[ltp] Re: Verifying Linux compatibiliy for the LTE modems in the 2nd gen X1 Carbon

Bjørn Mork linux-thinkpad@linux-thinkpad.org
Wed, 05 Mar 2014 10:58:27 +0100

[ Sorry about using the "wrong" from-address on my first mail, causing
  the list to reject it. I did intend it to go to the list as well.
  And thanks for fixing that by quoting it all :-)

Peter FP1 Zhang <zhangfp1@lenovo.com> writes:

> Hello Bjørn,
> Nice to hear from you. 
> Before discussing the details, let me explain current OEM Linux ecosystem.
> Every year we will certify our Thinkpads with Ubuntu and Redhat, but
> it is a pity that both of the two distributions do not include 3G &
> LTE function testing in their certification check list.

Yes, this is very unfortunate. I don't think most consumers will
understand that "Certified for Ubuntu/Redhat" still allows some parts of
the machine to not work at all in Linux.

But that's not a problem I expect you to be able to fix.  It's not
really so much a problem with Ubuntu and Redhat either.  It's more about
the certification industry in general.

> And the most important factor is, no any big customers require our
> sales to support 3G & LTE for Linux. That is why there is no official
> support on that function by default.

Perfectly understandable. I'm not going to claim that there are many
Linux users who care about 3G & LTE, so I'm not surprised that no big
customers require it. Just judging by looking at my co-workers, who
mostly use Thinkpads with 3G modules and have free mobile broadband, I
do not see many real users. But there are some, including some Linux

But that doesn't count for much. Any effort you'd put into this would
have to come out of some other budget. Maybe the "public reputation"?  I
guess your appearance here already earned Lenovo a large bonus on that
account :-)

> I ever talked this topic with Serria and Ericsson. Ericsson is willing
> to support if any customers raised the requirements.

Again as I'd expect.  Ericsson (and/or ST-Ericsson when they existed)
have contributed the NCM class driver to Linux, and they used to work
tightly with the ModemManager developers. I'm sure Ericsson is both
capable and willing to do the work if any customers required them to.

> But I was told Serria has no any Linux driver support for their
> chipsets. Since they think it is not worth to invest on that.

Sierra do support Linux based embedded systems, and have also
contributed drivers to mainline. So there is unfortunately not much
doubt that their decision not to support PC modules on Linux is based on
real world experience. They are most likely correct that it isn't worth
it.  At least not if you are going to do a lot of development and/or end
user support.

But the current state is that Microsoft has given the Linux community,
Ericsson, Sierra and other modem vendors a lot of help through their
Windows 8 requirements.  We do now have a mobile broadband USB device
class, CDC MBIM, and a driver for this class is included in recent
(v3.8+) Linux kernels.  All new 3G & LTE modems made for laptop use is
likely to support this device class, because Microsoft requires them to.

So adding Linux support for 3G & LTE modems has suddenly become much
easier than it used to be.  It is mainly about testing out the modem
with the driver already in the Linux mainline kernel, and maybe fix up
some minor compatibility issues.

>  Without
> any real cases with big shipping volume, our company have no any
> position to push Serria/Intel to enable it. That is the root cause.
> If you have a big deal which need LTE on Linux, pls don't hesitate to
> let us know. I will try to ask our sales to push them again. Thanks.

I do believe you and your sales. Linux support for this feature is
probably not worth any development cost, and most likely not any end
user support either.  The niche is just too small

What I am hoping for is sort of a "best effort testing".  Please try out
the mainline drivers and a recent ModemManager with your newest 3G & LTE
modules and see if there are any issues which could easily be fixed.  I
do not expect you to put any resources into fixing the issues, and
certainly not to offer any Linux support for 3G & LTE. But if you could
report test results back to the community, then that would be a great
help for all us voluntary developers who try to support these things on
our spare time.

Personally, as one of the cdc_mbim developers, I am thrilled to recieve
*any* reports from *anyone* having tested a yet-unknown-to-me 3G/LTE
module, whether the test was successful or not.  That's how we improve
the support. None of us are in a position to buy every modem module out
there, and even less so when we talk about laptop vendor modules.  We
depend on user reports.

Assuming you have early access to lots of new hardware, you could make a
big difference by simply trying it out and sending some logs back.

I realize that this isn't a known support model for any laptop vendor
today, but I thought I could try to convince you since you have alrady
proven to be much more open to new ideas than anyone else by
participating in this forum :-) Thanks for doing that regardless of how
you decide to deal with my request.