[OpenWrt-Devel] uqmi - Specifying Link Protocol (libqmi --device-open-net=net-802-3 option)

[Bjørn Mork]

John Crispin <blogic at openwrt.org> writes:

> we noticed that qmi is not working properly today and are working on a fix.
>
> 	John
>
> On 01/10/2014 21:12, Spam Catcher wrote:
>> I'm trying to use uqmi with a Sierra Wireless MC7354 and MC7750.  On
>> both modules I'm able to bring up a connection to the cell network, but
>> cannot send or receive anything on the wwan0 interface. After much
>> digging I found an option for libqmi that specifies using ethernet
>> headers instead of raw IP (--device-open-net=net-802-3).  When I
>> specified this option with libqmi, both modules came up with an IP
>> address immediately and allowed traffic to pass without issue. Is there
>> an equivalent parameter I can use for uqmi?  Or maybe even a compilation
>> flag to have it always requested?
>> 
>> I'll only be using LTE mode, so the firmware bug where 3G and 4G behave
>> differently shouldn't affect me (I think).

LTE or not should not make any difference wrt configuring the modem for
802.3 headers.  The qmi_wwan driver always assumes that the modem is in
802.3 mode, and since it doesn't participate in QMI at all it depends on
the userspace application putting the modem in the appropriate mode.

The problem is that this setting is persistent and can be changed by
other drivers, firmware upgrade applications, other QMI applications.
So any QMI userspace application using the qmi_wwan driver should
*always* verify and/or set 802.3 mode before doing anything else. The
persistence makes this appear unnecessary for most modems, but trusting
that is fooling yourself.

Older QMI firmwares (with no QMI_WDA support) have no way to verify
the mode, so the only option is to blindly set 802.3 using  the
QMI_CTL_SET_DATA_FORMAT request.  Newer firmwares (which means anything
running on a MC7354) will have QMI_WDA allowing you to check the current
setting.



Bjørn
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