u-boot in restricted environment: networking over serial

[Ferenc Fejes]

On Thu, 2025-01-30 at 11:04 -0600, Tom Rini wrote:
> On Thu, Jan 30, 2025 at 02:55:53PM +0100, 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!
> 
> Typically we use x/y/zmodem for sending data over the serial port in
> U-Boot as no, we do not have networking support via serial port. Thanks.

I see, thank you for the clarification.