Re: While waiting for MBIM support

[Dan Williams <dcbw redhat com>]

On Thu, 2013-04-04 at 19:48 +0200, Bjørn Mork wrote:
> I was hoping to help finishing the MM MBIM support, but have to realize
> that available spare time is insufficient...  And with no one sponsoring
> Aleksander's work I guess MBIM just will have to wait.
>
> This means that we should ensure that MBIM devices continue to work
> using whatever legacy mode they have.  There are several issues here:
>
> 1) devices like the Sierra Wireless MC7710 using multiple
>   configurations, where the first interface of the legacy configuration
>   is vendor specific.  The Linux kernel (USB core) will select the MBIM
>   configuration by default because non-vendor-specific configurations
>   are preferred.
>
>   Could be worked around using udev rules
>
> 2) devices like the Huawei E367, using multiple configurations to
>   support legacy modeswitching and MBIM.  The Linux kernel will select
>   the modeswitching configuration because it is first and has a proper
>   class (mass-storage).  But usb_modeswitch will switch to the MBIM
>   configuration instead of traditional modeswitching if the cdc_mbim
>   driver is available
>
>   Could be worked around using usb_modeswitch config
>
> 3) devices like the Ericsson H5321gw, having NCM compatible MBIM
>  interfaces using different altsettings.
>
>  Could be forced to NCM by setting the cdc_ncm parameter "prefer_mbim"
>  (new in Linux v3.8.5/v3.9) to false.

I forget, is this a module parameter?  If so, that's a non-starter
because userspace programs shouldn't really be loading/unloading modules
or playing around with module parameters...

Dan

> I believe MM should implement the suggested workarounds until it
> supports MBIM.  This will ensure that MM works with these MBIM devices,
> using legacy modes. And it enables us to switch to MBIM when MM is ready
> for that.
>
>
>
> Bjørn
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