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

[Krzysztof Kozlowski <krzk@kernel.org>]

On 21/04/2026 10:38, Francesco Dolcini wrote:
> 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@toradex.com>
>>>>
>>>> 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@dolcini.it/
>>>> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
>>>
>>> Acked-by: Conor Dooley <conor.dooley@microchip.com>
>>> 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.

Then you need to document it properly and post the DTS.

Toradex LAVA hat is way too generic. No, single compatible string is not
sufficient, please read writing bindings.

Please define exact model and variants.

> 
> 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.

incomplete devices do not stop you from that.

But you don't get exceptions because you want to mainline your DTS. Your
need detailed hardware description and precise compatible per each exact
hat ("exists in multiple variants").

Best regards,
Krzysztof