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

[Krzysztof Kozlowski <krzk@kernel.org>]

On 21/04/2026 11:59, Francesco Dolcini wrote:
> 
>> 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.
> 
> Do this sentence means that I can send a DT file for inclusion in the
> Linux kernel using a compatible documented in incomplete-devices?

No. You will be testing a mainline DTS + load non-mainline overlay. So
your requirements of "mainline Linux" are fully solved. Overlay is
loaded by bootloader for example and thus your kernel is fully mainline.


> 
>> 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").
> 
> Let me get into more details here, before sending a new patch version.
> 
> We have various LAVA HAT devices, the difference is that they provide
> different features and a different layout, based on the actual carrier
> board they are mated with.
> 
> We have an "Aquila LAVA HAT", that can be mated with the "Aquila
> Development Board", and a "Verdin LAVA HAT", that can be mated with a
> "Verdin Dahlia Board".

Of course, because each device is specific so even the hat must be
specific, unless you have a standard connector like Arduino or RPi.

> 
> As an example, you can find the Verdin Dahlia DTS here,
> ti/k3-am625-verdin-wifi-dahlia.dts, that can be mated with the "Verdin
> LAVA HAT".
> 
> The SPI device on both "Aquila LAVA HAT" and "Verdin LAVA HAT", is the
> same, no differences. On the Aquila variant we
> have two instances of it, while on the Verdin we have only one instance
> of it.
> 
> So, would we need a compatible like this? 
> 
> compatible = "toradex,aquila-lava-hat-spi", "toradex,lava-hat-spi";
> 
> or
> 
> compatible = "toradex,verdin-lava-hat-spi", "toradex,lava-hat-spi";

Yes, assuming that verdin/aquila hat works for EVERY verdin/aquila
board, regardless what SoM or SoC you have there.

Verdin is a SoM family according to:
https://www.toradex.com/computer-on-modules/verdin-arm-family

and I doubt you can attach hat to a SoM. There is no connector on SoM
for the hat... so probably you have a board, like Dahlia.

Best regards,
Krzysztof