seen this "dead USB" thing on
>
> 	FreeBSD ni.freebsd.dk 11.0-CURRENT FreeBSD 11.0-CURRENT #3 r270830:
>
> without any USB/TTY ports being involved at all...
>

Hi,

If it is a USB SW problem, you should see that the USB explore / RootHub 
threads are stuck. Else it is a USB HW problem.

--HPS