Huawei me906s-158

[Bjørn Mork]

Andreas Fett <andreas.fett at secunet.com> writes:
> On 07/03/16 09:38, Bjørn Mork wrote:
>> Since the modem definitely works in MBIM modem, it's more likely that
>> there is something interfering with the MBIM control channel in Linux.
>> For example some unknown process reading from the character device, or
>> something sending unknown commands to it which makes it lock up.  We
>> have seen examples of both those problems in the past.
>> 
>> Use "lsof /dev/cdc-wdm0" to make sure there are no unwanted listeners.
>> 
>> Make sure nothing probes the device for any other protocol than MBIM
>> (some Sierra Wireless Qualcomm based devices are for example known to
>> switch control protocol to whatever probes it first, regardless of USB
>> descriptors saying MBIM).
>
> At the moment I'm trying to capture the usb traffic starting with the
> initialization of the cdc_mbim module, while not loading any modules not
> needed.
>
> I'm somewhat confused however about the relation between the cdc_mbim
> and the cdc_ncm driver. It is loaded when inserting the cdc_mbim module
> via modprobe.

MBIM is a variant of NCM (MBIM was known as "NCM 2.0" in the initial
draft versions). The Linux cdc_mbim driver implementation takes
advantage of this by reusing most of the logic from cdc_ncm. So cdc_mbim
depends on cdc_ncm, causing the module tools to autoload cdc_ncm
whenever you load cdc_mbim.

> Should I load the huawei_cdc_mbim module (for which you
> posted the patch with the proper ID earlier), too?

No, that is not necessary in MBIM mode.  The huawei_cdc_mbim driver is
used by one of the other USB configurations.  It's a slightly different
variant of NCM again, also reusing most of cdc_ncm.

Confusing?  Sure :)



Bjørn