u-boot in restricted environment: networking over serial

[Ahmad Fatoum]

Hi,

On 30.01.25 14:55, Ferenc Fejes wrote:
> Hi,
> 
> Is it possible to use the serial port for u-boot networking? For example, given
> a restricted environment where the FIT image is available with ethernet firmware
> and drivers, so it is not possible to boot it with DHCP boot since there is no
> networking. Or simply the ethernet NIC has no u-boot driver at all. For such
> cases, I assume ymodem is recommended to download and boot the FIT image.
> 
> However, experimenting with different images and debugging, it would be more
> convenient if serial could be used as both data and console channel. Is this
> possible?
> 
> A simple example:
> 1. ppp on the host machine, with IP forward, NAT, etc.
> 2. u-boot establish a ppp connection over serial to the host
> 3. u-boot starts a netconsole session to the host
> 4. user can use netconsole and wget to download images
> 
> I was thinking of PPP, but that's probably not supported by u-boot. Anything
> similar with RNDIS and USB CDC ACM?
> 
> Thanks in advance for any hint!

If you are willing to implement it, there's RFC 916 (RATP), which
addresses the use case of establishing a reliable communication link over
serial. We use it in barebox to mount remote file systems via serial.

If you were to implement the same support in U-Boot, you could reuse
the host-side bits without change (and take inspiration from the barebox
implementation of the target-side bits).

https://github.com/barebox/barebox/blob/master/fs/ratpfs.c
https://www.barebox.org/doc/latest/user/remote-control.html

Hope this helps.

Cheers,
Ahmad

> 
> Best,
> Ferenc
> 


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