linux-kernel - Re: [PATCH 1/2] dt-bindings: mailbox: add support for referencing controllers solely by node

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Message-ID: <20241219-recent-everyone-865b19864693@wendy>
Date: Thu, 19 Dec 2024 14:11:53 +0000
From: Conor Dooley <conor.dooley@...rochip.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
CC: Jassi Brar <jassisinghbrar@...il.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-samsung-soc@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<andre.draszik@...aro.org>, <peter.griffin@...aro.org>,
	<kernel-team@...roid.com>, <willmcvicker@...gle.com>,
	<daniel.lezcano@...aro.org>, <vincent.guittot@...aro.org>,
	<ulf.hansson@...aro.org>, <arnd@...db.de>
Subject: Re: [PATCH 1/2] dt-bindings: mailbox: add support for referencing
 controllers solely by node

On Thu, Dec 19, 2024 at 01:07:46PM +0000, Tudor Ambarus wrote:
> There are mailbox clients that can discover the mailbox channel ID at
> run-time. For such cases passing the channel identifier via DT is
> redundant. Add support for referencing controllers solely by node.

I don't really get your implementation, why not just allow #mbox-cells = 0?
That's what's done for things like fixed frequency clocks that only have
a single output.

Cheers,
Conor.

> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
>  Documentation/devicetree/bindings/mailbox/mailbox.txt | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/mailbox.txt b/Documentation/devicetree/bindings/mailbox/mailbox.txt
> index af8ecee2ac68..0c4295a62f61 100644
> --- a/Documentation/devicetree/bindings/mailbox/mailbox.txt
> +++ b/Documentation/devicetree/bindings/mailbox/mailbox.txt
> @@ -5,9 +5,10 @@ assign appropriate mailbox channel to client drivers.
>  
>  * Mailbox Controller
>  
> -Required property:
> -- #mbox-cells: Must be at least 1. Number of cells in a mailbox
> -		specifier.
> +Optional property:
> +- #mbox-cells: Must be at least 1. Number of cells in a mailbox specifier.
> +               The property becomes mandatory for the cases where the clients
> +               reference the controller via the mboxes property.
>  
>  Example:
>  	mailbox: mailbox {
> @@ -19,7 +20,11 @@ Example:
>  * Mailbox Client
>  
>  Required property:
> +Clients must reference the mailbox controller either via the mboxes or mbox
> +properties.
>  - mboxes: List of phandle and mailbox channel specifiers.
> +- mbox: phandle pointing to the controller. Used by clients that can discover
> +        the channel identifiers at runtime.
>  
>  Optional property:
>  - mbox-names: List of identifier strings for each mailbox channel.
> @@ -29,7 +34,13 @@ Optional property:
>  	  communication between the mailbox client and the remote.
>  
>  
> -Example:
> +Example using mbox:
> +	power-management {
> +		...
> +		mbox = <&mailbox>;
> +	};
> +
> +Example using mboxes:
>  	pwr_cntrl: power {
>  		...
>  		mbox-names = "pwr-ctrl", "rpc";
> 
> -- 
> 2.47.1.613.gc27f4b7a9f-goog
> 

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