Insight into lan78xx driver support for Pi

20 Jun 2021

Does anyone have any insight into lan78xx usb driver support for the Raspberry Pi?

I am attempting to use a Microchip PoE USB-C device to enabling networking to a Raspberry Pi4B. The work is part of a RoadTest for Microchip PoE to USB-C Power and Data Adapter .

A quick check with a command line lsmod shows no lan78xx driver. There is no /lib/modules/5.10.17-v7l+/kernel/net/usb to support the lan78xx as suggested in some posts I have found.

I did find this post https://wiki.seeedstudio.com/Dual-Gigabit-Ethernet-Carrier-Board-for-Raspberry-Pi-CM4/ and successfully completed the procedure for an Ethernet Port configuration.

A lan7800 module reference does appear for a command line lsmod after the install. The Microchip PoE USB-C lan7800 port is not detected when connected to the Pi. Still no reference to a lan78xx module appears in the directory structure.

The vendors site https://www.microchip.com/wwwproducts/en/LAN7800 indicates there has been support in the Linux kernel. My searches for Pi driver support has been limited. My understanding is lan78xx is a modules in the usb subdirectory when installed. I'm not seeing that for this kludge.

I'm thinking maybe I need a a dtsoverlay in the config.txt directory. Really not sure. I have gone as far as to load Ubuntu for the Pi to see if it is O/S related. That didn't prove fruitful.

I welcome any insight community members may have regarding network driver installs for the Pi. I will continue to hunt and peck to see if there is anything I have missed.

Top Comments

colporteur over 4 years ago in reply to Gough Lui

WOW!

I have to confess, I would never have found the reference on my own. I could write a novel, if I documented all the avenues I explored trying to find something that referenced the interface and how to get it working. I finally made this post after three days of trying.

On reflection it does give me a feeling of disappointment. Yes, it great there is an answer but I question how many people would find it. Worse how many people would get discouraged not finding a solution and abandon the effort.

I agree Microchip PoE is not tailored to the Pi world and maybe that market share is minimal for their interest. I have yet to do a fresh install and try your fix on my Pi. If Lou says it works, it works:)

I wanted to acknowledge your efforts in helping me solve the issue. My plan is to clearly document what is needed to make it work in my review. Your name will appear in the credits.

Man I enjoy being a member of the E14 Community!
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Gough Lui over 4 years ago in reply to colporteur

I actually got inspired to put it in based on this post:
https://www.raspberrypi.org/forums/viewtopic.php?t=246348#p1504603

- Gough
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colporteur over 4 years ago in reply to Gough Lui

I appreciate you sharing your insight. Based on my understanding of your past RoadTests, I'm confident nothing I contribute will overshadow your review.

I will suspend the current approach and use your suggestion of the config.txt settings after starting with a fresh install.

Your findings support what I later discovered. There is a lan78xx driver installed by default. A trip down compiling a kernel showed the module present in the .config menuconfig setup.

My seeed link attempt at installing the driver was not necessary. I clean boot of an O/S install and an lsmod|grep lan displays a usbcore lan78xx driver. I was looking for lan7800. The interface not being detected appears to have been the issue. I will use your details to confirm it.

Are you willing to share the knowledge of where you found the OTG setting? I spent considerable time looking for information. This guide https://github.com/thagrol/Guides/blob/main/ethernetgadget.pdf doesn't even mention to configuration.
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colporteur over 4 years ago in reply to Jan Cumps

I found this JC early in my exploration. I later discovered while looking at compiling a kernel a lan78xx driver is installed. The interface is not being detected on mine configuration.
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colporteur over 4 years ago in reply to skruglewicz

Yes.
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