Overlays for routers (especially OnHub)?

[Rolls Openwrt]

Hi All,

I've started looking into what it might take to get OpenWRT running on my old Tp-link Onhub routers.  One of the first steps I was hoping to take was to get a dev build of ChromiumOS running on the router (rootfs verification disabled, more debug logging, etc.).

As I went through the developer guide (https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#initialize-the-build-for-a-board), I ran into an issue when trying to configure the target board: I should have realized it earlier, but there are no overlays in the ChromiumOS repository (https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/overlays/;bpv=1) for any of the routers on the list of devices (https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/).

Are these routers closed source in a way that other ChromeOS devices aren't?  Is there any chance of these overlays becoming open source at any point?  What leads to an overlay being closed or open source?

I did find a thread from way back in 2018 with some similar questions, but no resolution.

Thanks for the help!

[Mike Frysinger]

unfortunately the overlays have yet to be released.  i've pushed for it a couple of times but have had a hard time getting cooperation from the respective teams.  i don't see it ever changing, especially with the move/integration with Nest orgs.

even if the device overlays were made public, i think it will be a hard time getting the software stack properly released too.  so you'd have limited success with a functional router built on top of Chromium OS.

fwiw, the devices are pinned now to the R94 release branch.  all support has been deleted in newer branches.

-mike

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[Rolls Openwrt]

Thanks for the quick reply Mike.  Bummer that these won't ever see the light of day.

[ggg]

On Monday, June 13, 2022 at 8:49:23 PM UTC-7 rolls....@gmail.com wrote:

Hi All,

I've started looking into what it might take to get OpenWRT running on my old Tp-link Onhub routers.  One of the first steps I was hoping to take was to get a dev build of ChromiumOS running on the router (rootfs verification disabled, more debug logging, etc.). 

That was a reasonable idea but not a feasible one. My advice is to look at "Google Wifi" support under IPQ4019 chipset in OpenWRT since that too was a Chrome OS device ("gale v2"):

   https://openwrt.org/toh/google/wifi

To get TP-Link Onhub ("whirlwind") running, one needs to replicate the "gale v2" support but for IPQ8064 instead. I have already pulled the necessary the whirlwind (and arkham) device tree bits from the chromeos-3.14 kernel branch but haven't spent the time to figure out to integrate that into the OpenWRT builds (ie add another flavor to the IPQ8064 builds which includes the device tree).

In any case, I strongly recommend copying the "VPD" partition to a safe place from the devices you test with. Device specific information (Wifi radio settings, MAC addresses, etc) in the VPD partition.

As I went through the developer guide (https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#initialize-the-build-for-a-board), I ran into an issue when trying to configure the target board: I should have realized it earlier, but there are no overlays in the ChromiumOS repository (https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/overlays/;bpv=1) for any of the routers on the list of devices (https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/).

Are these routers closed source in a way that other ChromeOS devices aren't?

Yes. The overlays contain Google's cloud-based proprietary router management. As the Google Wifi (gale) support shows, the overlays are not needed to run Openwrt. Both the coreboot and kernel sources are published.

  Is there any chance of these overlays becoming open source at any point?

No.
 

  What leads to an overlay being closed or open source?

Proprietary software is by definition closed source.

 

I did find a thread from way back in 2018 with some similar questions, but no resolution. 

Thanks for the help!

cheers,

grant

 

[Rolls Openwrt]

Thanks Grant,

Yeah, I had started working on copying the device trees into OpenWRT (see my fork here https://github.com/rmelick/openwrt/pull/1/files), but this is the first time I've ever gotten this deep into linux, so I basically have no idea what I'm doing.

I've been posting some of my progress at the end of the thread on the OpenWRT forum (https://forum.openwrt.org/t/onhub-tp-link-tgr1900-future-support/17899/42?page=2).

For copying the VPD partition off the device I'm playing with: how would I actually go about doing that?  I've been to activate "developer mode" on the OnHub , but haven't been able to get any kind of terminal or shell access to it.  Do you know if there's a way to get serial access to these devices?  I've found what I think is the SWD debug port (still waiting on my usb -> swd stick to arrive in the mail to try it out), but am also just realizing that SWD isn't really designed to give you a console.

Thanks for the help!

Russell

[Grant Grundler]

On Wed, Jun 15, 2022 at 8:59 PM Rolls Openwrt <rolls....@gmail.com> wrote:

Thanks Grant,

Yeah, I had started working on copying the device trees into OpenWRT (see my fork here https://github.com/rmelick/openwrt/pull/1/files), but this is the first time I've ever gotten this deep into linux, so I basically have no idea what I'm doing.

You are doing well. Don't stop now. :)

 

I've been posting some of my progress at the end of the thread on the OpenWRT forum (https://forum.openwrt.org/t/onhub-tp-link-tgr1900-future-support/17899/42?page=2).

Yup - I've followed this thread in the past and happy to see the updates on it. I'm assuming you've read the Oct 2021 updates on this thread.

 

For copying the VPD partition off the device I'm playing with: how would I actually go about doing that?

I had forgotten VPD is actually in the SPI flash shared with Coreboot/Depthcharge bootloaders. As long as you aren't running flashrom VPD should be safe.

But to answer your question, the VPD can be read using flashrom - though I don't recall the exact command offhand.

 

  I've been to activate "developer mode" on the OnHub , but haven't been able to get any kind of terminal or shell access to it.  Do you know if there's a way to get serial access to these devices?

I thought folks (outside of Google) had already sorted this out but it might only be for the Asus Onhub (arkham). Earlier in the same thread that you referenced above (17899)

You might want to review the videos from this Youtube channel - not sure there is anything new for you though:

   https://www.youtube.com/watch?v=7AigwDG2ZnU

The "SWD" debug header you are looking at is designed to work with Servo V2:

   https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/docs/servo_v2.md

Three key pieces of info copied from that page:

 1.  "Though Servo boards are not publicly distributed or sold (by Google), detailed information is available:

• Schematic
• Block Diagram + BOM + Schematic + Layout "

  2.  "Modern Chrome OS mainboards connect to Servo v2 with a 50-pin “Yoshi” flex cable. The schematic and layout for this cable is also available. The standard DUT-side debug header is an AXK750347G from Panasonic, though shorter variants are sometimes used."

  3. "The Yoshi Flex cable is used to connect Servo v2 to a servo header. The standard cable does not work with Serial Wire Debug (SWD), but a simple rework can be performed to support SWD." (rework instructions follow with photos).

Someone with more HW experience than I have might be able to sort out how to get serial console for TP-Link onhub with this public information.

  I've found what I think is the SWD debug port (still waiting on my usb -> swd stick to arrive in the mail to try it out), but am also just realizing that SWD isn't really designed to give you a console.

Based on the info above and the Oct 2021 updates to the OpenWRT thread, I'm hoping you have enough info to determine if you ordered the right HW or not. 

cheers,

grant