Re: [PATCH v1 1/2] dt-bindings: trivial-devices: add toradex,lava-hat-spi

[Francesco Dolcini]

On Mon, Apr 20, 2026 at 06:10:08PM +0200, Krzysztof Kozlowski wrote:
> On 20/04/2026 18:02, Conor Dooley wrote:
> > On Mon, Apr 20, 2026 at 01:45:35PM +0200, Francesco Dolcini wrote:
> >> From: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
> >>
> >> Add a compatible string for the SPI loopback device present on the
> >> Toradex LAVA HAT test fixture.
> >>
> >> The Toradex LAVA HAT is a board used for automated hardware-in-the-loop
> >> (HIL) testing, it provides several test-related functionalities, and
> >> exists in multiple variants depending on the board it is mated with. The
> >> SPI function is implemented with a loopback on the MISO/MOSI signals.
> >>
> >> As the device can be fully described using only "compatible" and "reg",
> >> it is appropriate to list it under trivial-devices.yaml rather than
> >> introducing a dedicated binding.
> >>
> >> The SPI implementation is identical across all Toradex LAVA HAT
> >> variants, so a single compatible string is sufficient.
> >>
> >> Link: https://lore.kernel.org/all/20260310133254.GA51497@francesco-nb/
> >> Link: https://lore.kernel.org/all/20260316073547.11437-3-francesco@xxxxxxxxxx/
> >> Signed-off-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
> > 
> > Acked-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> > pw-bot: not-applicable
> 
> 
> Heh, let's wait. That's a test device, so it won't be ever used in any
> final product, right? So not in final DTS?

It will be used in various DT overlay, that I plan to send for
inclusion in mainline Linux kernel once we have a way forward. So yes,
there will be DTB files using it.

The need is to be able to test SPI with a mainline Linux kernel, so I am
looking for a solution that works in mainline Linux.

What is the reason to not wanting to have a DT overlay file for a test
device in the Linux kernel? I assume that I would not be able to have an
overlay included, if it uses a compatible that is defined in
incomplete-devices. This was my understanding from
https://lore.kernel.org/all/a3796f8b-f94c-4d0d-a0b9-b2970e43e28d@xxxxxxxxxx/

> Then why it's here? I think I directed previously to document it with
> the rest of test devices - in incomplete-devices schema?

Because, that would not allow to add it to any DT file, from my
understanding.

I linked here both the email thread in which we discussed the topic
before, and I understood it was ok to send it, given we have an actual
HW for it and we plan to submit DT to support it in mainline Linux.

I see we are running in circle, apologize for that.
What can I do so that we can move forward?

Francesco