Intended use of "model" property?

Intended use of "model" property?

[Marti Bolivar]

I'm trying to understand the intended use of the model property
in DT spec v0.4-rc1 ยง2.3.2.

Specifically, can "model" be a property in any node of the devicetree?
The spec seems to indicate so, but grepping around the DTS files in
Linux, it seems to be primarily used as a property of the root node, as
a model name for the entire device.

There are a few exceptions in Documentation/devicetree/bindings/, but
they are mostly in sound/, so it's not clear to me whether this is the
"model" I'm referring to here, especially since that isn't present next
to "compatible", "reg", and friends in dt-schema/meta-schemas/core.yaml.

Is "model" in the ยง2.3.2 sense meant to be a property of the root node
only, or can it appear anywhere with the meaning defined there?

Thanks.

Re: Intended use of "model" property?

[David Gibson]

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On Mon, Sep 12, 2022 at 01:18:08PM -0700, Marti Bolivar wrote:
> I'm trying to understand the intended use of the model property
> in DT spec v0.4-rc1 §2.3.2.
> 
> Specifically, can "model" be a property in any node of the devicetree?
> The spec seems to indicate so, but grepping around the DTS files in
> Linux, it seems to be primarily used as a property of the root node, as
> a model name for the entire device.
> 
> There are a few exceptions in Documentation/devicetree/bindings/, but
> they are mostly in sound/, so it's not clear to me whether this is the
> "model" I'm referring to here, especially since that isn't present next
> to "compatible", "reg", and friends in dt-schema/meta-schemas/core.yaml.
> 
> Is "model" in the §2.3.2 sense meant to be a property of the root node
> only, or can it appear anywhere with the meaning defined there?

It can be used anywhere, but it's relatively rare.  It's usually for
human interest rather than signifying anything to driver software
(that's what "compatible" is for).

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: Intended use of "model" property?

[Rob Herring]

On Mon, Sep 12, 2022 at 3:18 PM Marti Bolivar
<marti.bolivar-hR+23Fw+YnFSHonuZl5R5Q@public.gmane.org> wrote:
>
> I'm trying to understand the intended use of the model property
> in DT spec v0.4-rc1 ยง2.3.2.
>
> Specifically, can "model" be a property in any node of the devicetree?

Yes, but not like 'status' in that bindings must define using it.

> The spec seems to indicate so, but grepping around the DTS files in
> Linux, it seems to be primarily used as a property of the root node, as
> a model name for the entire device.
>
> There are a few exceptions in Documentation/devicetree/bindings/, but
> they are mostly in sound/, so it's not clear to me whether this is the
> "model" I'm referring to here, especially since that isn't present next
> to "compatible", "reg", and friends in dt-schema/meta-schemas/core.yaml.

Audio has a defined use for 'model' to provide a name for the 'sound device'.

It's not in meta-schemas/core.yaml simply because it's not appearing
in lots of bindings.

> Is "model" in the ยง2.3.2 sense meant to be a property of the root node
> only, or can it appear anywhere with the meaning defined there?

Even use in the root node is not terribly well defined. ePAPR
(starting point for the spec) defined it as a compatible like string.
On Arm, it's a more human friendly freeform string.

So I wouldn't encourage new uses.

Rob