Huawei me906s-158

[Bjørn Mork]

Andreas Fett <andreas.fett at secunet.com> writes:

> Hi Bjørn,
>
> On 04/04/16 16:38, Bjørn Mork wrote:
>> This makes sense even if the USB captures don't show any other
>> differences.  The firmware might assume that the configuration always
>> switches from 0 to either 1, 2 or 3 and then stays there.  That's what
>> would happen on a Windows system.  There are most likely a number of
>> internal firmware settings associated with such configuration switches.
>> Failure to reset them could very well mess up things beyond rescue.
>
> Attached there is a usb capture of the following:
>
> System (cold) boots with /sys/bus/usb/devices/1-2/bConfigurationValue of
> "2".
>
> echo 0 > /sys/bus/usb/devices/1-2/bConfigurationValue
> echo 3 > /sys/bus/usb/devices/1-2/bConfigurationValue

Hmm, rereading this while trying to make a case out of it, I realize
that I missed the fact that you need to switch to configuration 0
(i.e. unconfigured).  For some reason I thought you had to switch to
configuration 1.  But that doesn't work either, does it?

Then I guess we have a problem, because AFAICS the kernel will have to
make some decision by default.  We could in theory make the
configuration switching always go via the unconfigured state, but adding
some arbitrary delay between the states is out of the question.  That's
better left for userspace then.

> cdc_mbim is loaded via udev and attaches.
>
> echo Y > /sys/class/net/wwan0/cdc_mcn/ndp_to_end

A device quirk for this one is simpler though.  Just one question to be
sure: It does not work without this?



Bjørn