Sierra Wireless EM7455

Dan Williams dcbw at
Thu Jun 9 15:09:47 UTC 2016

On Thu, 2016-06-09 at 09:27 +0200, Ralph Plawetzki wrote:
> Am 08.06.2016 um 15:25 schrieb Bjørn Mork:
> > 
> > Well, back to the real problem and possible soution: You can flip
> > the
> > modem into QMI mode by using a Sierra vendor specific QMI request,
> > via
> > the QMI-over-MBIM service.  I don't think this is implemented in
> > any
> > "proper" tools, but I have a perl script which can do it here:
> >
> > 
> > BIG FAT WARNING:  I would not have tried this if I were you.  The
> > script
> > is never tested on any modem with an OEM vendor PID originally,
> > AFAIK.
> Thanks for pointing me to this possibility. I will not try it.
> In my experience with linux systems over the years "try and error"
> does
> not lead to anything. The only way out of an issue is to identify the
> problem.
> Right this seems not possible here. I am neither a driver developer
> nor
> a hardware specialist. I understand that the modem has 'Qualcomm
> Snapdragon' in its name, so probably is running in QMI mode. I don't
> know what QMI mode really means and where the difference is compared
> to
> MBIM mode.

QMI and MBIM are just different ways to talk to the modem's firmware.
 Like languages.  QMI is proprietary to Qualcomm, older than MBIM, and
ties much more closely to the firmware architecture of Qualcomm chips.

MBIM is a "standard" protocol that is used by many vendors, and is
built-in to Windows 8 and later, so if a modem supports MBIM then it
doesn't need special drivers in Windows.  It's supported by many
vendors, regardless of what chips are in their modems.

To make it easier to integrate into Windows, Qualcomm provided firmware
to modem vendors that use their chips that speaks the MBIM protocol.
 Some vendors choose to use it by default.  Some vendors also allow
special commands to switch Qualcomm firmware between speaking QMI and
MBIM by default.  This is what the Sierra tool that Bjorn is talking
about does.

> I also understand that MBIM is more usual and used on a broader base
> and
> that newer devices need this magic code FCC authentication to get
> activated.

Only newer Sierra devices based on Qualcomm chips need this command.
 Other vendors like Huawei, Novatel, ZTE, etc don't appear to need this
QMI command, even if they use Qualcomm chips inside.  Not sure why
Sierra is doing this, but they appear to be the only ones so far.

> My modem needs that too and I can get it online, but as described it
> gets a local IP then. From searching the web, many people had
> problems
> getting the modem online or getting an IP at all.
> So badly for me, there is something wrong with my hardware. As I do
> not
> know which of the involved components (NetworkManager, ModemManager
> or
> maybe the firmware) is responsible for retrieving an IP, from my
> point
> of view it does not make sense to go any further from this point.
> > 
> > This is a Lenovo modem in a Lenovo laptop, right?  If not then I
> > got the
> > rest wrong.  But in case that is correct:
> Well, the laptop is bought from Lenovo, the modem inside identifies
> itself as 'Sierra Wireless EM7455 Qualcomm Snapdragon X7 LTE-A'. I
> don't
> know if that means that it is a Lenovo modem.

If the modem's usb vendor ID is a Lenovo vendor ID, then it's a Lenovo
customized Sierra-produced modem.  Vendors like Lenovo and HP do this
to ensure that only approved modems are used in their own machines,
technically to ensure that the modem and antenna solution are paired
together.  This is theoretically for regulatory approval, since the
modem *and* antenna are certified together, not just the modem itself.
 Antenna can have a big effect on how the modem performs and whether it
meets regulator requirements.  The cynical among us will say this is
actually to ensure that users have to pay HP money for a modem instead
of getting them on the secondary market though.


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