[LAU] Teufel PC Bamster not getting connected on USB?

[David Kastrup]

David Kastrup <dak-mXXj517/zsQ at public.gmane.org> writes:

> Max
> <abonnements-yNUSWsLiBm554TAoqtyWWQ-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org>
> writes:
>
>> On 12/11/2017 06:55 PM, David Kastrup wrote:
>>> Clemens Ladisch
>>> <clemens-P6GI/4k7KOmELgA04lAiVw-XMD5yJDbdMReXY1tMh2IBg-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org>
>>> writes:
>>>
>>> Aaaaaand another data point.  If I switch the Bamster on _before_
>>> booting the laptop, it will stay around and work on USB.  It just won't
>>> stand for hotplugging.  That's not the first device I had this effect
>>> with, but the other device was an Expresscard with TI chipset (with a
>>> built-in PCI-Express to PCI bridge, so no USB).
>>
>> which Kernel version is this?
>
> Linux version 4.13.0-19-lowlatency (buildd at lcy01-amd64-021) (gcc
> version 7.2.0 (Ubuntu 7.2.0-8ubuntu3)) #22-Ubuntu SMP PREEMPT Mon Dec
> 4 12:59:42 UTC 2017
>
> Some more data points: boot with device plugged in but turned off: will
> not turn on successfully afterwards.  Wait for desktop to turn on before
> turning device on: will not turn on successfully.
>
> Boot with device on: will work.  Turn off and on again, refuses to
> work.

[...]

> So this really looks like it would be connected with the "can't add hid
> device" message.  Immediately afterwards the device disconnects.
>
> But when booting with the device, it works nicely and does something
> with the hid.
>
> There is also a wireless card on USB and a card reader (express slot),
> but the other Thinkpad T61 I tried has neither.  So I don't think they
> are related.
>
> So what's up with the usbhid here?

Another data point: I can use the PC Bamster by first removing the
snd_usb_audio module, then switching on the PC Bamster (which then stays
on), then reloading the usb_snd_audio module.

So the essential thing seems to be that the snd_usb_audio module must
not be loaded when switching the PC Bamster on, or it will get turned
off again.  Loading it afterwards is fine (and of course required to
actually work with the device).

-- 
David Kastrup